----- Original Message ----- From: "enitka" <enitka@twcny.rr.com> To: "List for Photo/Imaging Educators - Professionals - Students" <photoforum@listserver.isc.rit.edu> Sent: Tuesday, December 24, 2002 10:27 AM Subject: RE: Fast Lenses: Why so expensive? > Kevin - it has nothing really to do with the diaphragm - it has all > to do with the physics of correcting light to produce an acceptable > image. It is the engineering This is called the Gauss effect, by the physicist Gauss (Hermann, I think) whose mathematics for calculating the space between the elements, front verses rear, is still used today. >and in many instances the use of > special glass All lenses are made with 'Shot Glass' named for the family who produced glass for optics used in camera lenses. Wisner tried to fiddle with the formula, but it is still Shot Glass. Fuji began production on a pure crystol glass, but that was mainly in an experiment to better capture light for digital cameras. >such as aspherical lens surfaces. The exterior shape of the lens has to do with the ability to retain an image projection to the rear, the film plane without stigma : termed ana (wihout any) stigmatic (stigmas). Some development has advanced on submarine periscope lenses to give wide angle, and fast (clear dispersion for wide angles) like the Biogon lens; but essentially the cost has to do with engineering and assembly of these extra elemants, as ernie says. Your previous > impression about the speed of opening up the diaphragm doesn't add to > the expense of the lens and in the case of rangefinder lenses there > is no opening or closing of the aperture once it is set on the lens. > > ernie > > > >I previously was under the impresson the the diaphragm opened when > >the picture is taken. I theorised that a fast lens was fast because > >a diapragm opening to f/1.4 @ 1/1000 would be faster than a lens > >that opened to > >f/5.6 @ 1/1000. Obviously that isn't the case. > >There is much that I do not understand regarding the physics of > >light. It just seems from a non-engineering point of view that > >building a lens with a large aperture shouldn't be any more > >expensive than a lens with a small aperture. > > > > > >Kevin > > > > -----Original Message----- > > From: Ernest Nitka [mailto:enitka@twcny.rr.com] > > Sent: Tue 12/24/2002 12:17 PM > > To: List for Photo/Imaging Educators - Professionals - Students > > Cc: > > Subject: Re: Fast Lenses: Why so expensive? > > > > > > > > Kevin - simply put the faster the lens the more correction has to be > > designed into the lens so the distortions don't get the best of the > > image. The opposite of this design requirement is the pin > >hole camera - a > > hole without a lens at say f/256 will give you an image > >albeit not terribly > > sharp. The more technical on the list can give you all the > >technical reasons. > > > > ernie > > > > > above incert, Steve Shapiro, Carmel, CA Happy Holidays!
