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Thread: Aspherical, Apo(chromatic) & ED (extra low dispersion) lenses - whats the difference?

  1. #21

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    Re: Aspherical, Apo(chromatic) & ED (extra low dispersion) lenses - whats the differe

    This discussion has come up before..

    To even begin to achieve good performance from the lens, film flatness is a MUST. This is one of the fundamental reasons why going up in film format size makes achieving film flatness difficult. To deal with this problem adhesive and vacuum film holders can be used to help film flatness with increasing film size. Film flatness is one of the fundamental reasons why 8x10 can be a problem to realizing all a give lens can produce.

    Camera alignment is another significant factor, folder cameras might not have any where near the precision and repeatability of alignment of standards needed to achieve what the lens can render. Problem is increased with larger lens apertures used. This is why stopping down is often the solution to remedy both these problems.. except lens performance will be reduced as the image taking aperture shrinks... resulting in "sort-of-focus". Not much of a problem if contact prints are made from 8x10 or larger film, problem if the film is projection enlarger to any significant degree.

    Glass plates are flat, flatter than film in a film holder.. problem with camera precise and alignment remains regardless of how flat the image recoding device or media is.

    This is why process cameras back in the day had vacuum backs on a precision flat film back. Camera alignment was check, adjusted, calibrated. Using a vacuum film back large sheets of film (could be feet x feet in size) could be held remarkably flat as needed for precision graphics work.

    Simply going down film format size can make a surprising difference in easing film flatness problems.

    Lens performance is one factor out of many that will have an effect on the finished print.



    Bernice


    Quote Originally Posted by John Layton View Post
    This discussion is starting to make me wish that glass plates would make a comeback. Hmmm...maybe I need to connect with Jason? Panchro at ISO-2 could be limiting...or liberating? Ortho at ISO 25...hmmm - could work wonders for deep woods work, not so likely for open ocean images.

    Seriously...to have something so dimensionally stable (as glass plates) - I'd be stepping up to whatever challenges I'd need to overcome to realize this!

  2. #22

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    Re: Aspherical, Apo(chromatic) & ED (extra low dispersion) lenses - whats the differe

    How much image information is contained in the original sheet of film -vs- what can be recored by any image digitalizing device?

    Once the film image is digitized, information will not be identical to what was on film. Will digitization of the image be good enough, that depends on what the image goals are.


    Bernice

    Quote Originally Posted by pkr1979 View Post
    This is more interesting then I thought it would be. As far as I understand, though, is that a APO-corrected lens is useful for reproduction and scanning (with dslr) large format negatives with, while its not that important its aspherical as you can stop down anyway?

  3. #23
    Drew Wiley
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    Re: Aspherical, Apo(chromatic) & ED (extra low dispersion) lenses - whats the differe

    There are all kinds of different paths to optical design. But in our mortal realm, cost efficiency is always a factor in manufacture. We aren't the real large format photographers with real money because we use tripods and not observatories. And there has to be enough market demand for certain specific glass types. The realistic options have changed over time. Most of today's lenses involve computer design and are likely to exceed what "cult lenses" of former years could do in terms of specs. Image rendering personality is a somewhat different lens topic; and I'm personally unqualified to comment on the best kind of beer bottle glass for doing that.
    pkr - most brand-name 35mm macro lenses are going to be very well corrected. I wouldn't worry about it too much. You don't have to pay thousands of dollars. But anything that tiny is going to involve a compromise. Going from sheet film originals to small digi camera scans is sorta like trying to feed a pet hippo through a keyhole. Yes, I'm set up that way to make basic web-usable copies of prints; but that's a very low threshold and small scale of reproduction. All the prints themselves were printed optically right from sheet film originals.

  4. #24

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    Re: Aspherical, Apo(chromatic) & ED (extra low dispersion) lenses - whats the differe

    Bernice, the goal would be to get a digitized copy that contains as much as possible of the original information. Today I use a drumscanner I got at a reasonable price - and it works quite well.

    Drew, I’ll get that hippo through eventually ;-) I dont know to much about these pixel shift cameras, but I imagine this function should be very useful for 'scanning'... Im not getting a Fuji GFX 100 today (able to do pixelshift with the new firmware), but this technology is probably available at a more sensible price in ten years. A 'decent' lens is probably useful in such a setup. What I here you say though, is that Fujis 120 macro is probably going to be sufficient - not expecting you to be familiar with that particular lens that is :-)

    I have a Rodenstock APO 360mm repro Ive been using with my 8x10 and its the sharpest lens I have... I never really use it though... its just too clinical. Im sure its very, very useful for its intended use though.

  5. #25

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    Re: Aspherical, Apo(chromatic) & ED (extra low dispersion) lenses - whats the differe

    Theoretically, a GOOD drum scanner in proper operating condition and properly used should yield good scans from film to digital files.

    Never found any APO process lens (APO ronar, APO artar, APO nikkor and..) to be "clinical" they have excellent optical performance and color rendition and has been the far preferred table top lens from back in the color transparency days. They also make excellent longer than normal focal length lenses.


    Bernice

  6. #26
    Drew Wiley
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    Re: Aspherical, Apo(chromatic) & ED (extra low dispersion) lenses - whats the differe

    Bernice, what I would personally refer to as "clinical" in my own set of Apo Nikkor dialytes is that the out-of-focus blur or "bokeh" is rather busy and not nice and soft like my older Zeiss tessar f/9 process lens of comparable focal length is, although it too is very sharp and fully apo corrected. Some people might not find modern barrel process lenses ideal for things like portraiture or other selective focus applications.

  7. #27

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    Re: Aspherical, Apo(chromatic) & ED (extra low dispersion) lenses - whats the differe

    Yes Drew, for images that need most of not all of the image in focus by stopping down to f16 and smaller, not a lot wrong with an APO process lens as out of focus rendition becomes a LOT less important. When out of focus rendition at larger taking apertures, it's back to something like a Kodak Commercial or similar Ektar or Schneider Xenar.. All depends on what the image goal is.


    Bernice

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