FX vs DX

FX versus DX

It amazes me that people still don’t understand the relationship between FX and DX format sensors.

Millions of people across the planet think still that when they put a DX body on an FX lens and turn the camera on, something magic happens and the lens somehow becomes a different beast.

NO…it doesn’t!

There is so much crap out there on the web, resulting in the blind being led by the stupid – and that is a hardcore fact.  Some of the ‘stuff’ I get sent links to on the likes of ‘diaper review’ (to coin Ken W.’s name for it) and others, leaves me totally aghast at the number of fallacies that are being promoted and perpetuated within the content of these high-traffic websites.

FFS – this has GOT to STOP.

Fallacy 1.  Using a DX crop sensor gives me more magnification.

Oh no it doesn’t!

If we arm an FX and a DX body with identical lenses, let’s say 500mm f4’s, and go and take the same picture, at the same time and from the same subject distance with both setups, we get the following images:

D5A9517 2 900x600 FX vs DX

FX versus DX: FX + 500m f4 image – 36mm x 24mm frame area FoV

D5A9517 900x600 FX vs DX

FX versus DX: DX + 500mm f4 image – 24mm x 16mm frame area FoV

FXvDX 900x411 FX vs DX

FX versus DX: With both cameras at the same distance from the subject, the Field of View of the DX body+500mm f4 combo is SMALLER – but the subject is EXACTLY the SAME SIZE.

Let’s overlay the two images:

FXvDX2 900x600 FX vs DX

FX versus DX: The DX field of view (FoV) is indicated by the black line. HOWEVER, this line only denotes the FoV area. It should NOT be taken as indicative of pixel dimensions.

The subject APPEARS larger in the DX frame because the frame FoV is SMALLER than that of the FX frame.

FXvDX3 900x496 FX vs DX

But I will say it again – the subject is THE SAME DAMN SIZE.  Any FX lens projects an image onto the focal plane that is THE SAME SIZE irrespective of whether the sensor is FX or DX – end of story.

Note: If such a thing existed, a 333mm prime on a DX crop body would give us the same COMPOSITION, at the same subject distance, as our 500mm prime on the FX body.  But at the same aperture and distance, this fictitious 333mm lens would give us MORE DoF due to it being a shorter focal length.

Fallacy 2.  Using a DX crop sensor gives me more Depth of Field for any given aperture.

The other common variant of this fallacy is:

Using a DX crop sensor gives me less Depth of Field for any given aperture.

Oh no it doesn’t – not in either case!

Understand this people – depth of field is, as we all know, governed by the aperture diaphragm – in other words the f number.  Now everyone understands this, surely to God.

But here’s the thing – where’s the damn aperture diaphragm?  Inside the LENS – not the camera!

Depth of field is REAL or TRUE focal length, aperture and subject distance dependent, so our two identical 500mm f4 lenses at say 30 meters subject distance and f8 are going to yield the same DoF.  That’s irrespective of the physical dimensions of the sensor – be they 36mm x 24mm, or 24mm x 16mm.

But, in order for the FX setup to obtain the same COMPOSITION as that of the DX, the FX setup will need to be CLOSER to the subject – and so using the same f number/aperture value will yield an image with LESS DoF than that of the DX, because DoF decreases with decreased distance, for any given f number.

To obtain the same COMPOSITION with the DX as that of the FX, then said DX camera would need to move further away from the subject.  Therefore the same aperture value would yield MORE DoF, because DoF increases with increased distance, for any given f number.

The DX format does NOT change DoF, it’s the pixel pitch/CoC that alters the total DoF in the final image.  In other words it’s total megapixels the alters DoF, and that applies evenly across FX and DX.

Fallacy 3.  An FX format sensor sees more light, or lets more light in, giving me more exposure because it’s a bigger ‘eye’ on the scene.

Oh no it doesn’t!

Now this crap really annoys the hell out of me.

Exposure has nothing to do with sensor size WHAT SO EVER.  The intensity of light falling onto the focal plane is THE SAME, irrespective of sensor size.  Exposure is a function of Intensity x Time, and so for the same intensity (aperture) and time (shutter speed) the resulting exposure will be the SAME.  Total exposure is per unit area, NOT volume.

It’s the buckets full of rain water again:

sensor size exposure 900x297 FX vs DX

The level of water in each bucket is the same, and represents total exposure.  There is no difference in exposure between sensor sizes.

There is a huge difference in volume, but your sensor does not work on total volume – it works per unit area.  Each and every square millimeter, or square micron, of the focal plane sees the same exposure from the image projected into it by the lens, irrespective of the dimensions of the sensor.

The smallest unit area of the sensor is a photosite. And each photosite recieves the same said exposure value, no matter how big the sensor they are embedded in is.

HOWEVER, it is how those individual photosites COPE with that exposure that makes the difference. And that leads us neatly on to the next fallacy.

Fallacy 4.  FX format sensors have better image quality because they are bigger.

Oh no they don’t – well, not because they are just bigger !

It’s all to do with pixel pitch, and pixel pitch governs VOLUME.

pixelpitch 900x302 FX vs DX

FX format sensors usually give a better image because their photosites have a larger diameter, or pitch. You should read HERE  and HERE for more detail.

Larger photosites don’t really ‘see’ more light during an exposure than small ones, but because they are larger, each one has a better potential signal to noise ratio.  This can, turn, allow for greater subtle variation in recorded light values amongst other things, such as low light response.  Think of a photosite as an eyeball, then think of all the animals that mess around in the dark – they all have big eyes!

That’s not the most technological statement I’ve ever made, but it’s fact, and makes for a good analogy at this point.

Everyone wants a camera sensor that sees in the dark, generates zero noise at ISO 1 Million, has zero diffraction at f22, and has twice the resolution of £35Ks worth medium format back.

Well kids, I hate to break it to you, but such a beast does not exist, and nor will it for many a year to come.

The whole FX versus DX format  ‘thing’ is really a meaningless argument, and the DX format has no advantage over the FX format apart from less weight and lower price (perhaps).

Yes, if we shoot a DX format camera using an FX lens we get the ‘illusion’ of a magnified subject – but that’s all it is – an illusion.

Yes, if we shoot the same shot on a 20Mp FX and crop it to look like the shot from a 20Mp DX, then the subject will have twice as many pixels in it, because of the higher translational density – but at what cost.

Cramming more mega pixels into either a 36mm x 24mm or 24mm x 16mm area results in one thing only – smaller photosites.  Smaller photosites come with one single benefit – greater detail resolution.  Every other attribute that comes with smaller photosites is a negative one:

  • Greater susceptibility to subject motion blur – the bane of landscape and astro photographers.
  • Greater susceptibility to diffraction due to lower CoC.
  • Lower CoC also reduces DoF.
  • Lower signal to noise ratio and poorer high ISO performance.

Note: Quite timely this! With the new leaked info about the D850, we see it’s supposed to have a BSI sensor.  This makes it impossible to make a comparison between it and the D500, even though the photosites are nearly pretty much the same size/pitch.  Any comparison is made even more impossible with the different micro-lens tech sported by the D850.  Also, the functionality of the ADC/SNR firmware is bound to be different from the D500 too.

Variations in: AA filter type/properties and micro lens design, wiring substrate thickness, AF system algorithms and performance, ADC/SNR and other things, all go towards making FX versus DX comparisons difficult, because we use our final output images to draw our conclusions; and they are effected by all of the above.

But facts are facts – DX does not generate either greater magnification or greater/less depth of field than FX when used with identical FX lenses at the same distance and aperture.

Sensor format effects nothing other than FoV,  everything else is purely down to pixel pitch.

 

 

 

 

More Nikon D850 leaks

More leaked specs on the Nikon D850 – and it could be something of an imaging revolution for Nikon users after all.

D850 395x900 More Nikon D850 leaks

Screen grab of the Nikon Italy page that was live for about 5 hours yesterday, click to view full size.

According to the leaked specifications, the camera will be fitted with a back lit sensor and gapless micro lens technology.

If this is true, then all the scathing I gave the Nikon D850 specs last week may need to be ‘dialled down’ a bit – the one thing this camera will NOT BE (again,if the tech leak is true) is a pumped up FX version of the D500.

What is a back lit sensor?

You can regard all Bayer pattern CMOS sensors in your dslr and mirrorless cameras as front lit.

Light leaves the rear element of your lens and strikes the sensor, passing through the micro lenses first, then a wiring/connectivity layer, and finally it strikes the photo diodes/photosites.

sony backlit cmos sensor cross section 02 More Nikon D850 leaks

Front lit (left) and Back lit (right) sensor layout.

