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  1. #21
    AgX
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    The terminology on these matters is vague.

    I would distinguish between:

    -) perspective distortion

    -) geometric distortion

    -) lens distortion

    I admit that these terms too are ambiguous.

  2. #22

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    Quote Originally Posted by Bill Burk View Post
    Enjoyed the lens design story, thanks georg16nik.

    As several have noted... In terms of ease of focus and composition... rangefinders are well suited to wide angle, while SLR's are better suited to telephoto.
    Bill,

    I've never had a problem focusing a (Nikon) WA. One must only pull the split prism to the point you want focused and turn the camera a bit, if necessary, to get some angle across the split. Focus, compose and done. This works for me down to f/3.5, the slowest WA I have (28mm non-Ai). I'm 58 so we'll see what my eyes have to say about this going forward. Additionally an RF, unless I use an external viewfinder, does not show me the 'distortion' a WA provides, only its FOV, an SLR cannot avoid showing both. I am often after just that and it helps composition to be able to see it.

    Having the muscle memory to pull that split prism around, now that I own an M3 one would think it would be easy to remember that I have to pull that split image around too. But I'm having a hell of a time remembering that when things are moving fast (My kingdom for a ground glass!). This might help explain the popularity of 35mm lenses for RFs; the DOF makes it easier to go all HCB on it.

    s-a
    I photograph things to see what things look like photographed.
    - Garry Winogrand

  3. #23
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    Quote Originally Posted by semi-ambivalent View Post
    Michael,

    In the late 70s a "teacher" at the traveling Nikon School said wide angles don't have distortion but exaggerated perspective. He followed with a sensible proof using the ratio of distance to foreground objects and distance to background objects. Whether or not this was provided to explain away true distortion in WA Nikkors versus WAs by Leitz I don't know but 1) It made perfect sense, and 2) I've never had much problem with "distortion" if I framed the image correctly.
    "Distortion" is a lens defect. Some people use the term "geometric distortion" to express the typical wide-angle perspective. Some other people call that wide-angle perspective "distortion" but that really is incorrect IMO. The teacher was probably explaining them that that is not "distortion" but has a geometrical - optical explanation and is, therefore, unavoidable and perfectly normal.

    That said, wide angles have distortion proper just like any other lenses.
    Fabrizio Ruggeri fine art photography site: http://fabrizio-ruggeri.artistwebsites.com
    Stock images at Imagebroker: http://www.imagebroker.com/#/search/ib_fbr

  4. #24

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    I am referring specifically to geometric distortion, not wide angle perspective "stretching". The distortion I refer to is the failure of the lens to form a true rectilinear image due to asymmetry and the position of the diaphragm. These compromises cause either barrel distortion (straight lines "bow" outward, most visible along the edges of the frame), pincushion distortion (the opposite of barrel) or complex distortion (a combination of barrel and pincushion - typically barrel transitioning to pincushion toward the corners, hence the term "mustache" often used to describe it). Generally in retrofocus lenses barrel distortion is the common defect while pincushion distortion usually affects telephoto designs (to a lesser degree) although either type of distortion (or both) can be present in both long and short focal lengths.

    Wide angle RF lenses typically suffer significantly less barrel distortion than SLR retrofocus wides.

  5. #25
    Bill Burk's Avatar
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    semi-ambivalent,

    I guess I too never have any real "problem" focusing wide angle with an SLR. And I also have no trouble focusing a 90mm with M2... It's just that it seems relatively easier (since focus patch is the same for any lens) to focus the rangefinder with wide angle...

  6. #26

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    Quote Originally Posted by Bill Burk View Post
    semi-ambivalent,

    I guess I too never have any real "problem" focusing wide angle with an SLR. And I also have no trouble focusing a 90mm with M2... It's just that it seems relatively easier (since focus patch is the same for any lens) to focus the rangefinder with wide angle...
    Bill,

    Not trying to pick a quarrel here. I'm certainly having problems teaching my brain RF-mode, but none of the 'problems' I'm having relate to the supposed benefits/weaknesses of RF/SLR that are at the nucleus of most of the gentlemanly bickering that goes on about such subjects. It sometimes sounds like both camps have circled the wagons, and stalemate ensued.

    s-a
    I photograph things to see what things look like photographed.
    - Garry Winogrand

  7. #27
    Bill Burk's Avatar
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    Quote Originally Posted by semi-ambivalent View Post
    Bill,

    Not trying to pick a quarrel here.
    Thought never occurred to me...

    I guess it's more a "strengths" issue, not really a problem. Take 50mm as neutral. Both RF and SLR work well at normal. Then put a wide angle on an SLR and everything kind of always seems in focus (because of the greater depth of field). So this could cause a focus error. While a rangefinder will encourage you to focus just as accurately.

    Then put a slight telephoto on an SLR and start taking portrait photos. It's just pure fun. While the rangefinder with a telephoto just seems like a kludge. The M2 did a good workaround by moving the framelines. But my Contax didn't - requires accessory finder or guesswork.

  8. #28
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    Quote Originally Posted by Bill Burk View Post
    Enjoyed the lens design story, thanks georg16nik.

    As several have noted... In terms of ease of focus and composition... rangefinders are well suited to wide angle, while SLR's are better suited to telephoto.
    Bill, You are welcome!

    I don't see SLR lens designers fooling themselves that something could be improved (at a reasonable cost) in SLR wides. Probably most users are totally cool with distortion even in 50mm. After all, its not big deal if You shoot cats.

    Nikon and the rest did their best and with current photo manipulation techniques, distortion is just "one of those things" to be taken care of.
    The Zeiss Sonnar "look" is probably a menu item in some software by now.

    IMHO, no RF lens improvements appeared in the recent decades.. the firm base was reached in the 50's.
    If You print optically from film and You shoot RF LTM (or M39), then using the same camera lens on Your enlarger might be revealing.

  9. #29
    Steve Smith's Avatar
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    Quote Originally Posted by David Lyga View Post
    Very interesting how retro-focus can actually be an advantage.
    I hink it's probably even more of an advantage with that alternative. electrical image recording technology.


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  10. #30
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    Quote Originally Posted by Michael R 1974 View Post
    I am referring specifically to geometric distortion, not wide angle perspective "stretching". The distortion I refer to is the failure of the lens to form a true rectilinear image due to asymmetry and the position of the diaphragm. These compromises cause either barrel distortion (straight lines "bow" outward, most visible along the edges of the frame), pincushion distortion (the opposite of barrel) or complex distortion (a combination of barrel and pincushion - typically barrel transitioning to pincushion toward the corners, hence the term "mustache" often used to describe it). Generally in retrofocus lenses barrel distortion is the common defect while pincushion distortion usually affects telephoto designs (to a lesser degree) although either type of distortion (or both) can be present in both long and short focal lengths.

    Wide angle RF lenses typically suffer significantly less barrel distortion than SLR retrofocus wides.
    I understand. I thought it was generally accepted to call barrel/pincushion/moustache distortion simply "distortion" (or lens distortion) while the "wide-angle perspective stretching" is I thought it were generally referred to as "geometric distortion" meaning it's the result of a law of geometry (nothing to do with the lens scheme or quality), but I see usage is not uniform and consequently there will always be a certain amount of ambiguity when talking about distortion of wide-angle lens.
    Fabrizio Ruggeri fine art photography site: http://fabrizio-ruggeri.artistwebsites.com
    Stock images at Imagebroker: http://www.imagebroker.com/#/search/ib_fbr

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