View Full Version : Could someone explain the various metering modes.

18-01-2012, 10:07pm
I'm a little unsure of how to use the various metering modes, or more to the point, WHEN to use which of the metering modes - Evaluative, partial, spot, centre weighted average. I can kind of guess that spot is that the camera takes the light metering from that spot, and I'm guessing the center weighted average must give extra weight to an average of the metering around about the centre, but that's really only based on word meaning. I'd kind of like to know a bit more about how it all works so as to know which to use and when.

18-01-2012, 10:30pm
You have the basic premise right. All the metering does is give you a reference for exposing the resulting subject mid-gray.
The various modes just takes different parts of the scene to make that decision.
Spot, as you correctly assumed takes the reading from a small spot, usually in the middle but on some cameras it can be tied to the AF point you use.
Evaluative is the opposite, it takes the reading from the whole scene.
Partial and centre weighted are somewhere in between.
Centre weighted also evaluates the whole scene but gives more weight to the subject in the centre.
I think partial is just a larger area spot metering.

There's no hard and fast rule about which to use when.
For me:
Eg. I often spot meter a person's face if I don't care much for the background. I'd then use exposure compensation based on how light or dark I want the face to appear eg. around +2/3EV for fair Caucasian skin type.
Evaluative for a general scene without any main subjects. Again using exposure compensation to change the exposure bias.
Centre weighted eg. Shooting a scene with something in the foreground such as people as much subject.
That's just a rough guide. Use whatever works and you'll develop what works best for you.

18-01-2012, 10:36pm
Evaluative evaluates the entire image to determine exposure settings. Probably the most used mode and good for landscape style photography.
Partial or Centre weighted only evaluates a small portion of the image (usually the centre but some cameras allow you to change the location). I would think this mode is better for portrait where you want correct exposure on someone's face but watch out for over exposing your backgrounds.
Spot only evaluates a very small section of the image. I use this mode with exposure lock when I'm having difficulty in getting the correct exposure with the other two modes.

Each mode has its uses, the fun part is going out and trying each of them to see what works for you.

heh.. swifty beat me to the post, swifty is right about partial/center weighted where it does evaluate the entire image. Its algorithms give higher priority to the centre/partial in this mode.

18-01-2012, 10:45pm
Thanks for that Swifty.
I decided to do a search online for the user manual, and see what it says there. It pretty much says the same, but doesn't really explain when to use each of the modes. Your examples above are quite helpful. I appreciate the effort you put into such a thorough reply.

I'm mostly asking because so many of my photo trips turn out to be overcast days, and then heaps of the photos end up with the sky blown out badly, so I'm assuming that the camera is metering off a darker part of the scene. I'm trying to work out how to best overcome that, or at least be aware of how and why it's doing what it does, so I can compensate for it, or use the best mode, for future photos.

It's a new problem for me, because for some reason it very rarely happened with photos on the old P&S Fuji Finepix - even if the sky overexposed, it was rarely badly so, and usually recoverable - whereas blown out skies have destroyed a HEAP of photos that I've taken with the 60D, so I really need to learn how to adjust to compensate, or I'm going to get really frustrated really fast.

18-01-2012, 10:55pm
Thanks for that filpee. Landscape is what I do the most of. Yet I'm pretty sure I mostly use spot, which is probably the worst option for landscape. Learning by taking multiple shots using each mode is the ideal, but unfortunately, a lot of my "learning" time is on actual trips where I kind of need the shot to work and can't always take multiple versions, so learning some of the best settings in here before trips is the next best thing when I don't get much experimental time.

Funny. Going and getting the manual off the net turned out to really help clarify the different Focus modes as well - AI focus, AI Servo, and One Shot - I hadn't realised that AI focus will switch between the other two modes automatically. I'd been doing the switching between One Shot, and Servo, as I needed to. Yet could probably have left it in AI and left it to do the changing if the subject moved.
It's funny, I thought I already had - RTFM - but with a camera this "fancy" I guess I should have RTFM multiple multiple times. There's just too much to retain it all with one read.
Thanks heaps for the replies, now to go make sure that my day off tomorrow becomes some experimenting time, and my bedtime reading tonight is another run through the manual just in case there are other areas I've still not really grasped (AE lock being one of them).

So much to learn, and so little time. Retirement is still 25 years away. It could take most of that ;)

18-01-2012, 10:56pm
No worries, Ezookiel.

