Exploring Metering Modes - Digital Photography School

Exploring Metering Modes

This is the third in a series of four articles about exposure by Andrew S Gibson – author of Understanding Exposure: Perfect Exposure on your EOS camera. You can read the first lesson, which explored the reasons for using program, aperture priority and shutter priority modes, and the second lesson, which explained why your camera’s meter gets exposure wrong.

01.jpg

In my last article I looked at the fundamental reason why your camera’s meter sometimes gets exposure wrong. Camera meters measure reflected light, and will give an incorrect exposure reading if the subject is lighter or darker than average (you can read the article again for a full recap).

But there’s another reason why your camera’s meter may get the exposure wrong – and it’s to do with the metering modes that your camera has. Most cameras have several exposure modes (my Canon camera has four). Each exposure mode is designed with for a different purpose, and works a specific way. If you are struggling with exposure, it may be because you don’t fully understand the way the metering mode that you are using works.

Most digital SLRs have the following exposure modes:

Centre-Weighted Metering

02.jpg

This mode weights exposure towards the centre of the viewfinder, as per the diagram above.

Centre-weighted metering works well if your subject is in the centre of the frame. If not, you have to point the centre of the viewfinder at your subject, hold the shutter button half-way down to lock in the exposure, then reframe.

Centre-weighted metering has been around a long time – if you own an old film camera it may be the only metering mode that it has. It’s predictable and easy to use once you understand that the camera is metering from the centre of the viewfinder.

Spot Metering

03.jpg

The camera takes an exposure reading from a circle in the centre of your viewfinder. The diagram above shows the spot metering circle in the viewfinder of the EOS 5D Mark II.

Spot metering takes practise. Remember in the last lesson we learnt that cameras measure reflected light, and that the camera is expecting the tones within the area that it meters to average out to mid-grey? If you point the spot metering circle at a tone that is lighter or darker than mid-grey, the camera will give you an incorrect exposure reading.

One way to use the camera’s spot meter is to point it at something in the scene that is mid-grey in tone. Grass is a good example, and one approach to metering is to simply use the spot meter and take a reading off any grass or greenery in the scene.

Another technique is to use an 18% grey card (you can buy these from photo retailers). I’ve seen these used by portrait photographers. They ask the subject to hold the card up, take a reading from the card, then put it away, set the camera to manual mode and use those settings. They only need to re-meter if the light changes.

Another situation where spot metering comes in handy is when you have a bright subject against a dark background. This can happen during a theatre performance or a concert. You can take a reading from the subject and the camera will ignore the background.

Partial metering

04.jpg

Works just like spot metering but with a larger circle. Like spot metering, it works well for metering brightly lit subjects against dark backgrounds. You can use partial metering for taking a reading from a larger part of the subject than the spot meter.

Evaluative Metering

05.jpg

Note: Evaluative metering is Canon’s term and the one that I’ll use in this article. Nikon uses matrix metering and Pentax and Sony use multi-segment metering.

Centre-weighted, spot and partial metering all take an exposure reading from the centre of the frame. Given that most photographers prefer to place the main subject off-centre for compositional reasons, this means that taking an exposure reading with one of these modes is not always the easiest way to work.

Evaluative metering was developed by the camera manufacturers to make it easier to measure exposure with off-centre subjects. The camera divides the viewfinder up into zones and compares exposure readings from each zone to come up with a suggested exposure setting. The above diagram shows the way the viewfinder is divided up into 63 zones on some EOS cameras.

The camera weights the exposure reading towards the active autofocus point (or points) as they are likely to be covering the main subject. It takes into account the readings from nearby zones and analyses the contrast of the scene to come up with an exposure setting.

Each camera manufacturer uses a slightly different process in their evaluative metering modes. While the manufacturers don’t release precise details of how their cameras calculate exposure in evaluative metering mode, there will be a guide in the instruction manual. It’s well worth a read so you understand how it works on your camera.

My preferred way of working is to use evaluative metering, take a photo, look at the histogram and then adjust the exposure if necessary. For me, this is the simplest way of arriving at the optimum exposure. However, everybody works differently and once you understand how the other metering modes on your camera work you may find one of the others is best for you.

Exposure Compensation

Now that you understand more about your camera’s exposure modes, and why they may get the exposure wrong, you need to know what to do when the exposure is incorrect.

