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.

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.

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).

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:

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!

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