Camera Metering Modes
I always get asked about which camera metering mode I use, and to be honest, I think sometimes the folk doing the asking just can’t get their heads around my simplistic, and sometimes quite brutal answers!
“Andy, it’s got to be more complicated than that surely….otherwise why does the camera give me so many options…?”
Well, I always like to keep things really simple, mainly because I’m not the brightest diamond in the jewellery shop, and because I’m getting old and most often times my memory keeps buggering off on holiday without telling me!
But before I espouse on “metering the Uncle Andy way” let’s take a quick look at exactly how the usual metering options work and their effects on exposure.
The Metering Modes
- Average (a setting usually buried in the center-weighted menu)
- 3D Matrix (Nikon) or Evaluative (Canon)
You need to remember that metering is done via a separate sensor – not the IMAGE PLANE SENSOR (the contraption that records your images). This separate RGB sensor is usually of a CCD design and resides in the top of the camera viewfinder housing.
In the Canon 1DX this sensor has a pixel count of 100,000, and in the current crop of Nikon FX bodies it’s 91,000.
Average Metering Mode
When set in this metering mode all that basically happens is that your exposure value for the shot is determined by the average tonal brightness value of the entire scene that is projected onto the metering sensor.
It’s a tad old fashioned to say the least, but it’s marginally better than having no metering at all!
Spot Metering Mode (click images to open at full size in a new window)
This metering mode, together Nikon Matrix and Canon Evaluative, relies on a combined use of the of AF sensor points and the dedicated RGB CCD metering sensor.
In the first and third images below pay particular attention to the “contents” of the AF/metering bracket.
Within our AF/meter bracket in image 1 sits a galvanized metal post and two windows, both of which have white frames and one is full of sky reflection.
In the next image we’ve moved that center AF/meter bracket over to an area of the sky using the normal Dpad control on the back of the camera.
Now the exposure value has jumped by 3 stops from 1/500th sec to 1/4000th sec.
On image 1 we thought the highlights were possibly “blown out” in the sky – but seeing as we now know the sky is only an average 3 stops brighter than the street scenery, and we know our camera has a dynamic range of perhaps 9 stops or more, we perhaps have to question that initial assumption.
In image 3 below we’ve moved the AF/meter bracket over to the left to span a lighter and a darker wall, and a black downspout – no white window frames or reflections of the sky in window glass.
This has now given us and exposure of 1/400th sec…
…and we still have to ask ourselves if we have actually blown the sky.
Let’s just ping this shot over to Lightroom and see shall we..
But let’s just reduce the overall exposure and see if that detail is ACTUALLY on the sensor…
And can we make a good image inside Lightroom from this same RAW file that’s seemingly over exposed in the sky?
You bet ya we can:
And with another 2 minutes work I could make it look even better; but even as it is just check that histogram and the way I’ve redistributed the tones – luvly-jubbly midtones!
Buy my Training Videos, or book a training day with me if you want to KNOW how to do this – don’t expect me to give EVERYTHING away for free on my blog – I have to eat you know!
Anyway, we digress, so back to metering!
Spot metering DOES have a place in my armory of tactics – it really comes into it’s own in HIGH CONTRAST situations such as the one illustrated; but one does have to take GREAT CARE in where you take that spot meter reading from.
Having said that, I don’t deploy it quite so much anymore because of the simplicity of exposure bracketing and HDR/32 bit float imaging.
Center-Weighted Metering Mode
Center weighted metering is something I NEVER use; basically it’s a refinement of basic average.
Historically it was the second metering mode to appear on cameras “back in the day” and at that time it was brilliant – but things have moved on a bit since then, and in my opinion it has no place any more.
Because of how it works.
A circular area centered in the frame is metered – the exposure value given is the AVERAGE of what is covered by said circle.
On Nikon FX bodies for example this center circle can be 8mm,12mm,15mm & 20mm in diameter based on a sensor size of 36mm x 24mm
The simple FULL FRAME AVERAGE metering mode exposure value is also taken.
The two values are now averaged out with a bias of 75% to the center circle and 25% to the full frame average.
AND the center area is FIXED; it cannot be moved around the frame like spot or matrix/evaluative.
So all-in-all, the center weighted metering mode is archaic and about as much use as a hole in the head.
