Originally posted by Javaslinger So when you do the exposure compensation option.. what is it really doing?
It's not changing the aperture or shutter speed or ISO I don't thing... so what is it doing?
Or am I wrong? If it does change those, which is it changing?
EC is a way of "biasing" the meter. It's useful in P, Av and Tv modes (and perhaps elsewhere).
When you shoot in M mode, if you want to deliberately overexpose the shot - for example, so you can properly expose a subject that is backlit - you can SEE the amount of exposure, because in M, you can see the meter as a graph:
- . . .
: . | . +
The red colon there in the center is a technically balanced exposure, and the vertical bar shows how from from technically balanced the exposure will be with the current settings.
The problem is, in P, Av and Tv modes, you DO NOT get an exposure graph, at least not initially. Why not? Because in those modes, the camera - by definition - is always going to give you a technically balanced exposure. That's what those modes are for. You set one parameter, like aperture, and the camera figures the other (or others, if you're using auto-ISO as well).
So what do you do if you're shooting in P, Av or Tv mode, and you want to shoot a subject that's backlit? You bias the meter, that is, you dial in +1 EC or something like that.
Now the interesting thing is, while on an older camera like the *ist DS, the EC is shown in the Finder simply as a number ("-0.5", say), on a newer model like the K10D/K20D and I presume the K-7, when you use the +/- button to dial in some exposure compensation,
an exposure graph appears. The exposure indicator is now displayed where you want it to be - say, 1 stop to the right of center. But when you're in P, Av or Tv mode, the exposure indicator
stays put while you adjust the settings.
This is rather clever, I think. It means you can visualize what you're doing pretty much the same way whether you shoot in M or one of the other modes.
Will