Some lenses tend to distort, either pincushion or barrel. Primes do so much less than zooms, but good zoom tend to do it less, and often has at least some range that is largely free of such distortions. Wide angles especially tend to distort, unless they are very well corrected. I think you will have to look at SLR systems and find a lens that has minimal distortion. Don't worry too much about the camera, old 35mm bodies can be found used in great shape, the lens and a good stand will dictate the quality here.