10/26/2012

Metering: Part 2, Metering Modes

We have looked at how your camera uses it's internal light meter to decide the correct exposure, so now let's turn our attention to the various metering modes available, and how these affect how your camera meters for exposure.

Below is the common metering modes - I've listed both Canon and Nikon's metering terms (or at least what I think Nikons are - I don't have one!) if you have a different camera model I'm afraid you may need to check your camera manual. The shaded areas in the photograph are meant to represent the area that each mode considers.

Evaluative (Canon) / Matrix Metering (Nikon)
This will be the default setting on most cameras. It basically takes all the pixels present in the entire scene tries to even them out to reach middle gray. Although it sounds like it wouldn't work well, you will actually find that quite a lot of scenes average out to meet this middle gray, and therefore your camera will get it right on a lot of occasions! It's basically a good all-rounder, but it's particularly useful for landscape photography when you want everything in the scene to have equal consideration. However, it's a bit like Auto for metering - its making a decision based on an average scene and this may not be the best one for the image you are trying to shoot. 





Centre-Weighted (Canon & Nikon)
In this modes, the camera gives more weight to the tones in the centre of the image although it will also take some information from the outer meter points.  It's probably easier to predict how the camera will react using this mode (rather than evaluative) so a lot of people will use this as their "standard" metering mode. It's quite useful in a lot of scenes so again an all rounder but with a bit more predictability. Please note that if your subject is not in the centre of the frame, you would need to measure exposure with the subject in the centre, enter your settings, then recompose.



Spot (Canon and Nikon)
This mode tells the camera to meter from a very small specific area of the scene (around 2.5% of the frame)  Therefore instead of judging exposure based on the entire scene, it just focuses it's metering on a very small spot - in portrait photography this is likely to be the cheek.  This helps the camera by pinpointing exactly the area that you want the camera to expose for.  This gives you the most control over the exposure of your image by far, but it is more difficult to use (at least to begin with). One reason to use this mode is with images that are backlit, so that you are exposing for the subject and not the bright background.  I's also very helpful for metering off something that you know will come close to middle grey - either your  Gray Card or something in the scene.

I believe this works slightly differently between Canon and Nikon, and with different models within each range. For example with my Canon you can only meter with the central focus point,  so you need to meter, set/lock exposure, then recompose. However, I believe that with some Nikons and higher spec Canons you can spot meter with your outer focus points too, but please check your camera manual to get the right information.




Partial (Canon)
Canon cameras have an additional option of Partial - it's just a slightly bigger area than spot, and works in pretty much the same way. 

Which one should I use???
I know some of you might ask this question and the fact is there is no one right answer to this! It all depends of what you are shooting,  the lighting of the scene, and your subject in relation to the light.  I know photographers that just use Evaluative all the time, and adjust using exposure compensation. Others use  centre weighted as their "go to" mode because the results are more predictable. Others swear by using Spot metering all the time so they have complete control over the exposure.  For me, I tend to have my camera on Evaluative most, as it's just easier to use when you are trying to focus on a three year old jumping up and down and running about the place - using spot metering in that situation is just a recipe for insanity.  I know I can probably make the adjustments needed in Lightroom or Photoshop if I have to (I'm no purist!) however, if the subject is backlit, or I'm photographing an adult or co-operative child (or mine asleep!) then I would move to Spot Metering and try to get it right in camera - either by photographing off the cheek or using my gray card. 

There is a little bit more to discuss about metering and that is Exposure Compensation - which can be used with any of the mode above. It probably requires a bit more explanation than I have time to go into today so I'll cover it in (yet another!) follow-up post!  

Meanwhile have a look and check out your metering modes and have a great weekend. 



7 comments:

Jan said...

wonderful explanation. i like how you greyed out the metering modes for us "visual learners!" here's a random question, if you're metering with spot meter, do you find that your meter will go hog wild up and down when shooting? will the meter be more consistent with the evaluative/matrix mode on? it drives me crazy when my meter goes up and down so quickly so i'm wondering if the mode has something to do with that.

Audrey said...

Yep, if you use spot you are metering for such a small area that when you shift your meter will go off. For example, if you had metered off the skin, but then moved so you can focus on the eye, the meter reading will change but it will still meter correctly for the skin (assuming you have compensated if need be) providing the light doesn't change don't worry about it moving. If using evaluative, it will change too but not as wildly as it is taking in the whole scene which will have a wider range of tones. Hope ths helped!

Jan said...

i'm rereading your post after my class just confused me. i'm suddenly not confused after your post! love your explanations!

to double check my understanding...

1. set metering mode (matrix/evaluative)
2. meter off of subject's cheek or something grey (so that meter reads 0)
3. take picture
4. look at picture. if under/overexposed, make adjustments with exposure compensation.
5. take picture and decide if that fixed exposure
6. if fixed, continue to take pictures and ignore if the meter goes up and down and all around as long as the light remains consistent.

do i have that right?

Audrey said...

That's pretty much it! If using evaluative you would need to fill the screen with your grey card, or switch to spot metering to meter off a subject's cheek or a grey card. If you know already that you will need to over/under expose from what your meter is telling you just adjust by shooting one stop over or under (or whatever you need) You can look at the test picture you have taken and see what adjustments need to be made but it can be difficult on your veiwfinder, the best way is to read your histogram, if you know how to do that. Meter will move around but don't worry about it! x

Anonymous said...

I tried taking some photos of my daughters little plastic horse on top of three books that were on the window ledge with a white blind behind them. If I spot metered off the little brown horse it would still be underexposed, if I spot metered off any one of the books the books and horse were properly exposed. One book was yellow, one white and one was black. Is this because the 'spot' the camera uses is bigger than the little horse so it still takes into account the bright white blind? By the way I didn't really want a picture of the horse, I was just practising while my daughter was asleep ... but you probably guessed that!

Anonymous said...

I should have added that the room was dark except the light coming through the blind, I.e the subject (the horse) was backlit.

Audrey said...

Very tricky to answer without seeing the set-up! I'm going to assume that the camera is seeing the light in the background. When going for back-lit I always manually dial in a plus compensation. Back lighting is definitely a more tricky lighting situation, best to do as you did but make sure you dial in more exposure. I don't know if that helps too much!

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