Thank you very much Diana. I took a photo of one of my paintings (Cnicht in blue) outdoors yesterday and it did seem to make a difference. I had trouble lining up the view squarely, but after quite a few attempts, I got it almost right. I did have to crop the edges slightly though, as you say. I tend to paint on 16 x 12 paper, so I'm afraid the paintings won't fit into a scanner. I will look into The Gimp. I have never heard of that. Thanks for your advice. Much appreciated.

Try to photograph your paintings out of doors in natural daylight and directly from above without flash. You can then crop off any unwanted edges with a photo editing programme. The Gimp is a free, very good one you can download. Alternatively, have you tried scanning them? I know many of mine won't fit in a scanner so I always photograph then if necessary I use Image/ adjust/auto levels to make sure the colours and lighting are correct.