Evaluative: also called "matrix" in Nikonland. (I don't know what they call it in Pentaxville, but they are bound to have it.) The smartest of all metering modes. Essentially, the camera electronic system looks at everything, considers light in different parts of the frame, focus distance, location of the AF point selection, last week's Tattslotto numbers, you name it. It adds them all up, tries to figure out what you are doing, and decides on a best-guess exposure according to some very complex and secret set of black magic rules programmed into it at the factory. It is reasonable to assume that Canon spend a lot of time and effort on this, and probably a bit of time quietly trying to figure out how well Pentax and Nikon are doing at the same job and whether there is anything in the other-brand systems they should look at copying. (Naturally, the reverse applies as well.) Evaluative focus is generally the most reliable AF mode if you are just going to leave everything up to the camera and hope for the best. On the other hand, it is by far the most difficult mode to predict, so if you are actively managing your exposure, adding exposure compensation where appropriate and depending on your purpose and case-by-case judgement, evaluative exposure mode tends to lead to trouble. You don't understand how it works (no-one does outside the factory), so it is very difficult to second-guess. Summary: best mode for point and giggle, probably the worst mode for proactive photographers.

Centre weighted average:: exactly what you expect. Averages the entire frame, but pays extra attention to the centre and less to the outsides. A pretty simple bit of maths, so simple that old pre-electronic meters could do it. Good because it is simple enough to understand and (mostly) guess first time - i.e., you can usually look at a scene and think "hmmm ... I reckon the exposure system will pay a bit too much attention to the bright sky here, I'll dial in some +ve EC" and get it fairly right first time. (With evaluative you never quite know what it's going to do!) On the other hand, it doesn't cope as well with unusual exposure situations as evaluative, so unless you are alert it's easier to get blown highlights or other mistakes. Summary: a good general-purpose mode for most photographers.

Spot: just what it says. Meters only a small spot in the centre of the frame. Can be wildly wrong if you just point and hope! But that's not how you use it: with spot metering, you must chose what object you want to meter off, and do it every single time you shoot. If the object isn't in the centre of the frame, you have to meter and recompose. Advantage: you should get correct exposure every time, limited only by your ability to select appropriate metering points. Disadvantage: tedious, gives terrible results if you don't do it properly. Summary: very effective but not for everyone.

Partial: essentially a cross between spot and CWA - it meters a spot, but it's quite a large spot, often large enough to be fairly representative of the whole scene. For some strange reason, Nikon and Pentax (so far as I know) don't offer this mode, it's a Canon-only one. I like partial best of all. I hated it to begin with - the old 20D didn't have the spot mode I was used to - but soon came to regard it as the best compromise of all: sensitive enough to somewhat off-centre objects to often need no exposure compensation, but mostly taking in the primary subject in the centre, and above all, simple - simple enough to let you glance through the viewfinder and regularly guess how much EC you will need.

I used to use partial all the time, but these days, although I still never use anything but partial for bird work, I tend to use evaluative or CWA for landscapes and general photography.

I think there was a poll here as few years ago about exposure modes. From memory, Evaluative/matrix was the most popular, with spot #2, but I may be wrong. Might be interesting to run it again, actually.

18-01-2012, 11:04pm
Wow. Thanks Tannin. That's a really really comprehensive answer. Very very helpful!!

18-01-2012, 11:18pm
Hmmm ... you have to be quick! I started off typing the first reply!

Excellent answers from Swifty, though a little vague on the differences between partial and CWA (which is fair enough, he's a Nikon uyser so it's not relevant to him).

Which mode should you use?

Well, you could go around selecting different modes for different situations, but as a relatively inexperienced photographer, you might find that you are just getting confused and failing to master any of them, or at least taking a longer time to learn exposure than you should.

My suggestion is to pick one and stick to it. You might start using other modes later on - indeed I encourage you to - but pick one mode and use it for everything until you have learned how to expose most things correctly the first time (well, most of the time, anyway). At that point, you can start exploring the other modes - though you will probably tend to come back to Old Familiar anytyime that you are in doubt.

Which one? Hmmm .... I reckon evaluative is too hard because although it is the smartest, it is smart and you never know what it's going to do next. Let's work an example:

You have a moderately dark scene with a few very bright highlights, which are quite small and not in the centre of the frame. In this particular case, you don't care if you blow them a little, the main subject is most important. If you use evaluative, will it take those highlights into account and under-expose? (If so, you need some +ive EC.) Or will it ignore them, in which case the darkish main subject will lead to a slight overexposure so you need a little -ive EC! Who knows? You can only shoot and chimp, adjust and shoot again.

Now consider the same scene with spot metering: you can simply meter off the main subject, allow a half stop under because it's darkish and you want it to look like that, and then either set a manual exposure or dial in EC 'till you are happy. With CWA or partial, it's still nice and simple (especially so with partial), so you can probably guess the right amount of EC straight off.

On the other hand, partial tends to be a bit tricky for landscapes as you tend to get mostly sky or mostly land in the central spot (which is still quite small compared to the whole frame) and moving the frame up or down a little bit can give you wildly different exposure values (just like spot). CWA is less prone to this and, all things considered, might be your best choice. But please yourself - any of the four modes can be used, it's just a matter of learning the particular habits of whichever one you prefer.

18-01-2012, 11:53pm
No probs.

