I have tried to take photos of them, but never satisfactorily. Nowdays I always scan them in. If the drawing is larger than the A4 area of my scanner I scan each section then stitch them together in Photoshop. PS has a feature which automatically places the sections together in exactly the right place. I always overlap the sections then tidy up each layer before flattening the whole image. I convert to grayscale and usually use the equalise command to enhance the contrast, then I play with the levels (Black, mid tone and white) before saving as a jpeg. Hope all this helps.