Light can scatter within that wiring layer, and the distance between the micro lenses and the photo diodes effectively narrows their viewing angle.

Having the photo diodes directly behind the micro lenses removes the scattering potential, and increases the diode viewing angle – a bit like putting your eye closer to a key hole – you see more.

A back lit tech sensor may well have a 50% or larger diode/photosite ‘view angle’ than its front lit counter part with the same mega pixel count.  Couple that with new micro lens technology to remove the interstitial gaps, and there is a lot of potential for increased performance in terms of:

  • Native gain/light gathering during the exposure
  • Increased Dynamic Range over the Nikon D810
  • Increased Dynamic Range over the Nikon D500
  • Increased high ISO performance over both the D500 and D810
  • Dare I say it, lower diffraction values?  Surely the Circle of Confusion has got to increase in size – I don’t know for certain but it would definitely be interesting to find out.

Back lit/backside illuminated/BSI CMOS sensor tech is out there already – the Sony A7R2 springs to mind.

At the begining of this post I said the D850 could be something of an imaging revolution for Nikon users – and I meant it.

It’ll be the first Nikon FX DSLR (as far as I’m aware!) to be fitted with BSI tech, but if they screw up the ADC/SNR side of things like they did with the D5, then it’ll amount to NOT A LOT.

If however, Nikon do a good job of converting the analogue output of this sensor to a digital file, then we could say that no Nikon FX digital camera has ever been capable of delivering the potential benefits of the D850.

But we are still waiting for the official release of the specs so who knows…!

 

 

 

August News – Nikon D850 Thoughts

 Nikon D850 – Initial Thoughts.

2 900x506 August News   Nikon D850 Thoughts

Before we get into my initial thoughts about the D850 “leaked specs”, Roger Styles read my D5 post from the other week and asks:

“Very interesting…and I wonder if you would care to suggest how the D500 with a 300mm f4 lens would have performed? Similar? Worse? or heaven forbid better?”

Well Roger, all I can say is that I’m not really in a position to comment on how the MultiCam 20K system worked out on the D500/300mmPF combo (I didn’t use it) but I do have  D4S, D5 and D500 7200ISO shots so you can compare the image quality with regard to noise etc:

D501122 900x600 August News   Nikon D850 Thoughts

Nikon D500, 300mm f4 PF, 1/2500th @ f8, ISO 7200. Click to view full size

D5A8309 900x600 August News   Nikon D850 Thoughts

Nikon D5, 500mm 1/2000th @ f8, ISO 7200. Click to view full size

4SB0435 900x599 August News   Nikon D850 Thoughts

Nikon D4S, 400mm f2.8 1/2500th @ f8, ISO 7200. Click to view full size

Bare in mind I’m only illustrating IQ here – so look at the out-of-focus areas and darker tones to see the differences.

Roger – I can’t offer you any real comparisons between the D5 and D500 AF performance,  but from other tests I’ve done with the D500/300PF combo I’d say it performs the same or slightly better than the D5.  But only because you are using a shorter focal length lens with theoretically greater depth of field for any given aperture and distance – therefore more AF errors are masked by DoF.

Why does the D500 image look so crappy?

The answer is simple – too many mega pixels and not enough light!

The more megapixels you squeeze into a fixed area, the smaller each one of those photosites has to be.

There are two main problems with making photosites smaller:

  1. Reduced Dynamic Range
  2. Increased Diffraction

Overall, the sensor becomes more light-hungry.

Let’s put these three sensors on an even playing field with regard to crop factor:

D4/D4S = 16MpFX = 8Mp x1.5 crop

D5 = 20.8MpFX = 10.4Mp x1.5 crop

D500 = 20.9Mp x1.5 crop = 41.8MpFX

The IQ implications of these figures are illustrated in the images above!

And this brings me nicely around to the new Nikon D850.

maxresdefault 900x506 August News   Nikon D850 Thoughts

I got rather excited about the idea of this camera when it was first thought to have a hybrid OVF/EVF – the implications for using the plethora of super-sharp older manual lenses with modern focus-peaking in an EVF made me go all swoony!

But alas, this was not to be, and instead, all we have is a pumped up FX D500 – if the leaked specifications are to be believed.

The D850 is NOT a replacement for the D810 – anyone who thinks that is an idiot.

Let’s look at these leaked specifications:

  • 45.75MP FX full frame CMOS sensor – clipped Dynamic Range then, nice one Nikon
  • 180,000 RGB sensor that’s same as the D5, with better face detection and enhanced scene recognition – really?
  • Native ISO range of 64-25600 (expandable to 32-108400) – meaningless at the top end, and I doubt the base ISO will actually be 64ISO
  • 153-point AF system with 30% more frame coverage than the D5 – a higher resolution sack of angry weasels!
  • Center AF point -4EV, and all others -3EV – same as the D5
  • 8K timelapse shooting – Who in their right mind shoots time lapse and allows the camera to process and assemble it? Oh yeah, that’s right – dickheads!
  • 4K UHD video recording in FX with no crop – pass
  • 51-photo buffer when shooting in 14-bit uncompressed RAW – GOOD. That’s really a data-pushing miracle, to be honest
  • 3.2″, 2.36-million-dot tilting LCD touchscreen with improved gesture control – tilty screens are useful but straight away are a weak point.  But what use is gesture control when you’ve got gloves on ‘cos it’s -30 below?
  • 7fps continuous shooting standard, 6fps with autofocus, 9fps when using a battery grip – here’s where the price tag will go over £4000, because the grip will be £400 plus if I know Nikon!
  • 30fps at 8MP using the electronic shutter – 8Mp raws from a 48Mp sensor – what a spiffingly top notch idea.  And is that 30fps available silently?
  • RAW can be small, medium, and large resolutions – For F***s SAKE WHY would you buy a huge capacity camera and then shoot small files with it?  Has the world gone bloody mad?
  • 0.75x magnification viewfinder, the first for a full-frame DSLR – GREAT, but you can buy an adaptor to do the same thing to the majority of existing Nikons.
  • Focus stacking. The camera can shoot up to 300 photos with 10 levels of bracketed focus from nearest to infinity for software to stack afterwards – I have every confidence that this will turn out to be crap!  It’s a gimmick to get the unskilled to part with their money.  Aimed at macro and landscape photographers who can’t be bothered to tweak their focus manually.
  • Natural Light AWB achieves better white balancing in natural light – stupid gimmick
  • Completely silent electronic shutter while shooting in live view. – could be useful for sports if it works with fast shutter speeds
  • There’s no low-pass filter – GOOD – why couldn’t they do that on the D5?
  • SD + XQD card slots – Jesus Christ – Nikon need to grow up and stop mixing media

So as I’m sure you can tell, the Nikon D850 is not setting my world on fire.

What could Nikon have given us?

A hybrid OVF/EVF with an RGBW sensor and keep the capacity down to 36Mp or a tad less would have made a good impression with me for starters.

You have to have been asleep for months to not have heard something about the Fuji GFX medium format.  That’s running at 51.4Mp on a 1441mm2 sensor, which is roughly 1.67x the area of an FX 35mm camera.

Simple maths tells us that if we trimmed the GFX sensor to fit in a 35mm DSLR then it would be – that’s right, 30Mp.  The world of photography is populated by frigging idiots who just keep clamouring for more megs – and the camera manufacturers give them what they ask for simply because the idiots spend money like it’s going out of fashion.

Listen, if you want 50 megapixels or more, then go and buy a medium format camera and get 50 megs worth of good dynamic range with nominal diffraction.

Do not buy a Nikon D850 then stick a wide angle lens on and stop down to f22 – the image will be unusable at full resolution – and I don’t need to see a raw file to know that; it’s simple physics.

How this camera will stack up on the sports/action/wildlife front remains to be seen, but I don’t see how it can even be as good as a D5 – and that’s not brilliant.

To get the full potential out of the D850 for sports/action/wildlife then you will need the vertical grip AND an ENEL18A battery or two, and a charger, because I don’t think the D850 has USB charging.

An ENEL18A battery at Park Cameras is £169.00 and a genuine MH-26a charger is crazy money anywhere!

So you will be looking at more than £4000 – and I can think of far more sensible ways to spend that lump of cash.

Nikon promised us something really special to celebrate their 100th aniversary – this ain’t special Nikon!  It’s nothing more than the DSLR equivalent of a click-bait video.

But then again, I’m going on “leaked specifications” – and they could all be lies, smoke and mirrors.  We will have to wait and see what the real specs are when Nikon officially announce the D850.