If you are using an automatic exposure mode, the easiest way is to use your camera’s exposure compensation function.

06.jpg

If you’re unsure how to set exposure compensation then check your camera’s manual – each camera is different. On mine, I just turn the Quick Control dial (circled above) on the back of the camera with my thumb. I like this way of working because I can dial in exposure compensation while looking through the viewfinder.

If the photo is underexposed, use exposure compensation to increase the exposure by a stop or two. Then check the histogram to see if the exposure is correct (if you’re unsure how to read the histogram, then read this excellent article).

If the photo is overexposed, you can use exposure compensation to reduce the exposure.

07.jpg

The amount of exposure compensation applied should be displayed in the viewfinder. Again, check your manual. On my Canon cameras the display looks something like the diagrams above. The top display shows zero exposure compensation, the middle display shows +1 stop exposure compensation and the bottom display -1 stop exposure compensation.

The next lesson is the last in the series. I’ll take a look at manual mode, show you how to use it and, more importantly, explain why you should use it.

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Andrew S. Gibson is a writer and photographer living in New Zealand. He is the author of over twenty photography ebooks and he's giving two of them away. Sign up to his monthly newsletter to receive complementary copies of The Creative Image and Use Lightroom Better.

  • http://blogs.gonomad.com/traveltalesfromindia/ Mridula

    I should run and explore what options I have. Thanks for explaining it so clearly. And in the meanwhile I took some pictures at the Everest Base Camp trek.

    http://blogs.gonomad.com/traveltalesfromindia/2012/05/and-i-am-back-from-the-everest-base-camp-trek.html

  • http://photos.rickscheibner.net Rick

    There are different approaches to this. If I need to adjust metering one way or another, I’ll go to manual mode and bump the shutter time up or down. For my purposes, it’s critical to keep aperture constant. Moving that by a full stop at a time can have drastic effects on my work. If adjusting shutter speed doesn’t get me where I need to be, I’ll hit the ISO. Rarely the aperture, though, at least for metering purposes.

  • http://www.kerstenbeck.com Erik Kerstenbeck

    Hi

    Sometimes metering can be tricky, especially when there just is not a lot of time to mess around due to other factors. I always shoot RAW and if need be I bracket – this way I am virtually assured to get something useable…like in this shot of wine glasses shot at an event which I was covering….had to rush off to do “The Real Work”

    http://kerstenbeckphotoart.wordpress.com/2012/05/26/a-glass-menagerie/

  • http://www.robmelanson.com Robert

    Try comparing your camera’s meter to an external meter. I was quite surprised by the difference, now I always use an external meter for important shots.

  • Juan

    Hello Andrew.

    I think the picture for Spot Metering is wrong. If I’m not wrong, Canon states that its spot metering system measures light in approximately 4% of the scene, which would be down to the little square inside the circle. On the other hand, when I used evaluative I didn’t get as good results as I wanted so I changed to spot and started reading about using it: for portraits point the center of the frame at the cheeks or even at a white shirt; outdoors, point at green subjects (not so dark, though pointing at any green has worked for me most times); always locking the exposure and recomposing for what you desire. I have had better results since I use spot. I hadn’t really tried partial and did try a little center-weighted but the results were not as satisfactory as with spot. I have also found that, in addition to it being more reliable when exposing, spot also lets me get faster shutter speeds when shooting portraits (specially indoors) and pointing at the subjects’ cheeks. Thanks for posting, specially about this tricky subject that can really impact our photography.

  • http://www.chrisgin.com Chris Gin

    Nice article! One thing I found with my Canon 7D was that Evaluative metering behaved very differently than my 40D. In fact it seemed almost like Spot metering and was causing me all sorts of problems. I switched to Centre-Weighted Metering and it’s more like what I’m used to.

    Also I found the metering in LiveView different on the 7D. It seems to again be like Spot metering based on where the little square on the LCD is positioned, so as you move the square around (which I do to check focus in various places) the metering changes!

  • http://canondigitalcameras.co.za Martin

    Hi Juan,

    You are right, I also have the same problem, my picures were also not clear and i am still reading a lot in our forum abot the right settings and it looks to me that people understand it differently.

  • Adam

    I think the following statement in the article is incorrect (happy to be corrected if I am wrong about this!):

    “Centre-weighted metering works well if your subject is in the centre of the frame. If not, you have to point the centre of the viewfinder at your subject, hold the shutter button half-way down to lock in the exposure, then reframe.”

