Lens boards, common sizes for 5x4 and 10x8

Discussion in 'Talk About Techniques' started by Michael Diblicek, Mar 27, 2017.

  1. David M

    David M Member

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    We began with lens boards; I've had a look at mine. They are mostly Sinar/Horseman/Inka type or Linhof type, both types with various hole sizes.
    The Sinar ones seem pretty consistent in thickness, so measuring one example should suffice. On the other hand, original, badged Linhof boards seem thicker than the much cheaper Chinese ones that I own. The light-trap ridges on the back might vary too, but I haven't checked this. You will have noticed that the position of the hole in Linhof boards can vary.
    All of them seem to work.
    I haven't measured the odd MPP etc boards that I seem to have accumulated.
    If third parties buy your cameras, then it seems very likely that they will be using their own collection of lens boards, over which you will have no control.
    My conclusion is that the there are two possible solutions. Firstly, to devise your own standard for lensboards and sell these to prospective users, who might then have to unmount their current lenses and re-mount them in your board. This seems an unlikely thing to happen.
    The second and simpler way would be to build in a degree of adjustment so that all variations, (including home-made ones for vintage lenses) could be used. I don't know your design, but often the sliders that fix the board are mounted at a slight angle. You may have a better system in mind. A screw fixing would work, for instance.
    One matter that has not been raised is the use of recessed lensboards. The shape of these seems to have no standard at all and some boards will not fit some cameras, or require more force than is comfortable. Your design may eliminate the need for these. That would be a blessing.
    We might care to remember the history of LF cameras. For most of their history, they have been made by a cottage industry. See the history of the Gandolfi family as an example. A good deal of information would have been passed from father to son or master to apprentice and never written down at all; there would have been no need. Hence the paucity of archives.
    Best of luck, all the same. I'm sure that everyone on this forum will be delighted to see the finished cameras.
     
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  2. Michael Diblicek

    Michael Diblicek New Member

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    Hi Keith,

    Thanks for getting back and sorry for the delay in responding.

    Yes, of course their are ways of going about posing a question, and i could have posed it differently.

    When you say "and I cannot think of any other reason why you received such hostile receptions." it's not so much hostile responses. When i asked someone last year for the 5x4 film holder dimensions, i got some great information from some, and a couple of, shall we say not so good responses, and to put it plainly arrogant and rude responses, i'm not going into all the details on this or where, but in general 90% of people have been very positive and free in their experiences and information, but i found that a lot of people seems reluctant to share a lot of the fine details.

    I think we can put this to bed now, as i think the thickness of lens boards has been answered.

    I hope you get to see a finished camera too, so if all goes well that will be in early 2018.

    All the very best

    Mike
     
  3. Graham Patterson

    Graham Patterson Member

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    If there is a 'standard' for 5x4 camera boards, it is the Linhof/Wista type. There are historical reasons why Linhof boards have the odd cutouts, but if you are looking at a field camera you could ignore most except the overall dimensions. The light trap ring on the inside is nice to have, but a felt surface will also work. These boards often have offset holes, again due to the early Linhof design not allowing for fall, so it was built-in. A central hole will work fine with most wood cameras.

    Copal 0 or Copal 1 shutters are an easy fit in these boards, but Copal 3 starts to get difficult. The lens opening behind the board can limit the size of the lens you can mount easily. My Wista will take my 90mm f5.6 rear element through its circular aperture easily. My MPP with a square opening - no.

    With 5x4 he lens board is partly controlled by the amount of bellows taper used to get the camera to fold small. A bigger board and there is less room to taper, so the compressed bellows is thicker. This is a big problem if you want to go beyond double extension (twice the standard focal length).

    On 8x10, the nearest thing to a standard board is the Sinar. This has some complicated rims on the back, but a lot of cameras can cope with the variation. An adapter board to allow smaller mounted lenses to be used is a good plan. Sinar to Wista adapters are popular with people running both formats.

    When I built my first 8x10 I made it able to take the Wista and MPP boards as that is what I had. I actually have different retainers because the MPP board is thicker than the Wista type.

    8x10 format lenses tend to be heavier. A kilo is not unusual.

    Film holders up to 8x10 are pretty standard. It is not that difficult to get a focus screen in register. I built my 8x10 with a removable screen rather than a full spring back. That way I just had to duplicate the film holder dimensions. I wouldn't do that for a more commercially aimed item.

    One thing that is not always obvious until one has some hours using a large format camera is that the importance of certain features varies a lot with the photographer and their subjects. With 8x10, rear movements can be really useful because of the extension of the camera, as can rear focusing. Some people will want lots of rise, others lots of tilt. The amount of slop in the camera can be important to some. Ideally everything should lock down tight, and making a single adjustment should not risk changing another setting.

    My MPP is really solid, but the price is a heavier metal camera compared to the wooden Wista. My 8x10 is a monorail. It works, with limitations, and has proven enough to let me try the larger format without a huge investment.

    Graham
     
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  4. Michael Diblicek

    Michael Diblicek New Member

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    Hi Graham,

    Many thanks for all the info, much appreciated. Sorry for the delay in getting back.

    As you've already built a LF camera, can you tell me, is the ground glass larger than the actual 10x8 (5x4) size and does this matter.

    For example i place my 10x8 film holder in the film holder, remove the dark slide, so should the ground glass cover ONLY the 10x8 (5x4) size, or can it bit a bit larger?? and does it make any difference.

