Tag Archives: Exposure Compensation

Expose well

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Your camera wants everything to be grey. So every time you shoot a very light subject, such as snow, the camera will make it look too dark. And when you shoot a dark subject, like this coat, it will look too bright:

This is because your light meter labours under the engineering assumption that what you point it at is neither bright nor dark. When that is not the case, that assumption no longer holds and you need to adjust the value your meter comes up with.

So in the case of the dark coat, you turn down exposure (use “exposure compensation”, the +/- button) by 1-2 stops and now you get this:

Solved!

What is Exposure Compensation actually “doing”?

Just the same that your camera always does, except more so or less so. So of your meter is setting aperture, then exp comp means it is set to a slightly lower or higher aperture value than it would other wise have done. If your meter is setting shutter speed, ditto for shutter speed. If you are in “P” mode, your camera can set either or both.

Snow

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I have a reminder for you of how to expose for snow.

Snow and sand (yes, beaches to a camera look just like snowscapes) are brighter than your average scene.

So to get them to look natural, i.e. to get them to look bright, you need to tell the camera it is looking at a bright scene.

Unless you do this, the scene will look dark.  The camera, by virtue of its reflective light meter technology, tries to make everything look mid-grey (we call this “18% grey”). Like this:

Not bad. But unless you want the dark look for effect, it’s not good either; it was brighter than that outside my second home, the other day.

With +1 stop exposure compensation (that’s the plus/minus button), it looks like this:

And that is better. Your guideline:

  1. Snow should look white, not grey.
  2. The histogram should have a peak (the snow) on the very right, just before the end of the graph.

So use Exposure Compensation, have fun, and dress warmly.

Or if your thing is a beach, don’t dress at all.

Exposure compensation for drama

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…is the most important control after focus, if you use your camaera’s semi-automatic modes.

What does it do? It makes the picture darker and light.er But how? Does it change the pixels? Adjust the ISO? Change aperture? Do processing in the chip? What?

Actually it is very simple.

You use exposure compensation (the +/- button on your camera) only in modes where the camera is already adjusting something.

If you are in aperture mode (A/Av), the camera constantly adjusts the shutter speed to match the light. If you are in shutter speed mode (S/Tv), the camera adjusts the aperture. In Program mode (P), the camera adjusts either/both.

All you are saying with +/1 is “I want you to do that as usual, but to do it slightly differently to how you’d normally set it. + means do what you do but make it brighter than you’d normally do; – means do what you do but make it darker than you’d normally do (like in the picture below).

MVWS7002

So in Av/A mode, it adjusts the time as usual but to a slightly different value. In Tv/S mode, ditto for the aperture. In P mode, either.

No magic, then.

Exposing snow – etc.

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Say you are taking a picture of your child skiing down a slope. A student asked me this the other day.

So I produced a kid on a hill and shot that:

MVWS9188

OK, it was a white piece of paper with a scribble looking not very much like a skier. But still. The camera thinks my white sheet is gray (that’s the assumption built into reflective light meters) and produces a gray picture. The histogram will be “in the middle”.

If you now use “exposure compensation” (the +/- button) and turn it up to +2, you get something that looks much more like it:

MVWS9189

And if the bump in the histogram is not yet close to the right edge, you can go even higher.. like +2  3/4:

MVWS9190

And more and we bump against the right edge and lose detail, so we stop there.

Next time you shoot your kid skiing down a hill, and it’s all white, remember that. “Your picture looks grey unless you tell the camera otherwise”.