 

Irix 15mm Blackstone f2.4 – First Night Test

 Irix 15mm Blackstone f2.4 – First Night Test

As I said way back in my in-depth review of this awesome bit of kit, I was originally interested in the Astro photography potential of the Irix 15mm Blackstone/Firefly lens.

Monday night – 24th July – saw myself and Rik heading for Snowdonia in North Wales, and in particular the small wooden foot bridge over Afon Idwal, just a ways up the old miners track behind Ogwen Cottage.

The weather forecast was for clear skies, and Google Earth in conjunction with Stellarium and TPE told me that around 11 pm the Milky Way would be over said small wooden bridge.  So we packed a few things and off we toddled.

D4D6145 3 2 2 2b 589x900 Irix 15mm Blackstone f2.4   First Night Test

IMPORTANT: THERE IS NO SHARPENING ON THIS IMAGE. All 33 image frames (32 light frames plus the long exposure frame) had ZERO sharpening applied during processing. The Milky Way towers high in the night sky over the mountains of Snowdonia in North Wales. A small wooden footbridge over the rushing waters of the River Idwal forms the focal point.

The place was rammed with people coming down off the mountains – and a pile going up as well – as it transpires, they were having an all-night party on the shores of Llyn Idwal higher up the track – nutters!

The Welsh midges were out in force and doing their best impression of man-eating tigers and guess who forgot to bring the mozy repellent!

The composition I was after entailed me setting up on the path and shooting straight along the bridge,  so I set the camera up with the Irix 15mm Blackstone set on the infinity click stop and the focus locked with the locking ring.  I knew from all the testing I’d done that this would give my tack sharp stars even with the aperture wide open and that stopping down to f6.3 or narrower would render a sharp foreground to around 1.5 metres.

The ‘plan’ was to shoot a foreground image at low ISO during twilight in order to save having to shoot a long exposure with LENR under total darkness – and that’s exactly what I did, then it all went a bit ‘Pete Tong’!

What caused the confusion was my Photpills app on my iPhone telling me that the Milky Way was already where I needed it to be in about another hour and a half, so the whole shot was not going to work – bear in mind the sky is still too bright to see any stars.

So like an idiot I believed it and moved the camera, looking for another composition that would work – as it transpired a fatal mistake.

A lesson for the future – if a mobile app does not match up with Stellarium, the Photographers Ephemeris and Google Earth try restarting the phone and re-calibrating the compass!!

After 45 minutes of struggling to find another composition using the new projected position of the Milky Way in the growing darkness, I looked up and saw the Summer Triangle – in exactly the position that my original plan had calculated.

After a short bout of self-directed expletives based around men’s dangly-bits and the act of procreation, I got the camera back in something approximating its original position, but of course, the original framing would be ‘off’ so my initial low ISO foreground shot was useless.

Starting over, I set the camera to shoot 32 frames in continuous low and used a locking cable release to shoot  rapid sequences of 32 frames – an easy way to do the job that does not always work too well with a big zoom like the Nikon 14-24, or Canon 16-35 – occasionally you can get ‘mirror vibration’ effects on your images.  But with a short-barreled prime like the Irix 15mm, this is not a problem I ever see.

By around 11.30pm I’m happy with the sky shots I have in the can, but now comes the long exposure foreground shot.

I’m actually dreading this shot as it’s going to take a long time to produce and I’m anticipating some of those aforementioned party goers to come wandering back down the track with head-torches waving around all over the place.

I opted for a 10-minute exposure with long exposure noise reduction enabled in the camera – so the shot is going to take 20 minutes to produce.

Twenty minutes later, the shot on the back of the camera indicated that in reality, it needed around another stop and a half-ish of exposure time.  I’d got away with no torches wandering through this shot, but if I did another, longer one I was certain it would get ruined.

So I shot 32 dark frames and another couple of 32 frame sequences, then we packed the gear away and headed for home.

Screen Shot 2017 07 25 at 16.58.11 900x506 Irix 15mm Blackstone f2.4   First Night Test

The total number of frames for this shot with the Irix 15mm was 85 and comprise of:

  • 32 light frames 6secs @f4 6400 ISO
  • 32 dark frames 6secs @f4 6400 ISO
  • 1x 600sec @f6.3 400 ISO – (no need for re-focus so no focus breathing problems).
  • 20 frames to make the master flat file

(If you to learn why we shoot so many frames and what to do with them all then buy my latest Astro photography training video HERE).

stars100percent 900x858 Irix 15mm Blackstone f2.4   First Night Test

Made from 32 images with 32 dark frames and a flat-field frame by Starry Landscape Stacker 1.4.0. Click to view full size.

As you can see from the image above, stars are tack sharp (even with no sharpening added in post), and coma is minimal.  And most importantly there is plenty of colour in those fainter stars – something that is a little harder to achieve with the ubiquitous Zeiss glass.

I could improve the image quality even further by correct that minimal coma in Photoshop with a custom brush and the clone tool, and make a star mask and reduce the noise even more (see my training videos if you want to know more!).

And of course, if I hadn’t had the wobble over composition then perhaps I would have ended up with something like this:

D4D5907 2 600x900 Irix 15mm Blackstone f2.4   First Night Test

Or something in between the two!

But either way, the session proved to equal or exceed my expectations of this Irix 15mm lens capabilities.

So, am I impressed by how this lens performs under Astro photography conditions?  You bet I am!

I’ll never use my trusty Nikon 14-24 for Astro photography ever again as far as I can see – why would I…

Sharp focus with the Irix 15mm is so easy to achieve, and there is now no reason to re-focus on closer foreground objects – all I need to do is stop down the aperture a bit.  So that’s all those focus-breathing errors out the window for starters.

Then, there is less coma, less chromatic aberration and a lot less barrel distortion.

When fumbling around in the dark, personally I think it would be good if Irix could increase the diameter of the focus locking ring, but that’s such a minor point it’s only just barely worth a mention.

What’s next?

Irix have just sent me a set of their new Edge 95mm screw-in filters, including 10x and 7x ND filters and the circular polarizer – so some daytime landscapes seem to be in order over the next couple of weeks.

I just wish I’d had the 11mm for the shot of the Milky Way!

Nikon D5 Extended Test

Nikon D5 Extended Test

The last week in June saw me in Norway doing something a bit different from the norm – photographing eagles all week with a 500mm prime – real hard work!

But I thought the task would be made slightly easier with the Nikon D5 running with generation 2 firmware; that is v1.10

And after a solid week of shooting my verdict is – WOEFUL!

The auto focus is still as predictable and user-friendly as a sack full of weasels, but what I found truly appalling is the image quality at lower ISO values – and by lower I mean sub-3200 ISO!

D5A0836 900x600 Nikon D5 Extended Test

Click image to view full size

D5A0836crop 900x808 Nikon D5 Extended Test

Click image to view full size

Shooting in Manual Exposure/Auto ISO is the most efficient way of shooting any action, especially with long glass,  but allowing the Nikon D5 to choose its ISO speed just highlights its single massive drawback – poor low ISO performance.

The shot above is at ISO 250, 1/2000th sec and f8.  The crop shows the simple adjustments done to the shot inside the Lightroom Basic panel, and as you can see there is nothing untoward there.

But just look at that appalling level of noise in the underside of the wings – as I said before – WOEFUL.

In this next image, we see the same eagle shot at the same time with the D5 (left) and a D4S (fitted with a 400 f2.8, right). Both cameras are in d25 AF mode, 1/2000th sec, f8 and ISO 1100:

D5A7655 900x564 Nikon D5 Extended Test

Click image to view full size

Both images have had a ‘zeroed’ process applied to them in Lightroom followed by a process version swap to kill the excess contrast added by Lightroom in the background.

Again there is excess noise under the wing together with detail degradation in the D5 shot on the left.

As a final comparison, here is the same moment in time caught on the D5, D4S and 1DXMk2. All 3 images have a flat, neutralised process in Lightroom with no added output sharpening:

D5A7649 900x600 Nikon D5 Extended Test

Nikon D5, 500mm 1/2000th, f8, ISO 1600
Click to view full size.

4SB0284 900x599 Nikon D5 Extended Test

Nikon D4S, 400mm, 1/2000th, f8, ISO 1250
Click to view full size.

B39I9903 900x600 Nikon D5 Extended Test

Canon IDXMk2, 400mm, 1/200th, f6.3, ISO 640
Click to view full size.

You do really have to view these images at their full size.

On the whole, I have to say that the 1DXMk2 is the worst image in terms of IQ – both Nikons have it beaten to death – which I must admit surprises me considering the ideal lighting conditions.

