2 Ideal camera settings
Keeping the ISO low will give you clean shots without an excess of grainy artifacts. ISO 100 to 200 is ideal. Each lens is different, but an aperture in the middle range (f8 or f11 typically) gives the sharpest results. Allow the camera to determine shutter speed by shooting in Aperture Priority mode.
Mount the camera on a tripod and disable any image stabilisation features. A portrait/telephoto lens will reduce glare and room reflections. Place a white card next to the painting for white balance. Use the two-second timer to prevent you shaking the camera when pressing the shutter.
Aperture closed too far will lose detail to diffraction
Aperture fully opened
Middle aperture setting
Easel If the lights cause flare, use a lens hood