Digi lenses on Lf.

Discussion in 'Large Format Cameras and Accessories' started by Markok765, Aug 16, 2006.

  1. Markok765

    Markok765 Member

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    I have found out that when you zoom a zoom to the larger numbers eg 70-200 lenses the inage circle gets larger.so would lenses like the tamrom 30 -300mm f 4.5-6.3 be able to cover lf
     
  2. donbga

    donbga Member

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    Not even close, it wouldn't even cover 127 or 645.
     
  3. tommy5c

    tommy5c Member

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    I can see that some pieces are starting to click with you marko, it is a good discovery. but understand that those lenses are designed to cover something the size of your thumbnail at best. keep learning and discovering.
     
  4. Markok765

    Markok765 Member

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    yes, but the 10x zoom would give a decent inage circle at 300mm i think.
     
  5. HerrBremerhaven

    HerrBremerhaven Member

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    Hello Marko,

    I know from a little experimenting with Nikon lenses that a few will cover more than 24mm by 36mm. The obvious ones are the Nikon shift lenses, which will cover 6x4.5 or slighly better. The not so obvious would be the old 300mm f2.8, which should also cover 6x4.5. Outside of those, a handful of wide and superwide lenses cover near 6x4.5 when stopped down a bit. All are very far off from covering large format.

    Ciao!

    Gordon Moat
    A G Studio
     
  6. smieglitz

    smieglitz Member

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    Marko,

    If you are interested in seeing the actual coverage and you lack a LF camera, take a sheet of white paper and tape it to the wall opposite a large window. Mark off the format you are interested in on the paper (4x5, 5x7, 8x10, etc.). Obtain a cardboard box that has sides slightly less than the focal length you are interested in (e.g., a box 10" high for a 300mm or 12inch lens) and cut a whole in the bottom where you can slide the lens through. Have the other end of the box open and use tape or cloth to block any light that might come in around the hole. With the lens at a distance from the wall/paper approximately equal to the focal length you should be able to see whether or not the lens will cover the format at infinity. To do this move the lens/box toward or away from the wall until the distant bright outdoor scene beyond the window comes into focus. Moving the box/lens further from the wall will show the increased coverage as you progressively focus on closer objects (e.g., the window frame).

    I think you will find as others have stated that the image circle cast for a lens of a certain focal length designed for 35mm use will be smaller than you might expect at infinity due to the design considerations. Lenses designed for large format will have much larger image circles due to their wider-angle designs. That also brings up another point. The terms "wide-angle" and "telephoto" refer to lens designs and are not really synonymous with the shorter- or longer-than-normal focal lengths. You can have a single lens of a certain design that would be a normal focal length for one format and a short focal length for another format and still cover. An example would be my 210mm Schneider Angulon. It is a wide-angle lens design that will just cover my 11x14 and thus be a short focal length lens for that format, but it would be a normal to slightly long focal length lens when used on my 5x7 format camera.

    Joe
     
  7. raucousimages

    raucousimages Member

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    How do you plan on operating the electronic diaphragm and what are you going to use as a shutter? Not to mention mounting a lens on a board. But if you want to, go for it. I think the best you will ever find is in image circle of about 40mm.
     
  8. Sparky

    Sparky Member

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    Don't be so hard on the guy, peeps. That's not always the case. Several RB lenses, for example, cover 4x5. I've used a micro nikkor 55 on a 4x5 and got it to almost cover at 1:1 (special case, I know...).

    I think it's generally true that any NON retrofocus lens (this puts out zooms) would stand a much better chance of covering larger formats.
     
  9. Steve Smith

    Steve Smith Member

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    The image circle will increase the closer the lens is to the subject and the further away the lens is from the film i.e. for macro use. That's why some people get good results using enlarger lenses as macro lenses on LF cameras. An enlarger is really a macro camera with the lens being close to the subject (the negative) and the film (or paper) being further away. Most enlarger lenses, if used as a traditional lens focused around infinity will not have a very large image circle. But use them in an enlarger and they have no problem projecting an image onto the larger sizes of paper.

    Bearing this in mind, I would expect that many 35mm lenses could cover 5x4 (for example) but only if used at extreme macro settings.


    Steve.
     
  10. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    Indeed, many 35mm lenses will cover larger formats for macro/micro use, but that's a fairly special case. Here's one of mine--

    http://www.apug.org/gallery/showphoto.php?photo=7389&cat=500&ppuser=60

    Some 35mm lenses might cover larger formats with modifications, since they are usually baffled to restrict coverage to the 35mm frame and minimize flare, but if the baffles are removed, they won't make very good 35mm lenses anymore, and after some potentially complicated disassembly, you might discover that they aren't very sharp outside their intended image circle.

    Some of the older super-teles might cover, if the head is removed from the focusing helical (they were often designed that way), but then you need to work out a shutter, if you happen to have one of these lenses.
     
  11. Ole

    Ole Moderator Staff Member Moderator

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    There are also a lot of "intermediate length" lenses that are constructed like "normal" lenses. Most 35mm users equate "telephoto" with "longer than 50mm", but many lenses up to about 200mm are really normal lenses. All they need to be MF (or sometimes LF) lenses is a hacksaw to remove the rear half. Sometimes not even that - the Leitz 135mm Hektor simply unscrews. What you're left with is an extension tube, and a 135mm Tessar-type lens in helical focusing mount.
     
  12. raucousimages

    raucousimages Member

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    Use the right tool for the job. Why try to reinvent the wheel? Besides if you start cutting lenses in half that realy messes with the electronics for the iris or do want to cut a hole in the side and make waterhouse stops? And I still want to know about the shutter.
     
  13. Anupam Basu

    Anupam Basu Member

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    Wouldn't it need to be 46.5mm from the film plane to focus on infinity? And at that distance I imagine the image circle would be pretty small.

    -A
     
  14. Dan Fromm

    Dan Fromm Member

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    Anupam, the "cut the rear section off of a long focus lens" trick works, when it does, because the lens is just an achromatic doublet hung way out in front of the film plane. We're used to more complex constructions, but some well-respected third-party lens makers made such simple long lenses. Century Precision Optics, for one, also Kilfitt and Novoflex.

    46.5 mm is the Nikon F flange-to-film distance. Most other SLR mounts' -- yes, Nikon isn't the only one -- flange-to-film distances are shorter.

    Cheers,

    Dan