Archived posting to the Leica Users Group, 2001/02/28
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]John Collier wrote: I have been reading the LHSA archives and came across a curious statement by Dick Gilcreast in his article on the 21/3.4 and 21/4 lenses: http://www.lhsa.org/angulons.htm Here is the quote I am puzzling over but please read the whole article to get everything in context: "The 21mm f/3.4 Super-Angulon is very sharp and relatively reflection free at all apertures. And, unlike a retrofocus design, it can be handheld at quite long shutter speeds because of the very short distance between its principal plane (where the diaphragm is located) and the film." Now why would there be a difference in the effects of camera shake between symmetrical and retrofocus designs of the same focal length? It does not make sense to me but that is hardly surprising as I was repeatedly dropped on my head in my youth and thus am unable to understand the simplest of concepts (such as the point of the UV filter thread for instance). Please shed some light into the great void that is my brain. Cheers, Puzzled in Alberta ====================================================================== Dear Puzzled, I, too, had to think hard about this one. I can only guess that the author is referring to the effect on the image of slight angular movement of the camera during exposure, due to camera shake. The shorter the lens-to-film plane distance, the less the effect on the image. That makes sense to me, anyway! It's easier to understand this if we consider an extreme (if improbable) example. Imagine, for instance, a design where the lens rear element is 100mm from the film, compared with one where the distance is only 1mm. In the former case, angular movement would cause a much larger movement of the image compared to the latter case. Somebody please correct me if I'm wrong . . . please . . . ? As regards the point of the UV thread, I think its frequent recurrence is an indication of the dynamic nature of the LUG: lots of new members seeking conventional wisdom from those who know the answers. They are afraid of spoiling their precious Leica lenses, either by using a UV filter or by not using one, depending on which is the lesser of the two evils. Whatever, they know they will always receive courteous and helpful treatment in this, the greatest of all photographic forums. Who knows, it might have even helped if you had been protected by a UV filter when being dropped on your head? I will now run for cover. Flame away, me hearties! I will protect myself from the heat asbestos I can. ;-) Regards, ===== Ray "The trouble with resisting temptation is you never know when you'll get another chance!" __________________________________________________ Do You Yahoo!? Get email at your own domain with Yahoo! Mail. http://personal.mail.yahoo.com/