Metering Modes to Set Exposure in Digital Photography

Choosing a metering mode in digital photography is rumored to be difficult.  And I agree. You know what the hardest part for me is?  Figuring out which icon on the stupid camera goes with which metering mode!  So let’s get this part out of the way first:

Ok, so what do all these metering modes mean?   And how to they affect the pictures you take?  Here are the “official” definitions, and then some examples.

• Evaluative/Matrix – General purpose metering mode suited for portraits and even backlit subjects.  The camera sets the exposure automatically to suit the scene.  According to Nikon, “recommended in most situations.  Camera meters a wide area of the frame and sets exposure according to distribution of brightness, color, distance and composition for natural results.
• Partial Metering – Effective when the background is much brighter than the subject due to backlighting.  Partial metering covers about 9.4% of the viewfinder area at the center.
• Spot Metering - This is for metering a specific spot of the subject or scene.  The metering is weighted at the center covering about 2.3% of the viewfinder area.  For Canon, anyway.  I’m not sure what the Nikon % is.
• Center-weighted average - Weighted at the center and then averaged for the entire scene.  Nikon’s center-weighted metering assigns greatest weight to 8-mm circle in center of viewfinder and is the “classic meter for portraits.”

How to Meter on Digital Cameras

This part is pretty easy.  Aim the center of your camera at the spot where you want your exposure to be best.  Change your camera settings until your exposure meter tells you that you’re properly exposed, as I talked about a week or two ago.

How Metering Modes Affect Images

The following four images were taken in quick succession, on a tripod, with each of my camera’s 4 metering modes.  The recommended exposure is different for each shot. I measured my exposure at the center of the floral piece.  I then recomposed, to put the flowers slightly off center.

The first picture was taken with Canon’s evaluative metering mode, which is its attempt at reading the picture and determining the best exposure for the entire picture.  The large amount of highlights and backlighting cause this shot to be nearly the shortest exposure.  Some of the highlights are blown, but the subject is a bit underexposed.

In the next shot, the camera measured exposure essentially from 10% of the image right in the middle.  Because the center contains some of the bright sidewalk and maybe a bit of the backlighting, the subject is less exposed than is ideal.

This spot metering is the best exposure, to my taste.  The camera metered from 2.3% in the middle of the image, which was nothing but flower.  The flowers are exposed nicely, with good detail visible.  This exposure was the longest, because the subject is in the shadows and needed extra light.  Of course, for that reason, this is the image that has the most blown highlights as well.  But those blown highlights aren’t in important ares of the image.  I’m not so worried about them, especially since all my choices have some amount of blown highlights.

This center weighted average exposure is the worst.  It has the shortest exposure, and consequently the fewest blown highlights.  But the subject is too dark and drab.  The camera calculated this exposure because it measures a large part of the center.  It picked up lots of the highlights on the sidewalk and the top of the picture and determined that the exposure should be short.

Which Metering Mode to Use?

My camera is usually set to Evaluative.  However, if I’m shooting a brightly backlit subject like the flowers above, I sometimes change the metering mode to Spot.  If I know the light won’t change much, I keep the mode on Evaluative and get close enough to my subject that it entirely fills my lens.  I read my meter and then back up to my shooting location. Scooting up close to the sujbect on Evaluative ensures that no distracting highlights or shadows affect your meter reading and is about the same as Spot Metering.

Spot is almost essential, however, outside on a day when exposure changes frequently, like days that are partly cloudy and windy when the clouds blow across the sun frequently and quickly.

Ok, that’s my take on metering.  It took me forever to write this post because I had trouble finding a day with the proper backlighting to show the differences between the modes.  I enjoyed it and learned a lot!  Hope it’s been helpful your you as well.

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