    Certainly on my Canon 60D holding the shutted button half-way only locks the focus not the exposure, the camera will keep meter reading up to the point you take the shot. To lock the exposure you need to use the exposure lock feature, the AE button on my 60D, this locks the exposure for a predetermined amount of time (can be set in the menu).

  • Tom K.

    I use a Nikon D7000; while selecting an AF point with spot metering, the camera uses the same spot for metering and focusing. I find this combination the most useful because if I want to focus on it, its also probably where the light is most important for my shot.

  • http://www.andrewsgibson.com/blog Andrew S Gibson

    Thanks for your feedback guys.

    Juan – Yes, about 4% depending on the camera. Looks about right to me, that’s about 1/25th of the viewfinder area.

    Chris – that’s interesting, first time I’ve heard someone say that. I wonder if they did change the formula for the 7D?

    Metering in Live View is different. The camera meters from the sensor and always uses evaluative metering. That’s because the exposure sensor is located in the pentaprism and so no light reaches it when the mirror is flipped up.

    Love your photos by the way!

    Adam – The default is that the shutter button locks in exposure when you press it half-way and keeps it there until you either release the shutter button or take a photo. Alternatively you can use the AE button, as it sounds like you’re doing.

    If the half-press on the shutter button isn’t locking in the exposure, you may have changed the function in the Customs Function menu. Check out Custom Function IV-1 in your camera’s instruction manual.

    Hope that’s clear!

    Tom – thanks for that, seems like Nikons work differently from Canons in this respect. Sounds like a good idea.

  • Aperture Ray

    One of the clearest informative, in-depth and well written article i’ve ever read on this site. (With key word being in-depth… both staff and guest writers take note!)

    Can’t wait for part two of this article. Great job!

  • Mike

    I have to say that as someone that does this for a living, this is the one area that I still haven’t “masteeed” this helps, but I’ll still mess it up!

  • Jeff

    “Centre-weighted metering works well if your subject is in the centre of the frame. If not, you have to point the centre of the viewfinder at your subject, hold the shutter button half-way down to lock in the exposure, then reframe.”

    This doesn’t work well for shots taken with a wide open aperture because your subject won’t be in focus when you reframe. Any tips on how to get the right exposure for non-centered subjects when shallow DOF is needed to get the shot you’re looking for?

    http://flic.kr/p/9WNixt

  • Justin

    I have played with all the various metering modes over the 30+ years I’ve been shooting, and while I still use them all from time to time, 90% of my shooting I now do with spot metering. I find that I’m able to zero in on the exposure I want pretty quickly by aiming at the area of greatest interest, adjusting until I see what I want, and shooting. With tools like “focus lock”, “exposure lock” and “move aiming point”, I get all the control I need with very little experimenting.

  • Robinhj

    I used to use spot metering a lot more when I used my old film Olympus OM-4 because it allowed you to take multiple readings. This meant if you you had two separate subjects against a dark or light background you could get an averaged exposure to match both or maybe take two readings on one and three on the other (up to 9 in total) to bias it one way. It also had a separate button to measure for black or white rather than grey exposure so you could expose for white snow or black shadow. Do any digitals have that functionality?

  • Robinhj

    Jeff, your question seems to assume that holding down the button half-way will lock both exposure *and* focus. Most cameras have an option in the menus to choose if that is the behaviour you want. If you don’t have that option then take a reading as suggested in the article then use manual or exposure compensation to get that same reading when not pointing at your subject.

  • Roberto

    A bit of a newbie question: I use a Nikon, but I suppose this would apply to Canons as well: when in single point focus mode and using spot metering, does the spot vary with the focus point chosen?

  • http://www.facebook.com/profile.php?id=100003406141123 Myrrh

    I’ve got to tell you, I SO appreciate this enirte series!a0 I was referred to your blog from a photography facebook group when I had several questions about backlit photos, and I have not been disappointed!a0 In fact, I share you with all of my friends!a0 I am exactly where you described yourself as having been:a0 a natural light photographer who is a bit afraid of venturing into flash.a0 My new 430exII should arrive in the mail today and because of you, I AM SO EXCITED!a0 Thank you for your generous spirit!

