bright viewfinder is not necessarily best

Discussion in 'Large Format Cameras and Accessories' started by RobC, Mar 20, 2008.

  1. RobC

    RobC Member

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    Some years ago I put a bosscreen on my technikardan. It made a big difference to the viewfinder brightness but I've always found it difficult to focus exactly.
    I just put back the original Linhof ground glass and using a 45 reflex viewer in dim light just after sunset, I was able to focus really accurately even though it is far less bright than the bosscreen.
    The crop is from a notice board to the left of the arched church door and is at 100% of scan resolutoin which was done at 3200dpi unsharpened. On the neg with a 6x loupe, I can read most of what is on that notice board so I'm really pleased I put the old GG back. It just seems to snap into focus unlike the bosscreen.
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    Last edited by a moderator: Aug 11, 2008
  2. darinwc

    darinwc Subscriber

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    why was the boss screen harder to focus? was it just not sharp or was there a 'hot spot'
     
  3. RobC

    RobC Member

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    It's because the granularity in the linhof gg is either in focus or not. There seems to be a point with the linhof glass that it just pops into focus which is obvious. With the bosscreen a little either side of focus is difficult to detect, especially in dim light. I seemed to get more images slightly off focus with the bosscreen. It could just be me but I'm pleased with going back to the linhof gg. I should have done it long ago.
     
  4. gbenaim

    gbenaim Member

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    I had a similar experience w an Beattie Intenscreen and then a regular satin snow gg. There was probably a 2 stop difference, but the satin snow was much sharper.
     
  5. ic-racer

    ic-racer Member

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    I have had this same experience with a Intenscreen. The brighter a screen is made, the closer it gets to an 'impossible-to-focus' aerial image.

    I remember using a Beaulieu movie camera in which the focusing screen could flip out of the way, so you could have the best of both worlds :smile:
     
  6. Chris Breitenstein

    Chris Breitenstein Member

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    I think that has something to do with the use of a Fresnel; It creates a distinct spiral pattern that is almost impossible to get a sharp focus through. I can see how that would definitely be a problem if you are making enlargements.

    yours;
     
  7. Steve Hamley

    Steve Hamley Member

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    Same experience with a Maxwell versus Ebony. I like the Ebony better because it "snaps" into focus. Granted the Maxwell is about 1/2 to a stop brighter, but it does not "snap" into focus. I think a lot of people want a "TV screen" with no granularity, but don't realize the effect granularity has on determining accurate focus.

    That said, a Maxwell for a wide angle may likely be a good thing.

    Cheers,

    Steve