Hey all, I'm wanting to design my own large format medium camera, and while I'm researching what sized film/paper I want to work with, I've been trying to find the formulas to calculate what focal length I need for a given film size, and the pinhole diameter and depth for full exposure and to create a specific angle of view. Can anyone help me out with a resource for this?
Designing a pinhole camera: Dimensions?
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I've found http://www.mrpinhole.com/calcpinh.php to be useful.
A Windows based program, Pinhole Designer (that has not been updated in over a decade).
Mr Pinhole runs via web scripts, so works via a browser on just about any platform.
I lean away from Mr Pinhole because in any of these exercises there are some options that could be selected and Mr P seems not to provide handles to change them nor does it tell what it uses -- at least I've not found them.
There is a library of resources on the Worldwide Pinhole Photography Day site.
Some of my efforts are found in my PBase galleries. I've done 4x5 and 8x10.
So there's a few!
Mr Pinhole runs via web scripts, so works via a browser on just about any platform.
I lean away from Mr Pinhole because in any of these exercises there are some options that could be selected and Mr P seems not to provide handles to change them nor does it tell what it uses -- at least I've not found them.
There is a library of resources on the Worldwide Pinhole Photography Day site.
Some of my efforts are found in my PBase galleries. I've done 4x5 and 8x10.
So there's a few!
Two basic ways to do large format pinhole photography: use standard film holders, or set it up to use photo paper only (load/unload under safelight).
If you use film holders, you must design the back of the camera to light seal on the film holder, and retain it at least during the exposure (seconds to hours, depending on the film, pinhole aperture, focal length, and light). It's easy enough to take dimensions from a film holder, so start by getting at least one of those, if you plan to go that way. Critical is the groove to accommodate the rib on the film holders; that's both part of the light sealing and a mechanical retention feature.
If you'll darkroom or changing bag load for single exposures, it's probably best to size to fit standard precut photo paper (5x7 or 8x10, for instance) which, in the USA, is commonly cut to full inch dimension (cut film is a couple millimeters undersize both directions, a legacy of the transition from glass plates to film in sheaths to fit in glass plate holders). A slip-in retainer is pretty easy to fabricate from poster board or foam core, or you can design the camera to closing it retains the paper (or film).
Pinhole cameras are often designed to range from fairly wide (say, 90 mm on 4x5) to insanely wide (40 mm on 4x5?) angle of view -- including use of curved paper to give angles of view approaching 180 degrees, or (like one I built) film wrapped inside a cylindrical body with the pinhole in the end, for a 360 degree anamorphic panorama effect. The preference for wide angles is partly because it's extra work to make a viewfinder, and wide angle covers a multitude of aiming errors, and partly because images will tend to be sharper with an optimal hole size for short projection distance, than with an optimum hole for a longer distance (which will be larger).
One thing to be aware of -- with a very short projection distance on flat film or paper, you'll get a significant change in the projection distance and effective f-ratio from the center, directly behind the hole, to the edges or corners of the image plane. This produces a very characteristic vignetting effect, but also requires a compromise in hole size, between optimum for the center (smaller) and optimum for the corners (bigger), as well as requiring that you compromise exposure. The wider your field of view (=> shorter projection distance) the larger this difference will be. If it's too big, there will be a very strong darkening of the corners of the image, as well as a loss of sharpness at the center and corners due to less optimum hole to distance ratios and off-round apparent hole shape due to perspective.
Generally, though, you won't need to worry about most of this for your first pinhole camera design (or perhaps your first dozen). Pick a standard film or paper size, a "focal length" you think you'll find interesting, build your camera, drill your hole, and make some images to see what you like -- then make the next one better.
If you use film holders, you must design the back of the camera to light seal on the film holder, and retain it at least during the exposure (seconds to hours, depending on the film, pinhole aperture, focal length, and light). It's easy enough to take dimensions from a film holder, so start by getting at least one of those, if you plan to go that way. Critical is the groove to accommodate the rib on the film holders; that's both part of the light sealing and a mechanical retention feature.
If you'll darkroom or changing bag load for single exposures, it's probably best to size to fit standard precut photo paper (5x7 or 8x10, for instance) which, in the USA, is commonly cut to full inch dimension (cut film is a couple millimeters undersize both directions, a legacy of the transition from glass plates to film in sheaths to fit in glass plate holders). A slip-in retainer is pretty easy to fabricate from poster board or foam core, or you can design the camera to closing it retains the paper (or film).
Pinhole cameras are often designed to range from fairly wide (say, 90 mm on 4x5) to insanely wide (40 mm on 4x5?) angle of view -- including use of curved paper to give angles of view approaching 180 degrees, or (like one I built) film wrapped inside a cylindrical body with the pinhole in the end, for a 360 degree anamorphic panorama effect. The preference for wide angles is partly because it's extra work to make a viewfinder, and wide angle covers a multitude of aiming errors, and partly because images will tend to be sharper with an optimal hole size for short projection distance, than with an optimum hole for a longer distance (which will be larger).
One thing to be aware of -- with a very short projection distance on flat film or paper, you'll get a significant change in the projection distance and effective f-ratio from the center, directly behind the hole, to the edges or corners of the image plane. This produces a very characteristic vignetting effect, but also requires a compromise in hole size, between optimum for the center (smaller) and optimum for the corners (bigger), as well as requiring that you compromise exposure. The wider your field of view (=> shorter projection distance) the larger this difference will be. If it's too big, there will be a very strong darkening of the corners of the image, as well as a loss of sharpness at the center and corners due to less optimum hole to distance ratios and off-round apparent hole shape due to perspective.
Generally, though, you won't need to worry about most of this for your first pinhole camera design (or perhaps your first dozen). Pick a standard film or paper size, a "focal length" you think you'll find interesting, build your camera, drill your hole, and make some images to see what you like -- then make the next one better.
The maximum and minimum focal length formulas for a pinhole are somewhat complicated. The maximum focal length would be limited by diffraction. The Airy disk size that would produce no recognizable image is related to the viewing distance of the final print. So there are a lot of "it depends on this and that" variables. In simpler terms the focal length can be pretty much as long as your bellows maximum extension.
The minimum focal length for rectilinear imaging is related to the light striking the film at an acute angle. This can be quantified with Lambert's Law, but in real life you would need to do some experimentation if you want the full frame exposed due to somewhat unpredictable reciprocity characteristics of light sensitive media.
The minimum focal length for rectilinear imaging is related to the light striking the film at an acute angle. This can be quantified with Lambert's Law, but in real life you would need to do some experimentation if you want the full frame exposed due to somewhat unpredictable reciprocity characteristics of light sensitive media.
Exactly what is a "large format medium camera?"
Just kidding. I needed a little levity in the times we live.
There must be an equivalent diagram for cameras?
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Does a Mamiya C series TLR or RB67 count? Or is that just a large medium format camera?
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