Here's how I shoot my paintings. This may sound rather involved, but if you have the equipment, it works beautifully. I photograph with studio strobe lights wich give me accurate daylight color balance and give out a nice strong light. I polarize both the lights and the camera. I have attached a low tech overhead view illustration of my set-up. On the next post I will attach photos of an unfinished painting showing with and without polarization.
1. Set up your camera on a tripod so that the lens is as high as the center of the canvas and square with the canvas.
2. Set up lights so they are as high as the center of the canvas and aimed at the canvas at less than a 45% angle.
3. Keep lights back far enough so that the canvas receives even illumination.
4. Place a sheet each of polarizing material over both lights. See photo of light with polarizing material hanging in front of it. Make sure the sheets are hanging in the same direction (polarizing the light the same way). I bought my sheets of polarizers online at B&H Photo in NY.
http://www.bhphotovideo.com/c/produc...0_Filter_.html
5. Check with a light meter that illumination of canvas is even corner to corner. Use the incident setting on your light meter. That is, the setting that measures the light that is falling on the canvas