There has been much written about the use of supplementary lenses - specifically, "Proxars" with Hasselblad lenses. Some is truth, much is not. IMHO, the best "filter" to determine which is which, is to apply the Laws of Optical Phenomena. Let me respond to some arguments. I don't know of a way to import various "pieces" included in other messages, so I will be typing with ten ham-handed fingers, and I apologize for any inaccuracies in transcription. "max_ebb" Yes, you did. Is there another set of Optical Laws that applies to other lens systems? I only know of one set - can you direct me to others? I take this as an insult. If it is not, please quote the specific statement I made to make this "apparent" to you. I was AGREEING with your statement that additional glass attenuates more light. That agreement was to you, "Not understanding"? Q.G. Of course not. That was only meant as a single illustration where one auxilliary/ supplemental lens DOES... and I'm glad that you agree that the possibility does exist. No. I have never said there was *no* deteriation effect, or that there was... only that both Proxars AND Extension tubes allow the application of the lens outside of the original design parameters. Whether the effect either has is unacceptable or not is up to the user/ photographer. As fine as the Zeiss/ Hasselblad lenses are, they were not designed to "be the best they could be". Their design was limited by the design parameters, one of which was cost. They are GOOD - damned GOOD - but by no means "perfect". The "best they could be" would have exceeded - by a bunch - cost limits. "Cheap, crappy" .... For the moment I'll leave "crappy" alone. "Cheap"? You have GOT to be kidding... Now - am I mistaken, or were the designers of the Proxars - or at least those who decided their applicablity to the Hasselbad System - the same people who designed the lenses? Or are you suggesting some sort of sabotage from an outside group? Crappy? I would suggest that the idea "simple=crappy" is not NECESSARILY (let me repeat: NOT NECESSARILY) a carved-in-stone ultimate truth. Most. if not all, of the FINEST camera lenses are composed of finely crafted SINGLE elements, some cemented together. Now, please refrain from telling me "what I think". You simply DO NOT KNOW what I think. Using that as a tool of intimidation/ domination will not work.