Compur Shutters flange to Film distance

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sebastianz

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Hello guys. I have technical questions regarding the flange to film distance or shutters in general. What does affect the different shutter sizes in the case of compur/copal? i.e. If I have a 90mm f8 with a #00 shutter the flange to film distance is the same as if I have a 90mm f8 with a #0 shutter?

thanks, and apologies if this question offended the most advanced photographers.
 

abruzzi

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the flange to film distance is specific to a lens design, so a 90mm angulon, a 90mm super angulon, and a 90mm grandagon will all have slightly different FFD.
 

BradS

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The flange to film distance is determined by the focus motion of the camera and the bellows, not the shutter. You change the flange to film distance when you rotate the focus which changes the length of the bellows....the shutter has nothing to do with it.

I'm not sure that I understand what you are asking. What is the problem you're trying to solve? What is it you want to do?
 

DREW WILEY

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90 mm is the nominal focal length listed for marketing purposes. The exact focal length has to be looked up on the spec sheet for that particular series. And you haven't told us exactly which 90mm lens you have in mind.
 
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sebastianz

sebastianz

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Thanks for the reply @BradS and @DREW WILEY. What I'm trying to do is to make a DIY 6x17 camera focused at infinity. I scout in some Schneider lenses, and the FFD all of them are based in a #0 shutter. The lens I have is a Schneider 90mm f8 super angulon Compur #00.

So what I'm trying to solve here is the FFD. Sorry about the confusion.
 

reddesert

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The flange to film distance can depend on both the lens and the shutter it is mounted in. That is, different 90mm lenses (like Schneider 90/8 vs Fuji 90/8) may have a principal plane in different locations relative to the threads that screw into the shutter. But also, if you have a Schneider 90/8 in a Compur #00, it has to have different lens cells than a Schneider 90/8 in a Compur #0. Because the thread sizes are different between the two shutters, and critically, the #00 is 16mm thick while the #0 is 20mm thick. (These numbers are all available in tables on the web.) Thus, FFD numbers for a lens in #00 will likely be within a few mm of the numbers in #0 shutter, but not the same.

The thing is, the FFD is not particularly interesting for bellows cameras and so you can't count on finding reliable numbers for it. You have the lens. Just measure the FFD yourself. You will need some way of holding the lens and a ground glass (a 4x5 bellows camera would work). You're going to need those anyway to refine the design of your camera.
 

Dan Fromm

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Hmm. The OP has in mind to make a 6x17 camera that will use a 90/8 Super Angulon. In this discussion https://www.photrio.com/forum/threa...on-90mm-f8-retainer-ring.199756/#post-2696366 I gave him directions to the Schneider data sheets that have what he wants to know. I don't know why he didn't follow them.

YP, the Kolve list that you gave a link to is well and good but it ignores variation. The FFDs it gives are good starting points for people who want to know roughly where a lens should sit when focused to infinity but that's all they are.
 

Ian C

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If I understand correctly, you’re making a simple 6 x 17 cm fixed-focus camera with a wide-angle lens. If so, I think you’re making a mistake in setting the focus to infinity. It’s more practical to set the focus to the hyperfocal distance at the most useful aperture.

You need to set the aperture and alter the shutter time to accommodate the exposure. This will vary depending on the film speed, light meter reading, and whatever filter is in use.

Here is a data sheet for the Schneider Super Angulon lenses dated 11/76. It lists slightly different flange distances for the 8/90 Super Angulon mounted in each of 4 different shutters (as well as in a barrel mount). The flange distance given for this lens in the Compur 0 shutter is given as 99.4 mm. Unfortunately, the flange distance for the 8/90 Super Angulon mounted in the Compur 00 shutter is not given.

https://www.pacificrimcamera.com/rl/02156/02156.pdf

After determining the fixed aperture at which you’ll use the lens, compute the hyperfocal distance using the online DOF program DOF Master.

https://www.dofmaster.com/dofjs.html

For example, suppose that you choose f/45 for maximum depth of field. That gives a hyperfocal distance of H = 1890 mm, or 1.89 meters. Then everything from H/2 = 945 mm, or 0.95 meters to infinity will be acceptably resolved using a circle of confusion diameter of 0.10 mm. Of course, you can recompute this with a smaller COC if you prefer a tighter standard.

You can perform calculations for the placement of the lens relative to the film plane. A simpler solution requires no arithmetic.

If you have, or can borrow, a view camera on which to temporarily mount the lens and shutter, it’s a simple matter to set a focusing target at the hyperfocal distance H, focus upon it, lock the focus, and measure the distance from the front to the lens board to the ground glass. This is the distance that must be duplicated on your 6 x 17 cm fixed focus camera to obtain the same focus with the same lens & shutter on your project camera.

A safe procedure to measure the distance from the front of the lens board to the front of the ground glass is to use a small diameter (say 8 mm) wooden dowel. Insert the dowel through the lens hole of a lens board mounted in the camera until the end lightly touches the ground glass. Mark the dowel where it passes through the front of the board with a sharp pencil.

If you use a small aperture, such as f/45 with a 90 mm lens, the depth of field is generous, so a small error in positioning the lens won’t be noticed in the resulting photo.
 
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sebastianz

sebastianz

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Huge thanks to everyone; it was really helpful with all the information. Yes, I will focus on the hyperfocal distance. I will have to design a temporal view camera for that. Thank you all!

@TheYoungPretender Great link!
@reddesert, that's the technical data that was needed! awesome
@Ian C I came across that list, but I will follow that workflow.

thank you all!
 

pdccamerqs

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I agree, don't set to Infinity, choose the Hyperfocal distance for f11 or f16.

Ian

Ian C and Ian G. If the OP was mounting his lens in a helical focus mount or on a bellows camera (eg. 2x3 baby graphic) would you suggest to set the lens at infinity focus to start and then mark the focus positions for hyperlocal at f/11, f/16, f/22, etc. ?

Best,

Paul
 

blee1996

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I have a similar setup, Kraken 617 with 90/8 Fujinon lens, albeit with focusing helicoid. With large format, it is better to have a bit of focus control since the DoF is not that forgiving. And those M65 focus helicoid is easy to buy.

Kraken 617 panoramic camera - front view by Zheng, on Flickr

And here is the DoF table I stick to the back of my camera:

Screenshot 2023-07-16 at 7.39.36 PM.png
 
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sebastianz

sebastianz

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Hey guys do you know which helicoid focusing adapter I need for a 90mm f8? I have investigated and they recommend the M65, but then I have to design a base plate for mounting in to the cone.
 

OAPOli

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I've used M65 hardware for #0 and #1 shutters. You can buy the flange mount, helicoid and shutter to m65 adapter. Unfortunately it seems #00 to m65 doesn't exist. You could make a simple circular lens board and glue it to a #0-M65 adapter.

(Edit: RAF makes a plain 26.3mm bore m65 adapter)

M42 is also an option. I've 3D printed a lens board with a hole for a #00 shutter and m42 thread. You could also just make a circular board and glue a M39-M42 adapter on it. M42 flanges are harder to buy (I've used some from M42 mirrorless adapters), but you could recycle one from a camera body.

Once you have the lens on a helicoid it is easier to find the flange-focus distance. You can mount the lens on a digital camera and find infinity. Or if you have a ballpark estimate you can make a prototype that is a bit short and fine-tune via ground glass.

The spec sheets are a good start but your lens might vary a bit. My Xenotar had a 1mm shorter FFD (in line with 1-2% variation in focal length from nominal).
 
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sebastianz

sebastianz

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Hello Guys, questions here about the cone, I reduced the size of the cone, but I'm not sure if this design criteria it is ok?
 

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