Spot would make an awful lot more sense…….if it wasn’t for the fact that the shot was done with my go-to metering mode – MATRIX (or Evaluative if I was a Canon shooter).
The Matrix or Evaluative Metering Mode
A common problem that people have when ‘doing photography’ is that they LOOK, but they do not SEE…
Think back to what I said about SPOT metering – you really DO have to concentrate hard and actually SEE what objects in the scene are under that single spot. This is hard to do especially with a wide angle lens as scene details are so small in the viewfinder.
They beauty of the spot metering mode is that it is:
- very precise
- moveable around the frame (given the area confines of the RGB metering sensor/AF array).
The one single redeeming feature of the Center-Weighted metering mode lies in the fact that it is variable in size.
Now imagine you had a metering mode that was centered on you key AF sensor, took on board the exposure values indicated, for example by the other 8 surrounding sensors if you are using a 9 point group as your auto focus mode; AND followed that AF sensor group around the frame as you basically compose the shot.
On top of that, what if the meter could also use lens data, and complex mixing algorithms based on scene recognition instead of the daft 75:25 mixing ratio of the center weighted metering mode?
Sounds good, and it’s called 3d Matrix metering by Nikon, and Evaluative by Canon.
Canon and Nikon use their own individual methods of obtaining this complex set of metering calculations, but at the end of the day they amount to one and the same thing – a really simple and effortless way for the camera operator to obtain a very good exposure.
Your Uncle Andy’s approach to metering is really simple – all my cameras are set to Matrix metering and they hardly ever move.
Like spot metering, the exposure value is calculated based on a point SPECIFIED by you, the operator.
But unlike spot metering, which is basically a ‘dumb’ reading, the matrix metering mode takes the opinion that what you are focused on is actually the bit of the frame that’s important – so that’s place it starts its exposure evaluation from.
Now matrix is not infallible, far from it – just try it in high contrast situations and you’ll soon see.
But with a little experience you begin to recognize scenarios and what they mean in terms of exposure value; this experience then leads you to take command of the exposure compensation adjustments on your camera.
Take these 3 images:
With this Kestrel we have bright sunny conditions – one of those potential high contrast scenarios I mentioned that can catch Matrix out if you are not careful.
Matrix exposure would have indicated 1/1200th sec shutter speed.
Under exposing by -1.0Ev on the compensation dial gives me 1 stop faster shutter speed AND protects those shiny highlights on the birds beak and very pale feathers on the face and wing edges.
I know it doesn’t look like it, but this upended swan close up is basically white on white, or low contrast situation – so I let the camera go with the Matrix exposure of 1/1000th and no compensation.
Another white on white situation then – OH NO IT ISN’T.
The swan was fine detail white-on-white an NOTHING else – the camera assumes that this commonest tone, white, is actually mid grey, and so exposes the whites as mid tones. The warm highlight under the wing is therefore protected from blowing due to the massive amount of headroom the highlights have on a linear capture.
If you are unsure of what I mean take a look at the top greyscale
You may also want to check back on the post about Gamma
So, to get back to “Miss Arctic Circle” above – I said that she is NOT a “white-on-white” or low contrast situation.
She’s got the hazel brown eyes, detail in that near black nose, and if she smiles a pinkish tongue and less than white teeth.
Matrix would have been indicating a shutter speed of either 1/1000th or 1/1200th, and at that level of exposure value the whites would have been exposed more as mid tones – and so those darker areas of the eyes, nose etc would have been considerably under exposed and either lost all their detail, or the detail would have to be exposure-boosted in post processing, which would have made those areas noisy.
Those darker areas represent a very small percentage of the total image field, perhaps about 4% at most, so spot metering them would have been fairly impossible with any degree of accuracy.
But going with Matrix and +1.3Ev dialed in on the exposure compensation control in effect, pushes the common tones up the linear gamma curve and exposes them as upper mid tones and low highlights – which is indeed what they are – and exposes the darker areas further up the gamma curve as lower mid tones – again, which is what they are.
With experience, riding the exposure compensation dial in conjunction with the matrix or evaluative metering modes becomes second-nature; your eye becomes accustomed to seeing the necessary corrections as you are shooting and moving around, and your fingers get accustomed to making the adjustments without the need to take your eye from the viewfinder.
So that’s how I look at the subject of metering modes – matrix and Ev compensation – Keeping It Simple.
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