I think you are the right track with lighting being an issue. Front and rear light conditions need to be just right. The actual scanner obviously controls the lighting very well, something you don't realise when using a phone/camera to capture the image. I have had a bit of success with GIMP now and will persevere. What I did was a bit hit and miss and I didn't write down the method.......... but the result was better than I expected.
Thanks for your help with this.
Rans6..............