But as for the two Nikon shots the D4S still produced the slightly better IQ, lens differences aside, there is still slightly more noise in the D5 shot.

The other error in the D5 shot is due to the sack of angry weasels – the auto focus – the shot is not sharp.  But funnily enough the previous frame was:

D5A7648 900x600 Nikon D5 Extended Test

Click to view full size.

As ever, the Nikon AF tends to bounce around a little bit. Even though the D5 has the new Multicam 20K system there is still the same problem of subtle focus bounce that I personally try and negate by shooting at f8 – hoping that the extended DoF will mitigate its visual effect.

But it doesn’t always work, and the D5 will still sometimes drop focus completely on the ‘pick shot’ when the eagle hits the water.

Over the course of the week, I tried pretty much every conceivable permutation of Blocked Shot Response/Subject Motion/AF Mode settings that made any sense – and a few that didn’t – and to be honest they were all as bad as each other.  In the end, I settled on BSR/SM settings at default ‘out the box’, and Group AF mode – but that was way less than perfect.

Ole Martins eagles do represent possibly the most testing scenario for any camera auto focus system, but overall I have to say that for this particular job the D5 AF is an epic fail and a retrograde step – the D4/D4S faired much better.

And both Nikon systems get kicked into touch by the Canon system,  but the IQ of the 1DXMk2 lets it down somewhat, especially in comparison to the Nikon D4/D4S.

I’m certain that better IQ can be had from the Canon system if only Canon would give its users a firmware update to record uncompressed raw; something I’ve been banging on about for years.

But this post is about the Nikon D5 image quality at lower ISOs – and in all honesty, it’s CRAP.

Further Nikon D5 AF thoughts:

Typically of Nikon, they bring out another firmware update just after I use the damn thing for a week.  I’ve not tried the new firmware yet but the ‘added AF modes’ of a single row and single column closest point have a certain smack of desperation in my eyes.

I know that OEM AF calibration is done in both the horizontal and vertical planes.  So to give a camera the ability to use its horizontal calculations and to ignore its vertical ones, and vice versa says to me that there is an imbalance between its x and y axis ‘workings out’.  Couple this with forcing the AF to pick the closest point on the subject under that row or column is basically a case of ‘hedging your bets’ even further.

Nikon should have done exactly what Canon did, and simply refine their existing AF system instead of adding a shed-load of these tracking sensors – there are just TOO MANY points resulting in too much information, and any errors between vertical and horizontal are just being amplified.

I cannot find any visual representation of the two new modes, called group-area AF (VL) with 5 points, and group-area AF (HL) with 11 points.  But if they are as described then they will be ignoring the fixed tracking points. If that is indeed the case, and these modes actually give a marked improvement, then the whole system is a waste of time and effort because it is the plethora of fixed tracking points that form the main distinction between the Multicam 3500 FX and 20K systems.

But hey, that’s just my opinion and I’m not really in possession of all the facts yet.

 

Irix 15mm Firefly Offer

Irix 15mm Firefly Offer for UK customers.

15mm firefly Irix 15mm Firefly Offer

Just had this info in from the Irix UK sales team:

IRIX 15mm f2.4 Firefly
**LENS SPECIAL**
Limited period offer – FREE Delivery in the UK
FREE Gelatin Filter Kit – contains 15 x Neutral Density Filters
List €475.00 Offer Price €451.25 (£395.00 approx.)
www.irixlens.com
register and enter this code to purchase: 5W1YJ62C

  • IRIX 15mm Firefly lens
    Full Frame Rectilinear lens
    Focus Locking Ring
    Hyperfocal Markings
    Infinity Click & Calibration
    Neutrino Coating
    3 Weather Seals
    95mm Filter & Gelatin Slot
    Removable Lens Shade
    Lightweight Polycarbonate
    Minimum distortion
    Canon, Nikon and Pentax fit
    2 Year Warranty
    Same optics as the Blackstone version

I have not seen a Firefly, let alone used one – and I’m a miserable old goat who can’t see the point in a light weight version of something so small as the Blackstone.  But I can definitely see the point of the money saving properties of a Firefly purchase!

Irix Blackstone 15mm f2.4 – update.

Lens Review – Irix Blackstone 15mm f2.4 update.

Some bad weather made us lose a day and a half in Norway last week and so the landscape opportunities didn’t arise as they were expected to do – eagle action takes precedence, and we certainly managed a lot of that.

But I had to grab a real world test shot sequence on a real scene.

Even though this lens had impressed the hell out of me up to this point, I wasn’t quite prepared for the spectacular performance it gave me.

Important: None of the images below have had ANY vignette or profile corrections added to them.

D4D3002 599x900 Irix Blackstone 15mm f2.4   update.

Perfect exposure for the highlights, the setting sun is creating an 18 point star as you would expect from a 9 blade aperture – and where’s the flare some reviewers are talking about?
Full resolution jpg from the original raw file with no post processing.
Click to view full size in new window.

Now let’s not mess about, let’s go 2 stops over:

D4D3004 599x900 Irix Blackstone 15mm f2.4   update.

Vestigial 18 point star due to the 9 blade aperture diaphragm and zero flare anywhere.
Zero enhancements and no added sharpening.
Full resolution jpeg, f16 and focused using the infinity click stop – it’s simpler than shelling peas.
Click to view full size in new window.

Now let’s turn the camera over and go the full 15mm AoV in the horizontal – this was the real eye-opener for me:

D4D3008 900x599 Irix Blackstone 15mm f2.4   update.

Check out the vertical lines of the planking on the shack, no flare around the cable stay, and the boat masts on the right edge of the frame.
It can’t get any better with a 15mm focal length.
Just a tiny amount of Lightroom adjustment brush in the deepest foreground shadows and nothing else.
Click to view full size in new window.

Just check out the perfect verticals on the boat masts at the right edge of the frame, and still those planks on the shack are vertical – it seriously doesn’t get any better than this with a super-wide.

We had a 300km road trip in a staggering 35 degree heat up to Stekenjokk in Sweden – Long-tailed Skuas and great landscapes says Ole.

So we get there – no skua, they’ve all mysteriously vanished a few days before, so it was decided we’d force Ole to drive all the way back again to get a boat trip for eagles in the early morning – he wasn’t happy doing 600kms with an hours break but it serves him right!

But there’s a real gem of a shot to be had under a road bridge across the Gaavesjohke river:

D4D3834 2 2 599x900 Irix Blackstone 15mm f2.4   update.

Heading back south on the 824 road there’s a turn on the right and a bridge over the Gaavesjohke River. This is taken from rocks underneath said bridge.

Taken at 11.30pm 29th June, it’s not the best processing but it still serves to prove my point about the Irix Blackstone 15mm f2.4 lens:

  • 1/8th sec @ f16 and ISO 100.
  • Infinity click-stop focus.
  • Compose in Live View.
  • Close the viewfinder blind.
  • Turn off Live View.
  • Engage Mirror Up shooting and hit the remote release once, wait 5 seconds and hit it again.

Seriously, it’s like operating a point-and-shoot!

There’s no messing about doing differential focus, just turn the focus ring until you feel the ‘click’ and take the shot – simple.

I’m just waiting for some Irix filters to turn up and I’ll be off to North Wales for the day.  With a bit of luck we’ll shot a demo video or two so I can talk you through how easy this lens is to use.

Message to IRIX: please send filters ASAP!

Latest News

Apologies all – I know I’ve been a bit quiet for the last 4 weeks, but I’ve been busy with a few things.

Ive just finished my new video training title – the Complete Guide to Photographing and Processing Night Sky Images.

Screen Shot 2017 06 20 at 08.14.59 900x506 Latest News

Topics covered throughout the video training lessons include:

  • Focusing at Night
  • Camera settings
  • Correct shutter speed for your focal length, sensor size and latitude
  • How many frames to shoot
  • When and when NOT to use long exposure noise reduction in your camera
  • Correct neutral white balance in Lightroom
  • Lightroom sharpening & Noise Reduction settings
  • Shot Noise & Fixed Noise
  • Stacking & aligning stars to reduce SHOT noise in Starry Landscape Stacker and Photoshop
  • Manual star alignment in Photoshop – the way that actually works!
  • Masking using the Image Calculations Panel inside Photoshop
  • Normal brush masking in Starry Landscape Stacker
  • Using precise masks made in Photoshop inside Starry Landscape Stacker
  • Photoshop layer masks, layer blend modes, layer groups & group masks
  • Retouching image layers & masks in Photoshop
  • Photoshop Smart Objects & the Camera Raw smart filter

and more.