Spot can be very useful in landscapes but takes more time and some maths in your head. You can spot meter a number of different areas in your composition, do a mental sum for the brightest and darkest areas and decide on the actual exposure yourself. Too much work for me.
In digital it's easier to use matrix or centre-weighted, take the shot and evaluate your histogram/image. Retake if necessary.
You run into trouble with spot when there's a tremendous amount of dynamic range in your scene and you haven't spot metered enough areas to base your exposure judgement on.
I suspect you may have done this with your blown skies.
You have a beautiful scene, overcast but very bright skies. You spot meter the ground/tree/building etc rendering them nicely exposed but blow the skies.
If you used evaluative, what you're likely to end up is an underexposed foreground but fairly well exposed skies as the sky's brightness often overwhelms the rest of the scene. In digital, especially at base ISO, this is often a better scenario since its easier to boost shadows in post.
You can also increase EV compensation until the highlight just starts to blow. Tip: Turn your highlight blinkies on. This ensures you maximize the amount of captured data without going over the threshold where detail can no longer be recovered. Google the term ETTR.
But as Tannin alluded to evaluative metering is sometimes unpredictable. Unfortunately it's very complex and too smart for its own good sometimes. Did you see that the latest Canon pro body 1Dx has some 100000 sensors for evaluating the scene now!!!

19-01-2012, 12:04pm
Thanks for that filpee. Landscape is what I do the most of. Yet I'm pretty sure I mostly use spot, which is probably the worst option for landscape.......

I'm also a Nikon user, but spot is the best mode to use for landscaping.

My point as a Nikon user is relevant tho, as Swifty said: some cameras spot metering is set to use only the central point of the viewfinder image, whereas other cameras(most Nikon's that I know of) link the spot meter to the AF point selected.
This is also important in choosing the camera(body) as some (Nikon)cameras have only 3 or 5 AF points, and others have 39 or 51 points. And to add to this the Dx(APS-C) cameras have a wider coverage are in the viewfinder for their AF/Meter points compared to Fx(full frame) cameras.
D300 is a great camera to use in that it has 51 points to focus and (spot)meter from and a wider coverage across the frame to boot when compared to a full frame camera.

I do 'manual evaluative' metering where I flick from spot to spot to take readings of various points and then decide which part of the scene I'm willing to compromise or recover, or whether a filter of some type is appropriate. That's why I use spot metering.
If you camera is of the type that only does spot metering from the central portion of the frame, then it's probably not the right mode to use efficiently.
Of course you still can, as I used to with the D70s, but with that camera, I used to handhold it, and physically scan the scene with the camera before I set it up on the tripod. (the D70s has only 5 AF/meter points).
With the D300, 99% of situations I just mount the camera to the tripod and scan the scene by moving the AF point around to get my readings.

For any Nikon users reading this, while Tony is right in that we don't have a 'partial' mode, what we get is the ability to adjust the size of the centre weighted metering area.
Each level of model will have different options, where the lower specced/earlier model cameras will have fewer options to the higher end/modern cameras have more options.

20-01-2012, 8:51am
Now the light dawns as to what AE Lock is for.
The problem I've had is when the area that I want to meter off, is different to the area I want to focus on.
I'm guessing that is when you meter off the area you want to meter from, and then use AE Lock so you can take the photo using a different area for the focus.
LOL. Now it makes sense. I was using AE Lock only when I was taking a string of shots to be joined together for a pano.
Shame when your camera is smarter than you are. It's only taken me 3 or 4 months for the penny to drop.

20-01-2012, 8:57am
I have moved this from the Gear Talk (Canon) forum to the NTP forum, cause I reckon the questions and answers in this thread are something more newbies could learn from. Thanks everyone for your input above.

20-01-2012, 9:20am
There are several items and diagrams in the NTP book...

BTW :plogo: Multi-segmented, Center-weighted, and Spot Metering

20-01-2012, 10:24pm
Thanks for this.

I had it backwards. Was metering on the ground then shooting sky :Doh:

I have now realized that it's best to meter at the brightest area(if large) and let the lower ground fall to slight shadow...ESP sky

Please correct me if I am still misguided.....

For a portrait type meter behind so the subject get exposed and doesn't fall to shadow.?

Also just figured out that shutter speed is referred to sometimes as exposure time - that helped put it into perspective too

20-01-2012, 10:31pm
@kerrie ... and if you shoot raw it is much easier to bring up the dark, than recover blown light areas!
In fact recovery of blown highlights is nigh on impossible

William W
23-01-2012, 6:43am
Partial & Spot Metering

Within the Canon range, size of the Partial Area metered changes between camera models.
The CHANGE seems NOT to make the centre bias consistent, between different format sensor sizes.

If one uses Partial Metering often, this feature is important to note when using two or more cameras or when changing the camera one uses.

The same is also so applicable for for Spot Metering Bias (the area the spot reads).

I use a Canon multi camera kit and I don't obsess with the numbers, but I do use both these metering modes: and I know how "big or small the target is" and the different size it is when using different cameras.
For example, how the metering target relates to a usual known subject at a given distance – i.e. how much area the meter will read, of adult person, standing at a Full Length Shot.