>>4235181If you have to leave them on the wall just get the highest resolution full frame camera with "pixel shift multi shoot" you can afford, with the sharpest lens longer than 50mm you can afford, and a tripod that gets the camera high enough to align the camera perfectly with the painting so all the lines are straight. Only shoot the paintings under high CRI light and at base ISO. Ambient lighting probably has a color cast so you want to turn that off - diffuse the light from high CRI LED panels or strobes to evenly light the painting (if the camera's pixel shift feature even works with flash).
It is very important that you use a sharp lens that does not have detectable vignetting or field curvature at its sharpest aperture, which is usually f5.6. This means you should avoid sony, because most lenses vignette a ton. Even a pentax K1 + pentax 100mm macro is better for document reproduction because the signal/noise ratio in the corners and edges is better, and it still has pixel shift. But you must buy the newest version of that lens, the older ones have extreme purple fringing issues.
You will want a way to hang a color calibration target in the frame, and use a color calibrated monitor while reviewing the files.
If you can take them off the wall there are copy stands and lighting setups made just for this.
If you can not afford full frame, the next best pixel shift feature is on micro four thirds, but you will have to use one that supports 16 shots for the noise reduction and consider stacking multiple pixel shift shots to create a noiseless image.
