Sorry this isn't a clearcut question.
I've been setting up to shoot artwork. I'm using the AV setting on my cannon which allows me to set a higher aperture (5.6) and set the ISO (100). The problem I'm worried about is the automatic exposure with artwork subjects that are of different brightness.
The camera, (on tripod) automatically exposes long enough to capture the image. But for a brighter images with lighter colors won't the exposure take less time, and for darker images won't it take more ? (I think this was happening in my first experimental shots, but it could have been other variables). The results seem OK but I want to make sure.
I want to use an automatically exposure if I can. With the higher aperture and low ISO, even with studio lighting, an exposure can take a while. But I also want all the images to be consistent, and not have the darker ones over exposed.
And I also don't want to set different settings every time I photograph an image.
Should I maybe use a test pattern, or neutral gray to estimate the exposure length, then set the exposure manually for all the images no matter how light or dark they are?
Or perhaps does the camera automatically know there really are just darker colors and will provide a consistent image no matter the subject?
Or further should I just worry about this during the RAW image processing. (I read somewhere that RAW captures images at a different gamma level than your eyes naturally see).
NOTE, I'm using a Canon T2i, shooting RAW, with a 35mm Macro lens on a sturdy tripod, using the EOS utility to operate the camera from the computer. I have a decent softbox light setup at 45 degree angles, though I may have to sometimes adjust them depending on the finish sheen and texture of the paintings. The experimental shots I've done using the automatic exposure seem pretty good so far. I just want to make sure I get a consistent shot for all the images.