I have just spent last night in the darkroom experimenting with the 'Zone'System' of gauging the correct exposure when making enlagements. It is so DAMN EASY, I don't know why I have never done so before after all I have know about it for years. Out of 8 10x8 prints used as a experimental set, 7 were perfect and the 8th acceptable. I took the scale of exposure times out of a book by Gene Nocon, a Canadian ethnic native and a teacher in the photographic process. I cannot get over how easy it is once you have got your mind around it, because when first looked at it isn't clear cut. It works for colour as well as B&W. If you haven't tried it I recommend you do.