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"Vision without execution is hallucination."


Thomas Edison

Monday, March 15, 2010

Meter for Details on the Shadow Side

In my last post I talked about metering bright desert sun from the frontlit direct sun side of a subject, but it's just as important to know how to meter accurately if you get brave and explore the shadow side of a subject. The problem with a lot of subjects that are backlighted is that the area behind the subject (the sky, the sea, snowy mountains) are often far brighter than the subject and more often than not the meter gets fooled by the bright areas. One way to handle this is to simply move closer to your subject so that the shadowed areas dominate the frame, giving less chance for the highlighted or bright areas to trick the meter.  You can then use your meter lock feature (pressing the shutter release button halfway down and holding it will lock the exposure), but the problem is that most meter-lock features also lock focus (especially on simpler cameras). What this means is that if you move close and take a reading and lock it, you're also locking focus from that position. If you move back to take a wider scene, oops, the shot is out of focus. You can also zoom in for a closer reading, but if you're using a variable-speed zoom (which most zooms are--meaning the effective aperture changes as you zoom) then this will mess up the exposure, too.

The best solution, if your camera has it, is to put the camera in the manual exposure mode.   In manual mode the camera will give you some type of viewfinder indication of the correct reading and once set, it will retain those settings until you change them. Then you can walk right up to your subject, meter until you get a good reading for the shadow side, and since the camera won't change the settings, you can shoot from anywhere with that reading--and, of course, refocus as often as you like.

If you don't have a manual mode, look and see if you camera allows auto-exposure bracketing. Using this feature you can shoot three (or more) frames in a row and alter the exposure for each frame by a specified amount--say, one full stop. When you press the shutter the camera shoots one frame at the meter reading and then one frame at one stop underexposed and another at one stop overexposed, etc. Your manual will explain the bracketing options (you do know where your manual is, don't you?). I often bracket even when I'm shooting manually just to cover myself--which is exactly what I did in taking this shot of the San Xavier Mission south of Tucson.

Keep in mind, however, that very often back-lit scenes have an extremely broad dynamic range (the range of dark to light areas) and sometimes the contrast is simply beyond the camera's ability to hold both shadow and highlight areas--so you have to sacrifice one or the other. But again, as with frontlit scenes, if you check your histogram after you've made a test frame, you can see if you're losing shadow or highlight detail.

Learning to meter in all kinds of situations will vastly improve your percentage of "keepers" and will save you tons of work in editing.

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