Photographing Flat Artwork
Framed artwork or other flat, shiny objects can can create serious problems with reflections. For that, the cure is to make sure your photographic lights only reflect away from the camera.
With your artwork flat on a table, the floor or a wall, you line up the camera so it is aimed exactly perpendicular to the surface of the piece. Then, you place one photo light on each side of the artwork, aimed at approximately a 45-degree angle to the surface. That way, any light striking the glass surface will bounce right back toward the other light, instead of at the camera.
Here is one such setup...
Here, I'm using an actual photographic copy stand with the camera supported on a central pole and two clamp lights aimed from either side. You could make the same sort of arrangement, with the camera on a tripod and the artwork on the floor or shooting horizontally on a wall.
The main thing is to keep the lights from shining on the camera and from reflecting back toward it. All other lights in the room should be off.
I took a shot of that artwork with the camera on full automatic exposure and got this result...
Because of the lighting arrangement, there aren't any serious reflections, but the matte board was a light gray, which came out sort of yellowish. That's because I didn't set the camera's white balance control and, on full auto, it got things wrong.
For my next try, I preset the camera's white balance control to tungsten, to match the type of lights I was using and got this result...
And that's pretty close to how that print looks hanging on a wall.
If you want to read more about setting white balance control and how to get accurate exposures, check my Guide Cameras, Controls & Settings.
I would have liked slightly more even lighting in the photograph above, but in this case, I had placed the lights close to the artwork, so they would show up in the setup shot I posted above. In practice, you'd want to keep the lights far enough away to avoid any potential hot spots.