Over 7.5 HOURS (465mins approx:) of video training spread over 43 lessons that I GUARANTEE will make you an excellent photographer of this most enigmatic natural wonder.

You wouldn’t believe how long it takes to produce these video training lessons when you work on your own with a shoe-string setup!

Click the link above if you shoot landscapes and fancy a crack at proper night sky photography – once you start you won’t be able to stop – it gets very addictive!

Anyone who bought my original ‘Basic Milky Way Workflow’ training can email me and get a discount code, as the new title incorporates re-worked versions of the videos they already have, plus 30 new lessons.

In between bouts of recording videos I’ve been testing a lens that’s had me intrigued ever since I heard about it early this year.

I’m talking about this little baby:

D4D1060 2 2 Latest News

Yes, the Irix 15mm f2.4 Blackstone.

And I have to say that it’s impressed me – greatly.

lenscomp Latest News

I decided to test it against two of the most expensive and respected lenses in the same focal length group I could think of – the Nikon 14-24 f2.8 zoom and the hugely expensive Zeiss 15mm f2.8 Distagon ZF2.

Nope, no Rokinon/Samyang/Tamy/Tokie/Sigy glass comparisons as this Irix is something of a cut above, if you get my drift.

I’m off to Norway on Saturday for a week, but when I get back I’ll finish the review of this cracking bit of kit – suffice to say this Irix is having a trip to Norway on Saturday, and it won’t be its last!

If you want any info on this lens in the meantime just email Mr. Irix in the UK – Charles Woods at info@actionmc.co.uk

And speaking of Norway, I’ve decided to be different on this eagle trip and shoot using the Nikon D5 and a 500mm f4 prime (the heavy one).

Am I making a mistake – who knows, but I am taking the trusty D4 – just in case!

Lens Review – Irix Blackstone 15mm f2.4

Irix Blackstone 15mm f2.4

D4D1060 2 2 Lens Review   Irix Blackstone 15mm f2.4

I heard a few rumors about the new Irix lenses before I went to Iceland back in March, but could I find one to even look at let alone test – no, they seemed as elusive as hens teeth.

But last month I was invited by the Irix marketing and distribution team to give one a beating!

The one lens in the range that piqued my interest the most was the Irix Blackstone 15mm f2.4 – and here’s why:

  1. F2.4
  2. Supposed lack of CA
  3. Supposed lack of barreling
  4. 15mm PRIME
  5. Focus locking ring
  6. Hard focus stops
  7. Infinity click/detent
  8. Good old-fashioned engraved focus scale with DoF, IR and hyperfocal markings
  9. Solid all-metal construction
  10. Removable lens hood – the importance of this will be pointed out later.
  11. Price point – for the money this lens COULD represent epic value for money – but only testing & evaluation will confirm that.

All-in-all the lens appeared to be a dream for wide-field astro photography and sweeping vista landscapes – just such a shame I couldn’t get hold of one for my Iceland trip.

So a couple of weeks ago I met up with Charles Woods of Charles Talks fame – a real nice guy who moves in far higher circles than I do being the go-to contact for Leaf, Cambo and many other gorgeous lines of photographic loveliness.  If Charles takes on a brand then it’s worthy of some very serious considerations.

The Lens:

The Irix Blackstone 15mm f2.4 packaging is like a babushka – it’s a lens in a semi-rigid case, in a tin, in a box! (excuse the slightly dog-eared box but it’s been around a bit!).

Inside the tin you will also find a world-wide warranty card, a multi-lingual introduction booklet – AND, a SPARE rear lens cap; a nice touch Irix.

15mmPak Lens Review   Irix Blackstone 15mm f2.4

Open the zipped case and there is your lens with the lens hood reversed:

15mmPak2 1 Lens Review   Irix Blackstone 15mm f2.4

Remove the lens, turn the lens hood around, line up the registration lines on the hood and lens, then twist until it locks into position:

15mm Lens Review   Irix Blackstone 15mm f2.4

A couple of interesting features on the lens you MAY find useful:

15mmPak3 Lens Review   Irix Blackstone 15mm f2.4

On the underside of the lens hood (if it’s on the top you’ve got the hood upside down) you will see a sliding door.  If you push this forward it will reveal a gap  – fit a 95mm screw-in polarizer and you can rotate it as necessary then slide the door back until it ‘clicks’ shut.

And on the rear of the lens there is a built-in gelatin filter holder – Irix have put a lot of thought into the ‘bells & whistles’ on these lenses.

My Thoughts – personally I have to say that these two features may well be very useful for studio/indoor photography BUT – try fitting tiny gelatins in a force eight gale when shooting landscapes!  And as for polarizing filters – they never really work well on lenses with such a wide angle of view because their effects are virtually non-existent on all but the center of the image.

It’s vitally important that the filter access door is ‘clicked’ closed, otherwise it can cause a small amount of flaring – I’ve taped it on the outside so I can’t open it by accident, and I’ll be using 150×150 filters and a 95mm adapter ring for the holder.

Being a bit ‘old skool’ I’m never a big fan of light weight plastic lenses if truth be told,especially when it comes to wide angles. So holding the Irix Blackstone 15mm f2.4 is a real pleasure for me with its all metal construction, and honestly, it’s built like a tank.

The lens itself is manual focus only and available in Nikon F, Pentax K & Canon EF mount options, and features a 9 curved-blade aperture together with 15 elements in 11 groups.

15mmElements 1 Lens Review   Irix Blackstone 15mm f2.4

The focus ring is silky smooth and has more resistance than your typical Zeiss Distagon, which in my opinion is a good thing.  The other attribute of the focus ring is the long throw, which is a lot longer than the 15mm Distagon and comparing it to the short throw, fast focus ring on the venerable Nikon 14-24, this Irix lens should be a dream to use for both daytime and night landscape photography.

I have to add a note here about the focus ring on the Nikon 14-24.  It is far too fast/short for precise manual focus without a heck of a lot of practice.

Focus Scale & Focus Locking Ring:

15mmPak4a Lens Review   Irix Blackstone 15mm f2.4

Just ahead of the main focus ring is the focus locking ring – one of the main features of the lens I found piquing my interest in the first place, especially for wide-field astro work where focus is super critical, and accidental movement of the focus ring easily happens.  In the image above the focus is not quite fully unlocked – the unlock indicator should be just about in line with main focus indicator line on the focus scale/vertical white line after the ’15’ on the lens bell for normal focus operation.  Turn the locking ring to the left until it stops – don’t over tighten/force it – and your focus is locked.

The focus scale itself is excellent, and packed with all the information you could ever need if truth be told.

There is a definite ‘click’ as you focus at infinity, and there is even an infra-red focus mark.  You have DoF indicators for f8, 11 & 16 together with hyperfocal distance markings for the same apertures.

There is also one more feature of this lens that I have not mentioned yet, and that’s because it isn’t something you should really ‘mess about’ with unless you know what you are doing!  I am talking about this on the underside of the lens bell:

15mmPak4b Lens Review   Irix Blackstone 15mm f2.4

Details of how to use this feature can be found on Page 8 of the downloadable Extended User manual HERE.

My Thoughts – just about every manufacturer of lenses of this focal length will do a ‘factory infinity calibration’ calculated at beyond 50 meters.

As a landscape photographer your eye level horizon at sea level is around 4700m, and the clouds touching the horizon may be well over 100km away.  Focused at infinity and stopped down to f11 or f16 they WILL be sharp due to DoF.

However, shooting the sky at night at f2.4, f2.8 – in other words with NO DoF to help you out – you will invariably find that you need to focus just before, or more rarely just after, the infinity mark in order to get those stars tack sharp.

A close star like Arctaurus is more than 36.5 light years away, and Polaris – the Pole Star here in the northern hemisphere – is 433.8 light years away.  What I’m trying to say here is that there are many ‘degrees of infinity’ and some types of photography require greater accuracy than others.

Experience has taught me that at 14mm and f2.8 sharp focus on street lights at night from around 15km and an elevated position work perfectly for pin-sharp stars.  Some people then tape the lens focus ring, but using the focus locking ring on the Irix is a tidier solution.

But Irix go a step further than that and give you the ability to MOVE the position of the infinity indicator to correspond with a true visual infinity.  PLEASE READ the manual before attempting to do this yourself.

So this Irix Blackstone 15mm f2.4 is perhaps the most well-appointed lens I’ve ever come across – but now it’s time for the rubber to meet the tarmac and actually do some testing.