    Many thanks

    All the best

    Mike
     
  5. Graham Patterson

    Graham Patterson Member

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    The ground glass view has to be in exactly the same plane as the film when the film holder is loaded. In practice there is a small edge loss on the film due to the way the film holder grips the edge of the film.

    It would be unusual to have a ground glass view significantly larger than the film - it would make accurate composition difficult. Now the actual _glass_ will have to be a bit larger, but the frame facing the lens will be the film size. This is because you need a ledge to rest the glass on at the correct register. On the last one I made the glass (actually acrylic) was about a quarter inch larger than the lens side of the frame so I had an overlap to clamp it against. I used some brass sheet I bent to make springs.

    When used on the camera you only see the film area illuminated.
     
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  6. David M

    David M Member

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    Yes, Graham is right.
    The ground surface of the ground glass should be in the same plane as the film will be when the holder is inserted. This ground surface is almost always placed on the inside surface, facing the lens and (if used) a fresnel lens is on the viewer's side. The grooves in the fresnel are usually placed so they face the lens and the smooth side faces the viewer. Sometimes a second sheet of glass might be placed on the viewer's side of the fresnel to protect it from scratches.
    If a fresnel lens is placed on the lens side of the glass, its effect on the image-forming light path will have to be calculated and compensated for, as it changes to point of focus. This will need some theoretical optical calculations.
    Photographers are divided on the value of a fresnel; some prefer the improved brightness and others find the grooves make fine focus difficult. The fresnel works by redirecting the diffused light from the ground glass towards the photographer's eye; it doesn't amplify the light. Different focal lengths can be used for very long or short lenses.
    In the literature on ground glass, I have found the terms front and back are used confusingly. "Front" sometimes means the front of the camera, and sometimes the side facing the photographer. I hope "lens" and "viewer" are clear.
    The actual piece of glass may be any convenient size, but the visible opening in the frame should coincide with the exposed area of the film holder. That is, the area between the rails, not the opening in which the darkslide (sheath) fits.
    If a roll-film back is used, the appropriate areas might be shown, or a grid drawn to aid alignment. Other markings are possible. For instance, it might be useful for a portrait photographer to mark the preferred position of a sitter's head. If the back has swing or tilt, the axes of rotation may be marked, as with Sinar.
    Opinions vary on the value of cut-off corners.
    Opinions also vary on the optimum grind. Very broadly, a coarser grind gives a brighter image, but a finer grind shows more detail for precise focus.
    Grinding glass is another subject.
     
    Last edited: Apr 6, 2017
  7. David M

    David M Member

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    I've been shooting my mouth off about camera-making.
    It seemed only fair show one of my efforts. This is a 10x8 camera, constructed from MDF as a prototype for some more durable material. Although there are imperfections, it works well enough to let me put off making the "real" one.. Front: rise, fall, shift, axial tilt. Rear: Swing, base tilt, shift, no rise. It taught me that I prefer 5x4.


    IMG_1197.jpg
     
    Last edited: Apr 8, 2017
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  8. Michael Diblicek

    Michael Diblicek New Member

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    Many thanks for that David,

    This was a really great piece of info concerning the glass, and if i understand correctly it's the ground/interior side that has to be on the exact same plane as the film in the holder.

    I have found someone who will be calculating this with a laser measuring instrument, which is a bonus. :), and thanks for the glass size response. :)

    All the best

    Mike
     
  9. Michael Diblicek

    Michael Diblicek New Member

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    That's a great piece of work David.
    A big congrats.
    All the essentials, what more could you ask for. Amazing.

    Mike
     
  10. David M

    David M Member

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    I'm wondering if it might be sensible to invest in a vernier caliper. A digital version is easier to read and it will measure with an accuracy of a hundredth of a millimetre. (0.01mm – FP4 is 0.18mm thick.) It will measure length, naturally, but also thickness, inside and outside diameters and depth. Remarkably cheap, too at about £20 on (e.g.) Amazon. There may be other tool shops that are more convenient for you.
     
    Last edited: Apr 7, 2017
  11. Graham Patterson

    Graham Patterson Member

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    I don't see how this sort of thing can be done without a good set of calipers - at least for things like film/focus registration measurements. Apart from that, most large format adjustments are made by visual inspection, and precision is not quite as critical.

    My 8x10 was done using largely hand tools and clamps . No drill press or table saw, and it is crude. But it works well enough to let me play with 8x10 and decide if I want to use the format more. I think if Intrepid brings their 8x10 to market I might invest in one.
     
  12. David M

    David M Member

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    Mine was made on the kitchen table with fairly simple tools. Some parts had to be made and re-made several times, but MDF is easy to work. I looked at making the bellows myself, and was searching for the ideal thin, tough, flexible and opaque material when a set of very cheap 10x8 Sinar bellows came up on eBay... One day I shall make my own. It looks fiddly and tedious, but quite possible.
    I do agree that, once the camera is made, using an LF camera is largely pragmatic. You focus; you look; you focus again... If it looks right, it is right.
    I have one of the Mark 1 5x4 Intrepid cameras, which I bought out of curiosity and because I thought they deserved support. It's adequately made, very light and works well. I haven't handled the Mark 2. I'm waiting for their 10x8, like you.
     

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