Originally Posted by
jcuknz
The question of image quality ... I have not done any tests but simply assumed that it comes from the quality of the CU lens and personally I remain content with a 2 dioptre since greater powered lenses do seem to lack IQ, particularly around the edges. The lens needs to be more than single element and in this situation I have a LF camera lens giving me about 7 dioptre and with its multi element construction gives good IQ. So while the cheap amazon [et al] sets get one started I think you need to go to Raynox or other multi-element lenses if one intends to do a lot of this work, and Raynox costs not that much more, though from the one I saw it is rather small and wouldn't work on a large DSLR lens. If the CU lens is smaller than the camera lens one looses light transmission as if one had added another iris up front.