Comparative testing

It made sense to compare the Irix Blackstone 15mm f2.4 to possibly the best known and more expensive lenses in this super-wide lens class, namely the Nikon 14-24mm f2.8 and the Zeiss Distagon 15mm f2.8 ZF2.  There seemed very little point in comparing the Irix to the likes of the Rokinon/Samyang 14mm prime as I would expect the Irix to out-perform it by a good stretch, and thus not show how far the Irix ‘punches above its own weight’.

I’ve been wanting a prime to replace the Nikon 14-24mm, especially for night sky photography, for quite some time.  To that end I have tried three different examples of the Samyang 14mm f2.8 and found them all terrible with the aperture wide open when used on a 36Mp camera.  The images from it might appear okay shrunk down to 1920 x 1080 and run in a time-lapse video, but for full resolution stills and large display prints I have found all three examples I have tried to be inferior in terms of sharpness and coma.

lenscomp Lens Review   Irix Blackstone 15mm f2.4

So having decided on the two comparison lenses my first test was for vignetting.

Vignette Test Results:

The images below were all produced using the standard DSO Flat Frame production technique of imaging a diffused D65 light source with the lens focused at infinity.

(Click the image to open in a new window and click again to view at full size)

15mmBlackstoneVigTest 1 Lens Review   Irix Blackstone 15mm f2.4

Vignette testing the IRIX 15mm Blackstone lens against the Zeiss Distagon 15mm f2.8 ZF2 and the Nikon 14-24mm f2.8 @15mm. (Click the image to open in a new window and click again to view at full size).

Now before anyone gets ‘all hot and bothered’ about the vignetting on the Irix at wider apertures, here’s where the advantage of a removable lens hood comes into play.  Taking the lens hood off after you have produced your image enables you to easily produce a flat calibration frame using an LCP filter – something that the medium and large format photographers have been doing for years.  Combining these frames is easy inside the likes of Lightroom, and the process removes all vignetting, colour shifts and dust spots from your images.

Of course, you can produce flat calibration frames for the likes of the Nikon or Zeiss – I do it all the time – but you have to make them in the same manner as I made the test shots above.  But it is imperative that you shoot them at the same focus distance, ISO, focal length and aperture as your image frames.

But using the Irix makes the process very simple and it takes just a few seconds to produce a calibration frame which is customized for your composition and lighting levels.

So despite what you might think, vignetting is irrelevant – especially on lenses with a removable lens hood.

Sharpness & Diffraction, Resolution, Chromatic Aberration, Native Lens Color Cast & Contrast Testing.

Please make sure you view these images at 100% magnification by clicking on them.

This test was carried out at a focus distance of 12.5 inches and lacking a proper test bed, getting everything parallel and centered was quite time-consuming I can tell you!

All images shot in manual mode at ISO200 using shutter speeds that rendered a +/-0Ev on the cameras internal meter.

There are some subtle exposure variations between shots from the same lens in each of the three tests which is due to the use of cold cathode lighting, its flicker frequency and the shutter speeds used, but the variation is negligible and for our purposes totally irrelevant.

There has been no sharpening, CA correction, luminance or color noise reduction or other process settings applied to any of the images you see below except for white balance.

The first set of images show the low right optical center 770 pixel square from the D800E raw files.  The second set of images show the same 770 pixel square from the bottom left corner of the frame, and the third set that of the top center.  I chose the low right center because we are interested in the rendering of the higher lpm (line pairs per millimeter) resolving power of the three lenses being tested.  The axial center is located in the middle of the concentric circles:

Centers Lens Review   Irix Blackstone 15mm f2.4

Sharpness & Diffraction, Resolution & CA, Native Lens Contrast & Colorcast test results.
Image Center Low Right
Camera used: Nikon D800E.

Immediately one or two things are apparent.

The Zeiss is the sharpest at apertures wider than f5.6, and both the Nikon and Irix catch up with it by the time we get to f8.

So above (wider than) f8 the Irix would appear to be less sharp than the Zeiss – but things are never quite so cut and dried as they appear.

The Zeiss is not quite as sharp as you think because it’s got a higher degree of transmitted contrast – something a lot of people would be mistaken in thinking is due to the so-called ‘Zeiss pop’**.  If I remove -20 contrast from the Zeiss f5.6 image and equalize the black and white greyscale values in Photoshop, then the difference between it and the Irix at f5.6 appears to be significantly less than we first thought:

Zeiss equalise to Irix Lens Review   Irix Blackstone 15mm f2.4

Zeiss Distagon @ f5.6 (left0 vs Irix Blackstone @ f5.6 (right) with black point and white point greyscale values in the Zeiss image modified to closely approximate those of the Irix image.

** the so-called ‘Zeiss pop’ is down to sublime MICRO-CONTRAST, and the 15mm Distagon has very little of it.  You need to look at Zeiss lenses longer than 25/30mm before you even begin to see it.

And the Nikon exhibits the same tendency, though not as extreme as the Zeiss.

So all in all, from an image center sharpness point of view the Irix has good level of performance.

The Irix seems to consistently produce a ‘warmer’ image at f2.4 than at f2.8 and beyond, which is a bit odd, but again easily correctable in post so not of any real concern – unless you are crazy and shooting jpeg-only of course.

The next observation we can make is image center CA.  All 3 lenses exhibit good anti CA in their image centers, but if you look carefully you will see that the best performer is the Irix.  The Zeiss is second best, and the most obvious CA can be seen on the Nikon images.

Diffraction:

On the diffraction side of things we can see diffraction begins to show at apertures smaller than f11.  But diffraction is caused by the inter-relationship of lens aperture Airy Disc and sensor CoC (circle of confusion).  As long as the lens aperture Airy Disc is SMALLER than the sensor CoC, diffraction will not be a problem.

When the Airy Disc and sensor CoC are of equal size the combination of lens and camera sensor is said to be at its ‘diffraction limit’.

These images were produced using a 36Mp Nikon D800E, which is diffraction limited to f14 at best, and more usually f13.  Switching out to a 20Mp Nikon D4 I’m diffraction limited to f16 or 18, and on a 12Mp D3 I can get away with f20.

So diffraction has little to do with the lens and everything to do with the camera sensor, and if I had used a Nikon D3 for the above tests then f22 on all 3 lenses would look a lot sharper!

Lens Native Color Cast:

We can also just about see the Zeiss has a vestige of a green cast, and the Nikon a slight blueish one while the Irix stays fairly neutral (other than at f2.4).

The CA/Color & Resolution story takes on a whole different meaning though when we move off-axis and look at the image sides and corners:

Sharpness Diffraction Resolution CA Native Lens Contrast Colorcast Nikon D800E Image lower left corner Lens Review   Irix Blackstone 15mm f2.4

Sharpness & Diffraction, Resolution & CA, Native Lens Contrast & Colorcast test results.
Image Lower Left Corner
Camera used: Nikon D800E. (Click the image to open in a new window and click again to view at full size).

Between the Nikon & Zeiss that’s £3500 worth of glass at f2.8 out-performed by a much cheaper lens at f2.4 – gives you something to think about doesn’t it.

Now let’s take a look at the top center:

topmid 1 Lens Review   Irix Blackstone 15mm f2.4

Sharpness & Diffraction, Resolution & CA, Native Lens Contrast & Colorcast test results.
Image Top Center
Camera used: Nikon D800E. (Click the image to open in a new window and click again to view at full size).

In both of the off-axis comparison tests you can easily tell which lens is the winner in the CA stakes – the Irix, and by a huge margin too.

Yes it does exhibit some CA at the image margins, but far less than the other two lenses.

CA removal can sometimes have a detrimental effect on convoluted edges in your images due to the manner in which it works.  Ordinarily these errors don’t have much of a visual impact in your shots, but the larger your sensors pixel count the more edge-halo problems you can experience if you try the sharpen the image, or try to create or apply masks.  I shall talk more about this later.

The inherent ‘native’ color cast of the Nikon and Zeiss lenses is plainly obvious in the off-axis test shots, as is the neutrality of the Irix.

Something else you may or may not have noticed in the above 3 test sequences is that the Nikon 14-24mm @ 15mm images all display an increased ‘image magnification’.  This is due to excessive FOCUS BREATHING of this particular lens.  Focused at such a short distance – 12.5 inches – 15mm on the Nikon carries the same magnification you would associate with perhaps a 16mm or 17mm lens.

Lens Barrelling:

D4D0955 Lens Review   Irix Blackstone 15mm f2.4

Lens barrelling & angle of view of the Nikon 14-24mm f2.8 @ 15mm
12 feet and f14.

D4D0956 Lens Review   Irix Blackstone 15mm f2.4

Lens barrelling & angle of view of the Zeiss Distagon 15mm f.8 ZF2.
12 feet and f14.

