Check that the document to be photographed is lightened uniformly, without shadows or shading offs (ideally lightened by 4 uniform sources at 45 degrees, facing the opposite corner and two times further than the device). A large neutral white or matt piece of paper can help you as a reflector to trim the light. Pay attention to the volumes of the surface : the rendering of the object depends on the direction of the light. The unique flash in the device is ’the worst lighting’ : too near to the object, in the direction of the camera...
The best is to fix your camera on a tripod. The movie plan is perfectly parallel to the artwork plan that will be photographed. The object is perfectly centered in the frame. These ideal conditions are hard to find and need a great attention to reflections, even more if the document is shiny.
Choose a lens
Try to avoid wide-angle lens - you will have distortion problems - except if you have up-market products or that distancing yourself from the artwork is impossible. If you can, use a fixed focal distance lens, about 50 mm and 24×36. For small objects that require a near shot, it is preferable to use a macro lens.
Distorsions and losses of acutance are more present on the borders of the lens. To dicrease this effect, you can take your photograph by framing slightly wider the object and choosing the highest definition possible.
The opening of the diaphragm has also its role to play in the quality of the image. Generally, you should avoid the widest and closest openings for middle openings that give better results with most lenses. You should only close more if you need a considerable depth of field as for example when photographing a sculpture.
Colors will look better if you cast off the white balance on a white piece of paper next to the object that will be photographed or on a neutral grey zone. You can obtain neutral grey thanks to a card that reflects uniformly all the bright radiations. It is also important to choose a good color light temperature if you take photographs digitally or if you use a balanced lighting for non-digital work.
Correcting distorsions with softwares
You can minimize the distorsions by distancing yourself from the object and by working with telephoto lenses and in particular optic ones. If you only have the camera’s flash as your unique lighting resource, you will need to shift perpendicularly to the painting to avoid reflections. Distorsions can be then modified even if some imperfections can still remain after using the software.
Ajust colors and contrasts
Before touching up, pay attention to the calibration, what you see in your screen won’t be necessarily what you will print or what you will see in another screen. You need to ajust the entire image production line to obtain a common impression when displaying on your screen.
Colors and contrasts adjustment of a digital camera, negative or slide scanning, is a delicate operation that you can do via softwares. That is during such operations that we appreciate colorimetric charters as generally we don’t have the painting in front of us anymore. The tool ’Color balance’ will correct the eventual predominant color. You should use cautiously the Lighting/Contrast tool of such softwares, that is to say only if the Level tool did not give satisfying results.