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  1. #51
    AgX
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    Quote Originally Posted by darinwc View Post
    Actually benjiboy is incorrect. Diapositivo was referring to barrel or pincushion distortion, where straight lines bend due to lens distortion.

    Converging verticals, a result of the angle of the camera, is not 'distortion', it is just perspective. The lines of a building will still be perfectly straight.
    Perspective distorsion refers to extreme difference in reproduction scale within a subject. This will be due to the subject-camera distance being of the magnitude as the distances within the subject itself. This is easily achieved by employing wide-angle lenses.

    Though those converging lines are a matter of perspective or rather the inclination between subject- and film plane, the angle of convergence can be influenced by perspective distorsion. Thus both phenoma can add to each other.

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    The problem I have with 35mm rangefinders is the imprecise framing. I shoot a lot of buildings and I often create formal (symmetrical) compositions. I sometimes notice barrel distortion in photos made with my Nikon wides; the actual amount seems to vary based on focus distance, and the noticeability is highly dependent on the subject. Despite that, I can’t imagine doing what I do without a 100% accurate viewfinder with a grid.

    Is there such a thing as an “architecture” 35mm rangefinder? Ideally, it’d have both the hot shoe and the tripod socket centered directly above and below the lens, so all one would need to worry about was parallax on the x-axis. Why do so many rangefinders have offset hot shoes and tripod sockets anyway? Are there any highly-corrected accessory viewfinders with grids?

    The obvious solution would be to simply use a digital camera or move up to a larger film format, but it’s still fun to think about.

  3. #53
    Ian Grant's Avatar
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    Interesting questions. I use LF cameras handhe;d with the wire frame finders and wide angle lenses and shoot with a 6x17 camera and a view finder with no issues, I think you quickly learn the camears. In the months I shot with a 21mm Leitz lens and its finder I never had any problems either.

    Ian

  4. #54
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    Wiltw quote: "back when computers were not used for lens design"

    My question: What was the year that things changed? Or please give a short continuum of years defining the (sudden or gradual?) 'improvement' in zooms due to computer determination of formula, as opposed to manual determination. My rudimentary guess is the 'late 70s'. - David Lyga

  5. #55
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    Quote Originally Posted by benjiboy View Post
    These distortions are a red herring, because they not because of inherent lens aberrations but because the camera has been pointed upwards to cause perspective distortion because it wasn't capable of lens movements in relation to the film plane.
    What I mean is that those pictures DON'T show barrel or pincushion distortion because either it was not there or it was corrected (guess how). The perspective effect, the convergence of lines toward a vanishing point, is not "distortion". Why people lie this word so much that they use always use it?

    "Distortion" is a lens defect and in images like those, when uncorrected, would show very clearly and would disturb the subject a lot.

    Distorted means deformed, wrong, weird, not-straight. Geometric and perspective effects should be rendered with some other word than "distortion" because they are perfectly normal real-world phenomena and show nothing "deformed".

    I understand that people use the term geometric or perspective "distortion" when talking about the exaggerated nose of somebody photographed with a wide-angle lens from short distance.

    But in general how do we define "barrel-pincushion/moustache distortion"? Should we define each time "of the barrel-pincushion kind" to be clear?
    Last edited by Diapositivo; 11-19-2012 at 03:47 PM. Click to view previous post history.
    Fabrizio Ruggeri fine art photography site: http://fabrizio-ruggeri.artistwebsites.com
    Stock images at Imagebroker: http://www.imagebroker.com/#/search/ib_fbr

  6. #56

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    Quote Originally Posted by David Lyga View Post
    Wiltw quote: "back when computers were not used for lens design"

    My question: What was the year that things changed? Or please give a short continuum of years defining the (sudden or gradual?) 'improvement' in zooms due to computer determination of formula, as opposed to manual determination. My rudimentary guess is the 'late 70s'. - David Lyga


    http://www.laserfocusworld.com/artic...o-pioneer.html

  7. #57
    Poisson Du Jour's Avatar
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    Quote Originally Posted by Diapositivo View Post
    [...]
    Distorted means deformed, wrong, weird, not-straight.


    You talkin' about me — while I'm playin' with my glo-flies (instead of cameras)!?
    .::Gary Rowan Higgins

    A comfort zone is a wonderful place. But nothing ever grows there.
    —Anon.






  8. #58
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    Quote Originally Posted by David Lyga View Post
    Wiltw quote: "back when computers were not used for lens design"

    My question: What was the year that things changed? Or please give a short continuum of years defining the (sudden or gradual?) 'improvement' in zooms due to computer determination of formula, as opposed to manual determination. My rudimentary guess is the 'late 70s'. - David Lyga
    Throughout the early Eighties old-school "hand-designed" lenses coexisted with computer-generated lenses. I think by 1985 most lenses were computer-designed. I remember a lens test showing a recent Nikon SE lens performing much better than the more expensive, heavier, old-design Nikkor. (OK it was heavier also because it was better realized mechanically). Must have been 1985 or so.

    I think it was just at that time that Leitz made an agreement with Minolta for the realization of their first zooms (based on Minolta designs). Leitz being a small, quasi-artisanal firm did not have or could not afford a research centre able to deal with the new design tecniques, I imagine. Computer-aided design made zoom lenses possible for photographic purposes. Until then they were basically only seen in the motion picture industry or in small movie cameras. "Turrets" or "bifocals" were the alternatives.
    Fabrizio Ruggeri fine art photography site: http://fabrizio-ruggeri.artistwebsites.com
    Stock images at Imagebroker: http://www.imagebroker.com/#/search/ib_fbr

  9. #59

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    This image was taken on my Canham MQC 5x7 using a 72mm Super Angulon (circa approx 16mm as regards 35mm) with a yellow filter. No lens correction was carried out in PS.


    Venford Dam 72mm SA XL yellow 5x7 1200 Wet by Ed Bray, on Flickr

  10. #60
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    Quote Originally Posted by David Lyga View Post
    Wiltw quote: "back when computers were not used for lens design"

    My question: What was the year that things changed? Or please give a short continuum of years defining the (sudden or gradual?) 'improvement' in zooms due to computer determination of formula, as opposed to manual determination. My rudimentary guess is the 'late 70s'. - David Lyga
    The really powerful yet relatively affordable minicomputers, like the Digital Equipment Corp VAX computer, really came about in the mid 1970s. The much less affordable IBM 360 mainframe had been out about 10 years earlier, but not in broad use...I remember that in 1969 my bank (Wells Fargo) had to make phone calls from branch to branch 30 miles apart, simply to verify that I had enough money in my account to get a $20 cash withdrawal (back when $20 could buy 66 gallons of gas!).

    Not being an optical designer, I would have to guess about when computers became much more prevalent among lens designing companies, and more ownable outside government and defense circles. It seems that short ratio (2:1)zoom lenses became much better about the mid 70's, so I speculate that was the result of more computerization becoming part of the design process, rather than slide rules!
    Last edited by wiltw; 11-19-2012 at 04:13 PM. Click to view previous post history.

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