D4D0957 Lens Review   Irix Blackstone 15mm f2.4

Lens barrelling & angle of view of the Irix Blackstone 15mm f2.4.
12 feet and f14.

The barrelling test loser is the Nikon – and you can also now see that, even at 12 feet, the focus breathing of the lens is resulting in a wider AoV – check the right edge of the air vent in the brick wall.

So the Nikon – at reasonable working distances – has a wider Angle of View (AoV) than the Zeiss, which in turn is marginally wider than the Irix.  I can’t say that I’m particularly bothered by this as the overall effect is minimal.

The Irix has slightly less barrel distortion than the Zeiss and so has to be the clear winner.

Coma Test

Seeing as the Irix originally piqued my interest as a super-wide prime with astro potential I’m really keen on looking at the coma it produces.

What’s Coma Andy and why does it matter to you?

First things first, here is what Coma looks like:

canon usm2 Lens Review   Irix Blackstone 15mm f2.4

Top Right corner Canon 16-35 USMII at 16mm & f2.8

The artifacts produced by Coma at wide apertures can make certain lenses redundant for astro photography – every single one of those upside down Cylon Warbirds is a star that’s supposed to look like a pin-prick of light.

Coma, or Comatic Aberration, is simply a distortion of off-axial point light sources.  The direction of the distortion can be sagittal (parallel to the lens diagonal), meridional (perpendicular to the lens diagonal), or a mix of both.

In the Canon lens above (that was over £1000 worth when new)  the coma is strongly meridional which is then pin-cushioned – terrible, and virtually impossible to correct for in Photoshop.  Yes, the coma vanishes at around f7/f8, but you can’t use those small apertures when shooting astro.

Contrast the image above to the one below from the Nikon 14-24:

nikon Lens Review   Irix Blackstone 15mm f2.4

Top Right corner Coma on the Nikon 14-24mm @ 14mm and f2.8

Okay, the Nikon sets the bench mark – the Coma is a fairly even mix of mild meridional and sagittal distortion which can easily be corrected in Photoshop where necessary.

Let me just say that the images above were shot under perfect dark sky conditions.  The image below by comparison is most definitely NOT – the sky is full of light pollution and we can’t see the stars at their full brightness, so the next shot is a slightly unfair comparative:

irix Lens Review   Irix Blackstone 15mm f2.4

Top Right corner Coma on the Irix 15mm @ f2.8

As I said, due to light pollution we can’t see any of the fainter stars, and the brighter ones look smaller.

And here is the Zeiss 15mm Distagon ZF2 under the same conditions as the Irix above:

zeiss Lens Review   Irix Blackstone 15mm f2.4

Top Right corner on the Zeiss 15mm f2.8 Distagon ZF2 @ f2.8

To be honest, the level of coma in both the Irix and the Zeiss are in no way unmanageable in Photoshop, and so are of little concern. Both are mild in their extremes of the image frame corners, the Zeiss being slightly biased towards sagittal and the Irix perhaps a tiny bit more meridional.

In both lenses the distortion ‘coma tails’ are smaller than the stars diameter and so a piece of cake to remove with a coma brush in Photoshop.

And if you want to know what a ‘coma brush’ is then go and buy my My Complete Guide to Photographing and Processing Night Sky Images.

Light Transmission

When I was doing the light polluted night sky shots I mentioned earlier I became very aware of something I hadn’t really noticed before – a T-stop difference between the Irix and the Zeiss:

Tstop 600x322 Lens Review   Irix Blackstone 15mm f2.4

Click the image to view larger

A 6 second exposure at the same aperture (f-number) and ISO on the Zeiss is roughly as bright as a 3 second exposure using the Irix.

The middle image is 3 seconds using the Zeiss, and is noticeably darker – I would say that the Irix transmits somewhere between +0.6 and +0.75Ev more light than the Zeiss – which let’s not forget is THREE TIMES THE PRICE!

 

So, what do I think of the Irix Blackstone 15mm f2.4 so far – bearing in mind that I need to test it for flare and focus breathing.  Well, I’m off to Norway for a week and hopefully I’ll get a few seascapes and high country midnight sun landscapes done in between the eagle action – and the Irix is the only superwide I’m packing!

I will conclude my review of this lens on my return from the land of the Vikings, but suffice to say, at the moment I consider possession of this lens a complete NO-BRAINER.

See my UPDATE on this lens HERE.

Monitors & Color Bit Depth

Monitors and Color Bit Depth – yawn, yawn – Andy’s being boring again!

Well, perhaps I am, but I know ‘stuff’ you don’t – and I’m telling YOU that you need to know it if you want to get the best out of your photography – so there!

Let me begin by saying that NOTHING monitor-related has any effect on your captured images.  But  EVERYTHING monitor-related DOES have an effect on the way you SEE your images, and therefore definitely has an effect on your image adjustments and post-processing.

So anything monitor-related can have either a positive or negative effect on your final image output.

Bit Depth

I’m going to begin with a somewhat disconnected analogy, but bare with me here.

We live in the ‘real and natural world’, and everything that we see around us is ANALOGUE.  Nature exists on a natural curve and is full of infinite variation. In the digital world though, everything has to be put in a box.

We’ll begin with two dogs – a Labrador and a Poodle.  In this instance both natural  and digital worlds can cope with the situation, because nature just regards them for what they are, and digital can put the Labrador in a box named ‘Labrador’ and the Poodle in a separate box just for Poodles.

Let’s now imagine for a fleeting second that Mr. Lab and Miss Poodle ‘get jiggy’ with the result of dog number 3 – a Labradoodle.  Nature just copes with the new dog because it sits on natures ‘doggy curve’ half way between Mum and Dad.

But digital is having a bloody hissy-fit in the corner because it can’t work out what damn box to put the new dog in.  The only way we can placate digital is to give it another box, one for 50% Labrador and 50% Poodle.

Now if our Labradoodle grows up a bit then starts dating and makes out with another Labrador then we end up with a fourth dog that is 75% Labrador and 25% Poodle.  Again, nature just takes all in her stride, but digital in now having a stroke because it’s got no box for that gene mix.

Every time we give digital a new box we have effectively given it a greater bit depth.

Now imagine this process of cross-breed gene dilution continues until the glorious day arrives when a puppy is born that is 99% Labrador and only 1% Poodle.  It’ll be obvious to you that by this time digital has a flaming warehouse full of boxes that can cope with just about any gene mix, but alas, the last time bit depth was increased was to accommodate 98% Lab 2% Poodle.

Digital is by now quite old and grumpy and just can’t be arsed anymore, so instead of filling in triplicate forms to request a bit depth upgrade it just lumps our new dog in the same classification box as the previous one.

So our new dog is put in the wrong box.

Digital hasn’t been slap-dash though and put the pup in any old box, oh no.  Digital has put the pup in the nearest suitable box – the box with the closest match to reality.

Please note that the above mentioned boxes are strictly metaphorical, and no puppies were harmed during the making of this analogy.

Digital images are made up of pixels, and a pixel can be thought of as a data point.  That single data point contains information about luminance and colour.  The precision of that information is determined by the bit depth of the data

Very little in our ‘real world’ has a surface that looks flat and uniform.  Even a supposedly flat, uniform white wall on a building has subtle variations and graduations of colour and brightness/luminance caused by the angular direction of light and its own surface texture. That’s nature for you in the analogy above.

We are all familiar with RGB values for white being 255,255,255 and black being 0,0,0, but those are only 8 bit values.

8 bit allows for 256 discrete levels of information (or gene mix classification boxes for our Labradoodles), and a scale from 0 to 255 contains 256 values – think about it for a second!

At all bit depth values black is always 0,0,0 but white is another matter entirely:

8 bit = 256 discrete values so image white is 255,255,255

10 bit = 1,024 discrete values so image white is 1023,1023,1023

12 bit = 4,096 discrete values so image white is 4095,4095,4095

14 bit = 16,384 discrete values so image white is 16383,16383,16383

15 bit = 32,768 discrete values so image white is 32767,32767,32767

16 bit = 65,536 discrete values so image white should be 65535,65535,65535 – but it isn’t – more later!

And just for giggles here are some higher bit depth potentials:

24 bit = 16,777,216 discrete values

28 bit = 268,435,456 discrete values

32 bit = 4,294,967,296 discrete values

So you can see a pattern here.  If we double the bit depth we square the value of the information, and if we halve the bit depth the information we are left with is the square root of what we started with.

