I'll add a second for the tungsten film.

My wife was in grad school a few years ago and took two advanced degrees in painting. We took a lot of slides of both her work and other students'. Experimented with everything. One can make almost anything work, but using controlled lighting reduces some of the variables.

Whatever you use, beware of glare, shadows, and make sure everything (camera and artwork) is level and square. Crop in camera as much as possible, and mask the slides (there is tape made for just this purpose) for what can't be cropped in the 2:3 format.

Hanging the art on a flat black background helps, too.

Good luck.

David