  • KB

    I appreciate this, but maybe it’s just my brain, I am not understanding how you can meter for exposure and then choose a different focus point. I believe I have been metering on whatever I want to be in focus. Is that not right? What am I doing wrong? Should these be two separate steps I should be doing?

  • http://www.andrewsgibson.com/blog/ Andrew S. Gibson

    It depends. Metering from whatever the camera is focused on will work if the subject is not too light or too dark. But if it is you have to step in and override the camera’s settings. Exposure compensation is the easiest way if you are using the camera in any of the automatic modes.

  • Ron Art Allado

    I also have the same sentiments. I used to think that wherever I point my focus on and press the shutter halfway to lock the focus, if I do not release the shutter as I tilt the angle of view, the exposure will not change from which I initially focused on (given that single point metering and focus is used). It’s kinda difficult to practice using that AE/lock button (the one that locks exposure when remained pressed or until it is pressed again depending on its settings. Some top photographers in their video courses claims that they are still practicing, for years, using the AE/lock button in candid moments).

Some older comments

  • Myrrh

    June 17, 2012 02:10 pm

    I've got to tell you, I SO appreciate this enirte series!a0 I was referred to your blog from a photography facebook group when I had several questions about backlit photos, and I have not been disappointed!a0 In fact, I share you with all of my friends!a0 I am exactly where you described yourself as having been:a0 a natural light photographer who is a bit afraid of venturing into flash.a0 My new 430exII should arrive in the mail today and because of you, I AM SO EXCITED!a0 Thank you for your generous spirit!

  • Roberto

    June 3, 2012 03:53 am

    A bit of a newbie question: I use a Nikon, but I suppose this would apply to Canons as well: when in single point focus mode and using spot metering, does the spot vary with the focus point chosen?

  • Robinhj

    June 2, 2012 04:57 pm

    Jeff, your question seems to assume that holding down the button half-way will lock both exposure *and* focus. Most cameras have an option in the menus to choose if that is the behaviour you want. If you don't have that option then take a reading as suggested in the article then use manual or exposure compensation to get that same reading when not pointing at your subject.

  • Robinhj

    June 2, 2012 04:51 pm

    I used to use spot metering a lot more when I used my old film Olympus OM-4 because it allowed you to take multiple readings. This meant if you you had two separate subjects against a dark or light background you could get an averaged exposure to match both or maybe take two readings on one and three on the other (up to 9 in total) to bias it one way. It also had a separate button to measure for black or white rather than grey exposure so you could expose for white snow or black shadow. Do any digitals have that functionality?

  • Justin

    June 1, 2012 09:25 am

    I have played with all the various metering modes over the 30+ years I've been shooting, and while I still use them all from time to time, 90% of my shooting I now do with spot metering. I find that I'm able to zero in on the exposure I want pretty quickly by aiming at the area of greatest interest, adjusting until I see what I want, and shooting. With tools like "focus lock", "exposure lock" and "move aiming point", I get all the control I need with very little experimenting.

  • Jeff

    May 31, 2012 12:31 pm

    "Centre-weighted metering works well if your subject is in the centre of the frame. If not, you have to point the centre of the viewfinder at your subject, hold the shutter button half-way down to lock in the exposure, then reframe."

    This doesn't work well for shots taken with a wide open aperture because your subject won't be in focus when you reframe. Any tips on how to get the right exposure for non-centered subjects when shallow DOF is needed to get the shot you're looking for?

    http://flic.kr/p/9WNixt

  • Mike

    May 29, 2012 11:52 pm

    I have to say that as someone that does this for a living, this is the one area that I still haven't "masteeed" this helps, but I'll still mess it up!

  • Aperture Ray

    May 29, 2012 10:57 pm

    One of the clearest informative, in-depth and well written article i've ever read on this site. (With key word being in-depth... both staff and guest writers take note!)

    Can't wait for part two of this article. Great job!

  • Andrew S Gibson

    May 29, 2012 04:30 pm

    Thanks for your feedback guys.

    Juan – Yes, about 4% depending on the camera. Looks about right to me, that's about 1/25th of the viewfinder area.

    Chris – that's interesting, first time I've heard someone say that. I wonder if they did change the formula for the 7D?

    Metering in Live View is different. The camera meters from the sensor and always uses evaluative metering. That's because the exposure sensor is located in the pentaprism and so no light reaches it when the mirror is flipped up.

