Place the artwork in the shade, outside, preferably on an overcast day. I like to put the artwork on a chair, so I don t have to do so much bending. It is important that the artwork is squared up in the view finder. If it is skewed, the image will also be skewed. Because the camera format is different than the painting size, including a border of space around the painting includes the full image size.
Nothing is cut off.
I can crop the full image in photoshop. If it looks like your varnish is shiny in the camera, it will also appear in the photo. Change the direction of the painting. I find that shooting under the eaves of the house where it is in the shade is the best. Do not shoot artwork that is under glass.