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Thread: the two canons

  1. #11

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    Quote Originally Posted by AgX View Post
    The speed difference is negligable, so one could think Canon made a high-end version and a version with lower image quality that is cheaper but still bears that prestigious under-1 speed mark.

    However your findings (confined to your two samples) show the opposite, the more expensive version is the minor. Seen that there is no practical speeed difference, that is puzzling. At first sight.


    With SLR lenses we got the phenomenon that at the largest aperture of the high-speed lenses the image quality is reduced. But still one gains one stop in speed AND at smaller apertures the lenses yield better image quality than their counterpart of lesser price and speed.

    In this case I could imagine that the image quality of the 1.7 lens would be better at smaller apertures than with 1.9 lens.
    Just a guess...
    With my Nikons, that was not my experience. I had two 50/1.4 and one 50/1.2, all late pre ai. I discovered that at f:2, the 50/2 Nikkor H was as good as or better than either of the faster lenses at the same (f:2) aperture. At f:4, still no edge to the faster lenses, and the 1.2 was a handful - a fair amount of flare even at smaller apertures due to all the area of all those big elements bouncing light around inside.
    I now have two of the f:2-Hs a 66 and a 70-71, they're the only Nikon 50s I have.

    But, the fact remains that an f:1.4/1.2 lens can sometimes get you a picture when a one stop slower lens won't.

  2. #12

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    Quote Originally Posted by David Lyga View Post
    Canon made the GIII17 and made a larger one similar in name, also Canonet. The GIII17 had the 1.7/40 and the larger one had the 1.9/45. I find an amazing difference is sharpness when used wide open. The 1.7/40 is soft and lacks contrast wide open while the 1.9/45 is stunningly sharp and contrasty at all apertures. Comments? - David Lyga
    The lens on your G-III needs to be calibrated, meaning the flange-back distance needs to be reset. The 40/1.7 on the G-III is a very good lens wide-open, sharp and contrasty, but if the register is off, you get mush.

    There was a long discussion on this subject over on RFF (or the Classic Camera Repair Forum) a few years back. One of the guys experimented with changing the flange-back distance on his G-III. Once properly calibrated, the results were quite good. If you know what you are doing, you can do it yourself. Not hard if I recall, but the effort is worth it.

    Jim B.

  3. #13

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    My QLIII17 must be a fluke. Just got it back a few months ago after a CLA and it is sharp wide open. That is if I get focus right.

  4. #14

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    Quote Originally Posted by rbender View Post
    My QLIII17 must be a fluke. Just got it back a few months ago after a CLA and it is sharp wide open. That is if I get focus right.
    Not a fluke, your flange distance is properly set. Makes all the difference in the world when the light rays leaving the lens converge where they are supposed to.

    Ji b.

  5. #15

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    This is interesting. I obtained a GIII 17 just last year but with too much other stuff going on I have not have had a chance to replace the light sealing foam and so the camera sits. From what some of you are saying the flange back distance is adjustable? Or is it just the infinity stop on the helical that is adjustable. So many cameras, so little time.

  6. #16

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    Remembering the year's old G-III tread on RFF, Canon used shims to fine tune the flange distance of the lens. Either careless assembly at the factory, or 30+ years of use can cause the register to be off. One of the guys on the RFF thread was quite adept at DIY repairs. He removed the lens from the camera and re-shimmed it. Made a world of difference.

    This is from memory, so I can't offer much more. My G-III is great wide-open so I assume I got one of the good ones.

    Jim B.

  7. #17
    David Lyga's Avatar
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    I guess I am confused with the term 'flange back distance'. I check for infinity by taking five identical photos (wide open aperture) of a distant skyscraper outside my window. I focus a bit before in focus, almost in focus, in focus, slightly beyond focus, then more beyond focus, all carefully measured on the focus ring. I then rack up my enlarger and, with a magnifying glass, carefully scrutinize as to which negative is truly sharpest. If other than the one that is 'in focus', I adjust the tiny screws on the bottom and top of the helical (take top and bottom off camera) in order to make the 'REAL' infinity on the focus turn be the maximum. It is tedious to do but I want 'actual' to match 'apparent' focus.

    Brian: Isn't is nice that APUG does not ban one for sacrilegious statements? Some forums do!!! (I won't mention names but take a look on the Lounge.) But, Brian, let's start a new religion (even though I am agnostic) called 'defame the GIII'. It is a great camera (when shooting at 2.8 or less) but the religion part is only to cause more people to open their collective eyes and see that truth sometimes trumps truisms. There is a culture out there (in diverse genres) that says: 'do not ever even think of knocking this' and such adherents will back up this threat with intimidation or worse. (Modern Art is probably the most striking example.) In the 70s it was fashionable to knock normal lenses and to ALWAYS prefer wides. With the digital age that mandate has had reason to become modified due to the small sensors. I love normal lenses, always have, and preferred the older focal length determinant of 55 or 58 as opposed to the more current 50, or even 45.

    rbender: This is curious. Are you sure that that image is TRULY sharp or merely acceptable? And the contrast? Did you compare at both 1.7 and 5.6. adjusting shutter speed accordingly? I might dispute you if I saw your negatives. Then, again, this is curious: it is possible that you just might be correct and I might be wrong. Don't think so but have seen enough in this life to place doubt on anything, even me!!! - David Lyga
    Last edited by David Lyga; 11-09-2013 at 09:51 AM. Click to view previous post history.

  8. #18
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    Quote Originally Posted by BrianShaw View Post
    The GIII/1.7 I had was only mediocre. I've heard folks say that it is amazingly sharp but I never experienced anything more amazing than snapshot quality. Maybe I should have looked for a 19 but dumped all interest in Canonet when I started using a RetinaIIIc. THAT camera is amazingly sharp!
    I do agree. I've had several and found them to be below par. The Retina IIIC/c beats the ql17 hands down as does the Retina IIa..
    Leicarfcam aka Colyn

  9. #19

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    Quote Originally Posted by David Lyga View Post
    I guess I am confused with the term 'flange back distance'………..
    The "flange back difference" is the distance from the lens mount to the film or sensor. It's measured in sub-millimeters. If it's off even a bit, the light rays leaving the lens won't focus where they should. I'm hardly an expert on this stuff but can tell you that when I sent my Canon 50/0.95 TV lens to Ken Ruth to be modified to be used on my Leica M3, he asked that I send him the camera too. He specifically calibrated the lens to be 27.80mm from the film plane on my M3. When you're talking about using a high speed lens wide-open, a precise flange distance is essential.

    Jim B.

  10. #20
    David Lyga's Avatar
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    OK, Mackinaw, but my tests for 'before' and 'beyond' focus determine this and then I correct for any discrepancy. The bottom line is this, that rear element must be a precise distance from that film plane for focus (infinity or not) to be correct. I use infinity because that is where I want to set that 'ultimate' focus ring at so it cannot turn beyond. - David Lyga

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