    Love your photos by the way!

    Adam – The default is that the shutter button locks in exposure when you press it half-way and keeps it there until you either release the shutter button or take a photo. Alternatively you can use the AE button, as it sounds like you're doing.

    If the half-press on the shutter button isn't locking in the exposure, you may have changed the function in the Customs Function menu. Check out Custom Function IV-1 in your camera's instruction manual.

    Hope that's clear!

    Tom – thanks for that, seems like Nikons work differently from Canons in this respect. Sounds like a good idea.

  • Tom K.

    May 29, 2012 11:31 am

    I use a Nikon D7000; while selecting an AF point with spot metering, the camera uses the same spot for metering and focusing. I find this combination the most useful because if I want to focus on it, its also probably where the light is most important for my shot.

  • Adam

    May 29, 2012 09:00 am

    I think the following statement in the article is incorrect (happy to be corrected if I am wrong about this!):

    "Centre-weighted metering works well if your subject is in the centre of the frame. If not, you have to point the centre of the viewfinder at your subject, hold the shutter button half-way down to lock in the exposure, then reframe."

    Certainly on my Canon 60D holding the shutted button half-way only locks the focus not the exposure, the camera will keep meter reading up to the point you take the shot. To lock the exposure you need to use the exposure lock feature, the AE button on my 60D, this locks the exposure for a predetermined amount of time (can be set in the menu).

  • Martin

    May 29, 2012 07:38 am

    Hi Juan,

    You are right, I also have the same problem, my picures were also not clear and i am still reading a lot in our forum abot the right settings and it looks to me that people understand it differently.

  • Chris Gin

    May 29, 2012 06:32 am

    Nice article! One thing I found with my Canon 7D was that Evaluative metering behaved very differently than my 40D. In fact it seemed almost like Spot metering and was causing me all sorts of problems. I switched to Centre-Weighted Metering and it's more like what I'm used to.

    Also I found the metering in LiveView different on the 7D. It seems to again be like Spot metering based on where the little square on the LCD is positioned, so as you move the square around (which I do to check focus in various places) the metering changes!

  • Juan

    May 29, 2012 06:10 am

    Hello Andrew.

    I think the picture for Spot Metering is wrong. If I'm not wrong, Canon states that its spot metering system measures light in approximately 4% of the scene, which would be down to the little square inside the circle. On the other hand, when I used evaluative I didn't get as good results as I wanted so I changed to spot and started reading about using it: for portraits point the center of the frame at the cheeks or even at a white shirt; outdoors, point at green subjects (not so dark, though pointing at any green has worked for me most times); always locking the exposure and recomposing for what you desire. I have had better results since I use spot. I hadn't really tried partial and did try a little center-weighted but the results were not as satisfactory as with spot. I have also found that, in addition to it being more reliable when exposing, spot also lets me get faster shutter speeds when shooting portraits (specially indoors) and pointing at the subjects' cheeks. Thanks for posting, specially about this tricky subject that can really impact our photography.

  • Robert

    May 29, 2012 03:12 am

    Try comparing your camera's meter to an external meter. I was quite surprised by the difference, now I always use an external meter for important shots.

  • Erik Kerstenbeck

    May 29, 2012 02:56 am

    Hi

    Sometimes metering can be tricky, especially when there just is not a lot of time to mess around due to other factors. I always shoot RAW and if need be I bracket - this way I am virtually assured to get something useable...like in this shot of wine glasses shot at an event which I was covering....had to rush off to do "The Real Work"

    http://kerstenbeckphotoart.wordpress.com/2012/05/26/a-glass-menagerie/

  • Rick

    May 29, 2012 02:31 am

    There are different approaches to this. If I need to adjust metering one way or another, I'll go to manual mode and bump the shutter time up or down. For my purposes, it's critical to keep aperture constant. Moving that by a full stop at a time can have drastic effects on my work. If adjusting shutter speed doesn't get me where I need to be, I'll hit the ISO. Rarely the aperture, though, at least for metering purposes.

  • Mridula

    May 29, 2012 01:06 am

    I should run and explore what options I have. Thanks for explaining it so clearly. And in the meanwhile I took some pictures at the Everest Base Camp trek.

    http://blogs.gonomad.com/traveltalesfromindia/2012/05/and-i-am-back-from-the-everest-base-camp-trek.html

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