WHY, HOW, & WHEN YOU NEED TO OVERRIDE
YOUR BUILT-IN EXPOSURE LIGHT METER
I am going to explain this in non-technical terms. Let's start with the problem, before I get into the solution. All cameras have a built-in exposure light meter, which measures reflected light, not the light falling on a subject--that's the problem. Why is it a problem? Let's think in terms of black and white for a moment. If we photograph a black or very dark subject, the meter will lighten it up to get it back to gray. If we photograph a white or very bright subject, the meter will darken it to get it back to gray. It will always try to bring the lighting, the exposure, to middle gray. Why? It was designed to give us the "correct" exposure, i.e., gray.
In color photography, "gray" would be mid-tones, between black or very dark and white or very bright. Instead of getting a white snowman, the meter, trying to give me the "correct" exposure, will give me a gray snowman.
Below is an in-the-field example of this problem. I was at White Sands, New Mexico recently. Before I go on, click on the link and notice how gray the white sand looks. Now, back to my story. When I was at White Sands, I made sure to take a couple of instructional photos for my classes and workshops. Before and After, if you will. Below is a photo of gray white sand. That is what the built-in exposure light meter gave me, which I knew it would. This is a field, real life, example of the problem.
Okay, so now we know about, understand, and see the problem. Before I share the in-camera solution, let me set the stage. I shoot on AV exposure mode, that is, aperture priority. Obviously, if someone shoots on manual exposure, the adjustments or solutions would also be done manually. Now, back to shooting on aperture priority. I am in total control of my desired depth-of-field, or f/stops, which is my style. In the above example, once I set the f/stop I needed to get the depth-of-field I wanted, the built-in exposure light meter gave me the corresponding shutter speed it thought I needed in order to give me the "correct" exposure. You've already seen the results of that.
The solution. Every camera has an exposure compensation dial on the camera body. It is a very tiny round or square button with a +/- in it. It is either on top of the camera or on the back of the camera. Rather than spend too many words explaining how it works, I'll let this gentleman explain it for you on this Youtube video. You might need to go to the index of your camera manual to find where it is.
If my subject, my photo, comes out too dark, like the White Sands example above, I need to move my exposure compensation scale toward the + side. Plus means more and more means more light. It sounds counterintuitive, but think of it this way. Below is a crude scale of bright-to-dark.
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Gray or mid-tone
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Black or dark
+2/3
+1
(I didn't want it so white that I would lose the details in the sand)












































