[DaveB]

I've had some success using the 90mm APO for photographing large pastel drawings. Even under mixed lighting I can usually get a color balance that is very close to the original.

Despite the distance afforded by the 90mm lens the plane of focus will change across a 1m wide drawing. To compensate for the plane of focus and to minimize the slight parallax distortion I will often make a composite using 4-6 separate shots that I stitch in CS3 or something similar. The trick with that technique to take care to maintain camera and tripod strictly orthogonal to the surface of the artwork being photographed.

With a smaller piece of artwork I probably would be comfortable getting in closer with a lens I was confident in, say the 50mm.