Apochromat vs. Photo lens.

Does anyone know how well a similar aperture multi-element photographic
lens stacks up to an apochromatic triplet or ED type lens? Is colour
correction better or the same with either for astro-imaging? What about
field flatness, sharpness, etc.

On Fri, 06 Feb 2004 23:21:28 GMT, "Ed Majden" wrote:

Does anyone know how well a similar aperture multi-element photographic
lens stacks up to an apochromatic triplet or ED type lens? Is colour
correction better or the same with either for astro-imaging? What about
field flatness, sharpness, etc.

Generally, very badly. Camera lenses, even very good ones, have specs that don't
approach even fair telescopes. They represent a compromised design in order to
get a wide, flat image a very short distance behind the rear element.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Fri, 06 Feb 2004 23:21:28 GMT, "Ed Majden" wrote:

Does anyone know how well a similar aperture multi-element photographic
lens stacks up to an apochromatic triplet or ED type lens? Is colour
correction better or the same with either for astro-imaging? What about
field flatness, sharpness, etc.

Generally, very badly. Camera lenses, even very good ones, have specs that don't
approach even fair telescopes. They represent a compromised design in order to
get a wide, flat image a very short distance behind the rear element.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Does anyone know how well a similar aperture multi-element photographic
lens stacks up to an apochromatic triplet or ED type lens? Is colour
correction better or the same with either for astro-imaging? What about
field flatness, sharpness, etc.

Hi:

Much worse in every regard.

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
Goto http://members.aol.com/RMOLLISE/index.html

Does anyone know how well a similar aperture multi-element photographic
lens stacks up to an apochromatic triplet or ED type lens? Is colour
correction better or the same with either for astro-imaging? What about
field flatness, sharpness, etc.

Hi:

Much worse in every regard.

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
Goto http://members.aol.com/RMOLLISE/index.html

Rod Mollise wrote:

Does anyone know how well a similar aperture multi-element photographic
lens stacks up to an apochromatic triplet or ED type lens? Is colour
correction better or the same with either for astro-imaging? What about
field flatness, sharpness, etc.

Hi:

Much worse in every regard.

If a camera did have a good telescope quality lens system, would it make
any significant improvement in the final image with either prints or
slides?


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Rod Mollise wrote:

Does anyone know how well a similar aperture multi-element photographic
lens stacks up to an apochromatic triplet or ED type lens? Is colour
correction better or the same with either for astro-imaging? What about
field flatness, sharpness, etc.

Hi:

Much worse in every regard.

If a camera did have a good telescope quality lens system, would it make
any significant improvement in the final image with either prints or
slides?


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http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

On Fri, 06 Feb 2004 23:21:28 GMT, Ed Majden wrote:

Does anyone know how well a similar aperture multi-element photographic
lens stacks up to an apochromatic triplet or ED type lens? Is colour
correction better or the same with either for astro-imaging? What about
field flatness, sharpness, etc.

As others have told you, camera lenses do not fair well against
telescopes.

One obvious reason that no one so far mentioned is that camera lenses
aren't expected to be used visually. Aberrations which would be
detrimental to visual use aren't necessarily a problem with photographic
use, due to the much lower resolution of film (and CCDs) compared with
your eye.

Therefore, much that would be objectionable in a visual system is
tolerated to achieve a flat field with an extremely short focal length - a
typical 35mm lens has a 50mm focal length, with a focal ratio down to less
than f/2 with the iris wide open.


--
- Mike

Remove 'spambegone.net' and reverse to send e-mail.

On Fri, 06 Feb 2004 23:21:28 GMT, Ed Majden wrote:

Does anyone know how well a similar aperture multi-element photographic
lens stacks up to an apochromatic triplet or ED type lens? Is colour
correction better or the same with either for astro-imaging? What about
field flatness, sharpness, etc.

As others have told you, camera lenses do not fair well against
telescopes.

One obvious reason that no one so far mentioned is that camera lenses
aren't expected to be used visually. Aberrations which would be
detrimental to visual use aren't necessarily a problem with photographic
use, due to the much lower resolution of film (and CCDs) compared with
your eye.

Therefore, much that would be objectionable in a visual system is
tolerated to achieve a flat field with an extremely short focal length - a
typical 35mm lens has a 50mm focal length, with a focal ratio down to less
than f/2 with the iris wide open.


--
- Mike

Remove 'spambegone.net' and reverse to send e-mail.

Think about this. A photographic multi-element lens is generally
NOT designed with the same purpose in mind as a telescope lens
and definately not apo lenses. They are just different animals.
(burros vs race horses).

Jerry

Ed Majden wrote:

Does anyone know how well a similar aperture multi-element photographic
lens stacks up to an apochromatic triplet or ED type lens? Is colour
correction better or the same with either for astro-imaging? What about
field flatness, sharpness, etc.