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  1. #11
    Paul Sorensen's Avatar
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    Quote Originally Posted by kaiyen
    Is there a listing of what size holes are needed for which shutters? Is this just something you look at in the specs on the lens/shutter combo? Also, the lens board I have has threads already in it - would I need to somehow insert threads into a board if I made my own?
    Most lenses you see for sale (especially modern ones) will have a jam nut or flange. This seems to be much more of an issue with older lenses, especially since replacement can be a challenge. I think that copal 0 and compur 0 are about 35mm, copal and compur 1s are about 42mm and a copal 3 is about 62mm. A modern 210mm is most likely to be in a copal 1, possibly a compur of the same size.

    I do suspect that if you want to get a modern Japanese or German lens, you will want to make a new board for it, but it should be an extremely easy process.

    Have fun!

    Paul.

  2. #12

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    The interface between LF camera and lens is the lensboard. To adapt the lenboard to a particular lens, you need the correct diameter hole. Lensboards are almost never threaded. The threads are almost always on flanges or retaining rings that come with the lens. Since you see threads on your lensboard, it probably means that someone left a flange attached.

    S K Grimes has a webpage that explains the difference between mounting flanges and retainging rings: http://www.skgrimes.com/adapter/index.htm. A mounting flange has screw holes for screws to attach it to a thick lens board. These were popular with older cameras and thick wooden lensboards. Probably this is what is on the lensboard that came with your camera. If you could figure out which thread that you have, you could buy a shutter to fit. But I wouldn't bother, because it would restrict your choices.

    Modern shutters use retaining rings. These are basicially nuts. You insert insert the shutter from the front of the lens board (typically after unscrewing the rear lens cell) and thread on the retaining ring to clamp the shutter to the lensboard. S. K. Grimes and Schneider have tables giving the hole diameters for modern shutters, e.g., http://www.schneideroptics.com/photo...ries/shutters/. The hole diameters do not have to be nearly as accurage as suggested by Schneider's figures. A catch is that the board can't be too thick because the threads on the modern shutters aren't that long. On many thick wooden lensboards it is necessary to machine a rebate around the hole so that the retaining ring can get sufficient thread engagement.

    I hope this doesn't sound complicated. Basically is a simple system that allows using lenses of manufacturer X on camera of manufacter Y. It's easiest if you buy the flange or retaining ring with the shutter, then make the hole in the lensboard to match.

  3. #13
    kaiyen's Avatar
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    Thanks for all the information. I will look for a lens first, then make a lensboard to fit it. That's better, anyway, since I can bargain hunt more with a wider selection.

    One other question - I see many lenses are listed as having enough coverage for 4x5. Few list 5x7. I assume that I cannot just use any 4x5 lens of the correct FL on a 5x7. Other than comparing the image circle with a 5x7 film size, is there any rule of thumb about whether lens A or B will be sufficient? On ebay in particular, few lenses list all those specs, and that's a lot of info hunting...

    allan

  4. #14
    Paul Sorensen's Avatar
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    Quote Originally Posted by kaiyen
    Thanks for all the information. I will look for a lens first, then make a lensboard to fit it. That's better, anyway, since I can bargain hunt more with a wider selection.

    One other question - I see many lenses are listed as having enough coverage for 4x5. Few list 5x7. I assume that I cannot just use any 4x5 lens of the correct FL on a 5x7. Other than comparing the image circle with a 5x7 film size, is there any rule of thumb about whether lens A or B will be sufficient? On ebay in particular, few lenses list all those specs, and that's a lot of info hunting...

    allan
    Here is a list from largeformatphotography.info of lenses from the four main manufacturers that cover 5x7. Since you are not looking at new lenses, the fact that it has not been updated in three years will be of no consequence. (There may have been no lenses introduced in the last three years anyway!) You will see that most of the 210mm lenses have just over 300mm of image circle which should give you fine coverage for most situations. 210mm is a "normal" range lens for 5x7. If you want a longer lens, coverage will tend to be larger, for shorter lenses you need to be more careful.

    I am not familiar with all of these lenses, but just any 4x5 lens will not necessarily cover. Some will barely cover and some will show fall off in the corners.

    One thing to consider is the amount of movements that your camera has, if you can't take advantage of many movements than one of the smaller image circle lenses will probably suffice from the list above. If your camera has lots of movements and you intend to use them, make sure that you are getting a lens with a large image circle so you don't run out too quickly.

    Paul.

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