Dan was talking about lenses without focal points, and I said that I knew of no such thing. I was kind of waiting for someone to point out that the focal point of some telephoto lenses is between the front lens element and the subject. So, I guess you changed the topic, since I never said anything about exit pupils, only that laser lenses are different than the ones we use, since they DO use light in parallel rays. John _____ De: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] En nombre de flyback1 Enviado el: Wednesday, June 20, 2007 5:10 PM Para: opendtv@xxxxxxxxxxxxx Asunto: [opendtv] Re: Red camera lenses Don't know where you got the idea that some camera lenses have no focal point. All I pointed out is that in telecentric lenses, the primary light rays leave the exit pupil in parallel lines. That is the idea conveyed in both of these sites. Cliff Benham johnwillkie wrote: Bad guess. I visited both sites, scanned both pages. I saw, on BOTH, a lens diagram with a focal point, and what appeared to be an image that was upside down from the source. What subtle issue did I miss with these instrumentation cameras? How macro-focusing desires all too easily lead to "bug's eye" lenses? John Willkie _____ De: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] En nombre de flyback1 Enviado el: Wednesday, June 20, 2007 12:42 PM Para: opendtv@xxxxxxxxxxxxx Asunto: [opendtv] Re: Red camera lenses johnwillkie wrote: Thee are lenses without focal points? John Willkie _____ De: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] En nombre de flyback1 Enviado el: Saturday, June 16, 2007 12:52 PM Para: opendtv@xxxxxxxxxxxxx Asunto: [opendtv] Re: Red camera lenses Read about Telecentric lenses: http://www.lhup.edu/~dsimanek/3d/telecent.htm <http://www.lhup.edu/%7Edsimanek/3d/telecent.htm> http://www.computeroptics.com/telecentric.html I guess you didn't bother to open and read from either URL...