Hello all. I'm here sporadically these days since I'm painting pretty much full time. I regret not helping painters more, especially here on this page.
Photographing paintings is especially difficult because of the glare. Because of this, I've researched all over for better techniques. I've found a way to do this with cross-polarization. I bought a 20 dollar linear polarized film https://www.amazon.com/gp/product/B06XWXRB75/ref=oh_aui_detailpage_o05_s01?ie=UTF8&psc=1
from amazon and also a polarized lens for my camera lens (14.00). Obviously, you'll need a camera, a light source and also a tripod for the camera. I'm currently using a 5000K fluorescent bulb in a Ikea floor lamp. I taped the film onto the lamp. I made sure all my other light sources were blacked out or turned off.
Situate the camera so that it is full frontal to the canva but out of view. You can fill the frame if you wish. I use a neutral gray card to balance out my white balance later. I put my white balance on my camera to 5000k. Turn the lens until the glare is gone.I do use a slow shutter speed and a remote since it's pretty dim. Then I do the rest of the editing in lightroom. I do have an example of the before an after. Those of you that follow me on instagram have already seen it.
When I took photos before, I would put my lights at a severe angle, almost directly above it and then I'd put the painting in the lower part of the view finder. This did help reduce glare, but it made the light off balance from the top to the bottom. After doing cross-polarization, I realized it still lost some color and contrast in the glared areas even though I couldn't actually see the glare. That is the second example below. The first example is the same exact set up for both shots, just the lens turned (not polarizing).
I hope this helps some of you get better photos of your paintings.