• put your painting upright on an easel or flat surface with neutral background;
• remove any glass in front of the painting;
• put your camera on a tripod or a stable surface;
• make sure that the lens is parallel to the surface of the painting (If the canvas is straight, then put the camera straight too. If the canvas is inclined, tilt the camera.);
• preferably work with the timer to avoid vibrations;
• aim your camera at the center of the painting;
• make sure your painting is exposed to equally divided light (no direct sunlight, bright spotlights or other lamps that may cause hard shadows);
• make sure your camera is set to the highest resolution / best quality pictures;
• if possible, adjust the light balance to the weather and light conditions;
• work with a slow shutter speed if possible;
• don’t work (in the case of an SLR) with a wide-angle lens, but with a light telelens to prevent distortion;
• (for advanced users) take a measurement of the white balance on a white paper or even better a grey card.

Look here for an instructional video of Saatchi.online: www.youtube.com/watch?v=Vpj28da03JQ