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I hope to make a low budget 8x10 large format camera.

Lenses are expensive. So will a small format lens focus on the relatively distant image plane within an 8x10? I have just bought a Soviet large format lens at a good price but was lucky. Unfortunately it does not have a shutter and copal shutters sold separately are expensive.

If I could buy a SMENA lens designed for a smaller LOMO, the experiment might be cost effective.

Many thanks

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Focus is not the issue here. The issue is coverage.

Any lens gathers light from a cone in front of it (angle depending on the focal length), and projects it to a cone behind it (angle depending on coverage). So long as the lens is far enough away from the film plane, there exists some plane in the real world that will be focused on the film plane.

But...in the case of your SMEMA lens, designed for 35mm format photography, focused at infinity, the projection cone will end up covering approximately a 22mm radius circle. To cover the full 8x10 format, you would need coverage of at least 180mm (both calcs, see Pythagoras).

Also, being a 40mm lens, the lens would have to be placed 40mm (approx, from focal centre point) from the film plane. If you look at how your camera is setup, you'll see that it is expecting lenses to be mounted approximately 200mm away.

You could mount the lens further away, and as the light projected is a cone, it would cover more of the film. Huzzah! Oh, but that would then mean the focus getting closer and closer into the extreme macro. Napkin calculations. at 400mm extension the lens would have enough coverage. At that distance, the magnification ratio would be about 10:1, and the focal distance might be closer than the design of the lens would allow. Oh, and you'd need to dial in 7 stops of exposure compensation at that extension (more coverage implies less light per unit area), so good luck focusing on the ground glass.

No shortcuts here, I'm afraid. Larger format cameras require lenses with sufficient coverage. Yes, copal shutters at this size are expensive. For a cheaper alternative you could use in conjunction with your Soviet glass, trying searching for a 'Thornton Pickard' shutter that can be situated behind the lens.

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  • Thank you psion5mx. Your explanation of the geometry is very helpful. Thanks also for the Thornton Pickard shutter recommendation.
    – JanUts
    Feb 26 '20 at 8:52
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The camera lens projects an image of the outside world on the surface of photographic film or digital sensor. The focal length of this lens is a measurement taken, lens-to-image, when the lens is focused on a far distant object (like a star). The focal length defines how big images of objects will be. The longer the focal length, the bigger they image.

All lenses project a circular image, however only the center portion s image is suitable for pictorial photography. The center portion is called the “circle of good definition”. Outside these limits the projected image is substandard, being too dim and blurred.

As a rule-of-thumb we fit cameras with a lens that has a focal length about equal to the corner-to-corner measure of the format. An 8x0 inch large format camera has a diagonal measure of 12.8 inches = 325mm. Such a lash-up is more likely to produce a circle of good definition with sufficient diameter to cover the frame without a noticeable vignette.

Can a lens intended to be mounted on miniature cameras work on a gross format camera? It may be possible to mount and focus short focal length lenses provide the bellows mechanism will allow the lens to be positioned sufficiently close to the film plane (dubious). If such a short lens will focus, it’s circle of good definition will only cover only 30% or less of 8x10’s area.

A lens with a focal length about equal to the diagonal of a format is termed “normal”. Lenses about 70% of “normal” or shorter are labeled wide-angle. Suitable wide-angle lenses are crafted to have an expanded circle of good definition.

Your idea to mount miniature camera lenses on an 8x10 format camera is likely to fail.

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  • Thank you Alan. I appreciate your explanation of the 12.8”/325mm diagonal in relation to focal length. Your explanation of the circle of good definition is also helpful, when I think of examples of old photos.
    – JanUts
    Feb 26 '20 at 9:00
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Experimental lenses that can be upcycled into this kind of application are more likely found in junked projection gear (eg overhead projectors, epidiascopes, old school video projectors, rear projection TVs) than in any cheap kind of camera, so keep your eyes open regarding that kind of opportunity.

Some very old school, simple SLR long focus lenses (that only consist of a front group and a lot of tube) might be adaptable to that application too.

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  • Thank you rackandboneman, for providing other upcycling possibilities. Your suggestion of flee markets is helpful.
    – JanUts
    Feb 26 '20 at 21:00
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Your question, as asked, is possibly tackling your problem from the wrong side.

You want a large format camera, you have a large format lens, your large format lens has no shutter, modern large format shutters are expensive...

  • Can I use a small format lens and its shutter on my large format camera?

This line of thinking has skipped over the more direct question:

  • What are inexpensive shutter solutions for large format lenses?

Guillotine shutters can be made easily, and are a great project if you're already building a camera in general. Especially if you're a fan of physics. [And who isn't a fan of physics?]

If you're familiar with simple electronics, or willing to learn, then a small electronically timed shutter is not an excessively difficult project. Scratch built is an option, or salvaging components from an otherwise dead clockwork shutter.

Keeping an eye out for cheap mechanical shutters that may need minimal work is also an option.

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  • Thank you TL for cutting to the chase. You are quite correct about having a lens and needing a shutter. I’ll certainly investigate means of making a shutter. It is possible that I’ll want a variety of lenses for use on the camera but I’m yet to determine that. Thanks again JU.
    – JanUts
    Feb 27 '20 at 20:24

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