Randy S. Little
http://www.rslittle.com
On Sun, Oct 21, 2012 at 7:18 PM, karl shah-jenner <shahjen@xxxxxxxxxxxx> wrote:
----- Original Message ----- From: "Randy Little" <randyslittle@xxxxxxxxx>
To: "List for Photo/Imaging Educators - Professionals - Students" <photoforum@xxxxxxxxxxxxxxxxxx>
Sent: Monday, October 22, 2012 9:14 AM
Subject: Re: Mixing digital photography with analog photographyMy uderstanding of aspherical lenses is their only unique property is to reduce spherical aberations
Most of what makes a digital back work doesn't exist in the film camera.
So you would have to make some sort of interface that could talk to the
camera which doesn't exist on the cameras. So the only way it could work
is in full manual mode. Which doesn't sound like much of a problem until
you find out that the cost of the back would still be close to an entire
camera. As for curved sensors its possible. Kodak made one for Leica
that while not curved used a micro-lens on the sensor that was concave in
design so as to work film lenses. Digital lenses all have an aspherical
element in them that makes the light strike the sensor more or less
straight on.
my understanding of lenses that collimate the light so it strikes the sensor straight on is .. either they are situated a loooooong way from the sensor, or they are telecentric (pushing the exit puple the 'long way' required) - nothing else makes sense - and if either of these were the case we'd not be able to use 'film' lenses on digital sensor based video still cameras unless they had little prisms mounted above the sensors to focus the non-parallel light onto the sensors - which they all do.
...
"What is Telecentricity?
Telecentricity is a special property of certain multi-element lens designs
in which the chief rays for all points across the object or image are
collimated. For example, telecentricity occurs when the chief rays are
parallel to the optical axis, in object and/or image space. Another way of
describing telecentricity is to state that the entrance pupil and/or exit
pupil of the system is located at infinity"
"In a system with object space telecentricity, movement of the object
toward or away from the lens will not result in the image getting bigger or
smaller, " so there is no magnification based on distance from the lens /
subject (!)
http://en.wikipedia.org/wiki/Telecentric_lens
http://www.edmundoptics.com/technical-support/imaging/what-is-telecentricity/
