Mike, whilst I agree that your philosophy is sensible, I think that there is a danger that one can get too hung up on the technicalities, the important target is to produce pictures that satisfy yourself, if they also please others, then maybe that should be considered a bonus, nothing more. I donít think pleasing others should necessarily be a prime objective for amateurs, that way leads to mediocrity. I see the images of too many people who are apparently hooked on the technicalities of photographic production, those who seem to have forgotten that the our prime objective is to produce an enjoyable picture. As you say altering only one variable at a time is a sensible, and, I think, scientific way to proceed, but it may be a bit dull!