And if we convert to a lower or smaller bit depth “digital has fewer boxes to put the different dogs in to, so Labradoodles of varying genetic make-ups end up in the same boxes.  They are no longer sorted in such a precise manner”.

The same applies to our images. Where we had two adjacent pixels of slightly differing value in 16 bit, those same two adjacent pixels can very easily become totally identical if we do an 8 bit conversion and so we lose fidelity of colour variation and hence definition.

This is why we should archive our processed images as 16 bit TIFFS instead of 8 bit JPEGs!

In an 8 bit image we have black 0,0,0 and white 255,255,255 and ONLY 254 available shades or tones to graduate from one to the other.

%name Monitors & Color Bit Depth

Whereas, in a 16 bit image black is 0,0,0 and white is 65535,65535,65535 with 65,534 intervening shades of grey to make the same black to white transition:

Gradient Monitors & Color Bit Depth

But we have to remember that whatever the bit depth value is, it applies to all 3 colour channels:

red Monitors & Color Bit Depth green Monitors & Color Bit Depth blue Monitors & Color Bit Depth

So a 16 bit image should contain a potential of 65536 values per colour channel.

How Many Colours?

So how many colours can our bit depth describe Andy?

Simple answer is to cube the bit depth value, so:

8 bit = 256x256x256 = 16,777,216 often quoted as 16.7 million colours.

10 bit = 1024x1024x1024 = 1,073,741,824 or 1.07 billion colours or EXACTLY 64x the value of 8 bit!

16 bit = 65536x65536x65536 = 281,474,976,710,656 colours. Or does it?

Confusion Reigns Supreme

Now here’s where folks get confused.

Photoshop does not WORK  in 16 bit, but in 15 bit + 1 level.  Don’t believe me? Go New Document, RGB, 16 bit and select white as the background colour.

Open up your info panel, stick your cursor anywhere in the image area and look at the 16 bit RGB read out and you will see a value of 32768 for all 3 colour channels – that’s 15 bit folks! Now double the 32768 value – yup, that’s right, you get 16 bit or 65,536!

Why does Photoshop do this?  Simple answer is ‘for speed’ – or so they say at Adobe!  There are numerous others reasons that you’ll find on various forums etc – signed and unsigned integers, mid-points, float-points etc – but really, do we care?

Things are what they are, and rumor has it that once you hit the save button on a 16 bit TIFF is does actually save out at 16 bit.

So how many potential colours in 16 bit Photoshop?  Dunno! But it’ll be somewhere between 35,184,372,088,832 and 281,474,976,710,656, and to be honest either value is plenty enough for me!

The second line of confusion usually comes from PC users under Windows, and the  Windows 24 bit High Color and 32 bit True Color that a lot of PC users mistakenly think mean something they SERIOUSLY DO NOT!

Windows 24 bit means 24 bit TOTAL – in short, 8 bits per channel, not 24!

Windows 32 bit True Color is something else again. Correctly known as 32 bit RGBA it contains 4 channels of 8 bits each; three 8 bit colour channels and an 8 bit Alpha channel used for transparency.

The same 32 bit RGBA colour (Mac call it ARGB) has been utilised on Mac OS for ever, but most Mac users never questioned it because it’s not quite so obvious in OSX as it is in Windows unless you look at the Graphics/Displays section of your System report, and who the Hell ever goes there apart from twats like me:

MacElCap8bit Monitors & Color Bit Depth

Above you can see the pixel depth being reported as 32 bit colour ARGB8888 – that’s Apple-speak for Windows 32 bit True Colour RGBA.  But like a lot of ‘things Mac’ the numbers give you the real information.  The channels are ordered Alpha, Red, Green, Blue and the four ‘8’s give you the bit depth of each pixel, or as Apple put it ‘pixel depth’.

However, in the latter part of 2015 Apple gave OSX 10.11 El Capitan a 10 bit colour capability, though hardly anyone knew including ‘yours truly’.  I never have understood why they kept it ‘on the down-low’ but there was no fan-fare that’s for sure.

MacElCap10bit Monitors & Color Bit Depth

Now you can see the pixel depth being reported as 30 bit ARGB2101010 – meaning that the transparency Alpha channel has been reduced from 8 bit to 2 bit and the freed-up 6 bits have been distributed evenly between the Red, Green and Blue colour channels.

Monitor Display

Your computer has a maximum display bit depth output capability that is defined by:

  • a. the operating system
  • b. the GPU fitted

Your system might well support 10 bit colour, but will only output 8 bit if the GPU is limited to 8 bit.

Likewise, you could be running a 10 bit GPU but if your OS only supports 8 bit, then 8 bit is all you will get out of the system (that’s if the OS will support the GPU in the first place).

Monitors have their own panel display bit depth, and panel bit depth costs money.

A lot of LCD panels on the market are only capable of displaying 8 bit, even if you run an OS and GPU that output 10 bit colour.

And then again certain monitors such as Eizo ColorEdge, NEC MultiSynch and the odd BenQ for example, are capable of displaying 10 bit colour from a 10 bit OS/GPU combo, but only if the monitor-to-system connection has 10 bit capability.  This basically means Display Port or HDMI connection.

As photographers we really should be looking to maximise our visual capabilities by viewing the maximum number of colour graduations captured by our cameras.  This means operating with the greatest available colour bit depth on a properly calibrated monitor.

Just to reiterate the fundamental difference between 8 bit and 10 bit monitor display pixel depth:

  • 8 bit = 256x256x256 = 16,777,216 often quoted as 16.7 million colours.
  • 10 bit = 1024x1024x1024 = 1,073,741,824 or 1.07 billion colours.

So 10 bit colour allows us to see exactly 64 times more colour on our display than 8 bit colour. (please note the word ‘see’).

It certainly does NOT add a whole new spectrum of colour to what we see; nor does it ‘add’ anything physical to our files.  It’s purely a ‘visual’ improvement that allows us to see MORE of what we ALREADY have.

I’ve made a pound or two from my images over the years and I’ve been happily using 8 bit colour right up until I bought my Eizo the other month, even though my system has been 10 bit capable since I upgraded the graphics card back in August last year.

The main reason for the upgrade with NOT 10 bit capability either, but for the 4Gb of ‘heavy lifting power’ for Photoshop.

But once I splashed the cash on a 10 bit display I of course made instant use of the systems 10 bit capability and all its benefits – of which there’s really only one!

The Benefits

The ability to see 64 times more colour means that I can see 64x more subtle variantions of the same colours I could see before.

With my wildlife images I find very little benefit if I’m honest, but with landscapes – especially sunset and twilight shots – it’s a different story.  Sunset and twighlight images have massive graduations of similar hues.  Quite often an 8 bit display will not be able to display every colour variant in a graduation and so will replace it with its nearest neighbor that it can display – (putting the 99% Lab pup in the 98% Lab box!).

This leads to a visual ‘banding’ on the display:

band Monitors & Color Bit Depth

The banding in the shot above is greatly exaggerated but you get the idea.

A 10 bit colour display also helps me to soft proof slightly faster for print too, and for the same reason.  I can now see much more subtle shifts in proofing when making the same tiny adjustments as I made when using 8 bit.  It doesn’t bring me to a different place, but it allows me to get there faster.

For me the switch to 10 bit colour hasn’t really improved my product, but it has increased my productivity.

If you can’t afford a 10 bit display then don’t stress as 8 bit ARGB has served me well for years!

But if you are still needing a new monitor display the PLEASE be careful what you are buying, as some displays are not even true 8 bit.

A good place to research your next monitor (if not taking the Eizo, NEC 10 bit route) is TFT Central

If you select the panel size you fancy and then look at the Colour Depth column you will see the bit depth values for the display.

You should also check the Tech column and only consider H-IPS panel tech.

Beware of 10 bit panels that are listed as 8 bit + FRC, and 8 bit panels listed as 6 bit + FRC.

FRC is the acronym for FRAME RATE CONTROL – also known as Temporal Dithering.  In very simple terms FRC involves making the pixels flash different colours at you at a frame rate faster than your eye can see.  Therefore you are fooled into seeing what is to all intents and purposes an out ‘n out lie.

It’s a tech that’s okay for gamers and watching movies, but certainly not for any form of colour management or photography workflow.

Do not entertain the idea of anything that isn’t an IPS, H-IPS or other IPS derivative.  IPS is the acronym for In Plane Switching technology.  This the the type of panel that doesn’t visually change if you move your head when looking at it!

So there we go, that’s been a bit of a ramble hasn’t it, but I hope now that you all understand bit depth and how it relates to a monitors display colour.  And let’s not forget that you are all up to speed on Labradoodles!