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Thread: Please Help With Graphic-Kowa 150 and 210mm Spacing in Shutter

  1. #1

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    Please Help With Graphic-Kowa 150 and 210mm Spacing in Shutter

    Can anyone who has a Graphic Kowa lens factory mounted or professionally mounted in a Copal 1 shutter please measure the overall length of the lens cells in shutter? I'm interested in the spacing of both the 150 and 210mm focal lengths.

    I bought both focal lengths in barrel, and while the cells screw directly into my Copal 1, I suspect something is amiss with the 150mm lens. When screwed all the way in to the shutter, my 150mm measures 38.15mm overall length. The resulting image covers 8x10, and while super sharp in the center, sharpness quickly degrades to mush 2-3 inches from the edges. When I unscrew the cells nearly all the way, to obtain 42.5 mm overall length in shutter, I get much improved sharpness over a smaller (about 260mm) image circle. My ultimate goal for this lens is to cover both 4x5 and 4x10.

    While trial and error shows an improvement with increased spacing in the 150mm lens, I don't know the ideal distance I should be trying to achieve, and being off by several millimeters makes me queasy.

    I've been very happy with the performance of my 210mm G-K on 8x10 at an overall length of 38.75mm fully screwed into the shutter, but I'd love to compare this distance with a professional or factory mounted specimen.

    Thank you in advance to any who can contribute. These lenses are wonderful performers with absurdly large coverage for their diminutive size. But, as the annals of this forum attest, their specs are shrouded in mystery.

  2. #2
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    Re: Please Help With Graphic-Kowa 150 and 210mm Spacing in Shutter

    I'll check tomorrow on the 210 GK mine is in a copal 1, while a second I purchased to get rid of some bad mojo from the first has a spacer ring, I'll measure both (I've been meaning to anyway).

    The 150 GK isn't supposed to cover 8x10 (and by cover I mean cover with sharpness) so that's probably why. But I'm curious about the spacing.

  3. #3

    Re: Please Help With Graphic-Kowa 150 and 210mm Spacing in Shutter

    Seems like the 150 should be the same length it was in the barrel, no?

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    Re: Please Help With Graphic-Kowa 150 and 210mm Spacing in Shutter

    Quote Originally Posted by Chauncey Walden View Post
    Seems like the 150 should be the same length it was in the barrel, no?
    +1

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    Re: Please Help With Graphic-Kowa 150 and 210mm Spacing in Shutter

    I had the same thought, and here is what I found: the length of my 150 in barrel is 39mm. But, when I unscrewed the cells about one and a half turns in shutter to match the barrel length, the results still looked poor on the ground glass within a few inches of the frame edge, even stopped down. Then it occurred to me that the spacing in barrel may not be optimized for a taking lens at infinity, so I appealed to forum users for their dimensions.

    I received a very helpful response by PM from a member who reported corner to corner 4x10 sharpness with the G-K 150. His factory mounted Kyvytar is 40.00mm overall length, including spacers. I'm going to try out this configuration, but I'm sill interested to hear other's experience with the spacing of the 150 and 210 in shutter as a taking lens.

    Thanks for your responses,
    Bill

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    Please Help With Graphic-Kowa 150 and 210mm Spacing in Shutter

    My 210 GK that is in the original barrel is 41.9mm and the one in my copal is 39.6mm the difference may be the absence of the spacer in the copal version, vs the barrel lens which has a brass spacer.

    This is interesting to me as I was told the shutter version was installed by SK Grimes, so you would think they would have kept the spacer, however lots of what the seller told me about this lens was exaggerated so it's possible it was "fiddled with" and the spacer was lost.

    I will say that wide open, the lens is fuzzy (even on the GG compared to other lenses I have) however when stopped down to f/22 it's pretty darn sharp.

    It's also possible that because this was a graphic lens, the spacer was removed purposefully because when used for camera work vs copy work, SK Grimes determined that the lens performed at infinity better with a different spacing than for copy work (just a possible theory?).

    I did measure twice but the tool I'm using only goes to 1.155 inches or so, so I took separate measurements of the front to back of lensboard and rear to back of other side of lensboard and then the lens board and subtracted the lensboard thickness from the total number for the GK in shutter, and did the same (using the flange ring as the middle point) and then subtracting the flange distance. Finally I converted the distance to metric, so it's possible I screwed up somewhere, but I measured twice with the same distances.

    Hope that's helpful.

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    Re: Please Help With Graphic-Kowa 150 and 210mm Spacing in Shutter

    Quote Originally Posted by Whir-Click View Post
    While trial and error shows an improvement with increased spacing in the 150mm lens, I don't know the ideal distance I should be trying to achieve, and being off by several millimeters makes me queasy. .
    For infinity focus, your on the right track. You might try some tests with film and the lens stopped down to confirm. The few lenses I spaced to improve field flatness at infinity at the wide margin of coverage, seemed to have more of a focus pattern like the picture below (exaggerated). In contrast to a simple parabola which I was expecting. My conclusion was there is no 'correct' spacing; everything is a compromise depending on the type of photograph you want to take.

    Click image for larger version. 

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    Re: Please Help With Graphic-Kowa 150 and 210mm Spacing in Shutter

    My 210mm f/9 Graphic-Kowa measures just shy of 39mm so it seems to be the same as yours. But I don't have a caliper so this is just a rough measurement with a ruler. It has oodles of coverage on 8x10, more than I can use from my experience. Contrary to Stone, mine is pretty sharp even wide-open.

    It is in a Copal #1 shutter. No idea who mounted it.

    Isn't there still some debate about the 210mm GK and whether or not it's the same design as the 210mm Computar, or some of them anyway?
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    Re: Please Help With Graphic-Kowa 150 and 210mm Spacing in Shutter

    Quote Originally Posted by Corran View Post
    My 210mm f/9 Graphic-Kowa measures just shy of 39mm so it seems to be the same as yours. But I don't have a caliper so this is just a rough measurement with a ruler. It has oodles of coverage on 8x10, more than I can use from my experience. Contrary to Stone, mine is pretty sharp even wide-open.

    It is in a Copal #1 shutter. No idea who mounted it.

    Isn't there still some debate about the 210mm GK and whether or not it's the same design as the 210mm Computar, or some of them anyway?
    I think so, but Sandy King did some comparisons at one point and to my recollection of his post it seemed the Computar didn't have as wide an IC but that could also be mechanical vignette, google it, you'll find his very thorough list of 210mm lenses and coverages on LFF or APUG I forget where it is.

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    Re: Please Help With Graphic-Kowa 150 and 210mm Spacing in Shutter

    No the Computar has more coverage (up to 11x14). But some GK's seem to be the same. I haven't seen any serial # lists - presumably if the design of the GK's changed at some point, there would be a rough estimate of when in the serials the change happened.

    I don't think anyone has had enough 210mm GK's and Computars in one place to do a thorough test (sample size). I put my GK on my 8x20 to look at the "real" image circle but now I can't even remember what I discovered.
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