DIY 4x5 Pinhole Math...

[ChristopherCoy]

but really, Pythagorean formula for a right triangle is easy enough they teach it in fourth grade (or did when I was that age).

I guess I should clarify so I don't sound like a total bafoon, like always.

I can get the basic shapes figured out fairly easily. It's the compound mitered angles that I have issues with.

 

[ChristopherCoy]

I've gotten my design this far, and it's to the mm. The back of the lens board is exactly 156mm from the film plane. Might not be as accurate once I put saw to wood. I used measurements from this thread and built the film holder first. And then built around it. I'm thinking materials will be 1/4" birch ply. I wish I could figure out how to attach the front to the back with bellows so that it's collapsable.

 

[ChristopherCoy]

I think I'm going to use some matboard pieces and do this for bellows.

 

[MattKing]

Remember to include a convenient form of "shutter", a tripod socket (or two - one for each of vertical and horizontal) and some means of framing the scene.

 

[grat]

Got a smart phone? Download a calculator app (I use one that emulates an HP-41CX). Squares and square roots are all that's needed, but few non-scientific calculators make both easy.

Or you could type it into the search bar for google or duckduckgo:

=(4^2+5^2)^.5

 

[Grandpa Ron]

Not to rain on anybody's parade; though it is pretty well agreed that there is an optimal pin hole size for each aperture f number, what that number is varies with who is developing the formula. Almost all pinhole formulas round off, estimate or ignore some of the variables.

I have had good luck with the calculator given above, I would recommend it for anyone.

Everyone wants a pinhole small enough to produce a sharper image, yet large enough to not introduce diffraction issues.I am working with a 4x5 view camera with 9 inches of bellow length. Theoretically I could match almost any pinhole to film plane calculation.

However, once you realize that a pinhole photo will never be as sharp as a lens, trying to judge between two very nice pinhole photos, which exposure is less sharp can start to become difficult.

As mentioned working with a larger format is an advantage. some of the nicest pinhole photos I have seen were 8"x10" format.

 

[Donald Qualls]

@ChristopherCoy Unless you have a limitation on the dimensions of your wood, it would surely be simpler to make a plain box rather than that "square cone" shape. That way, all your wood pieces are rectangles (with rabbet joints, lap joints, or whatever) and all your join angles are right angles.

I'll admit, even though I started to learn trigonometry in 8th grade (1972, via slide rule), when you start to get angles in three dimensions the trig can get complex enough to make it a PITA.

 

[ChristopherCoy]

...when you start to get angles in three dimensions the trig can get complex enough to make it a PITA.

I know. But you know how parents tell their kids “quit being so hard headed”?

I never listened.

I think I’ve got a plan for a collapsible bellows 4x5. I can’t explain how I’m going to do it, but I have a very clear idea.

 

[Donald Qualls]

Okay, reinventing the wheel is legit for a hobby.

You'll need some way to slide the front standard back into the body or detach the lens board from the standard in order to have the camera fold. Might be able to detach the bellows and fold the standard down onto the bed (as it seems you're planning, based on the drawing) -- that would cause problems with a lens, but might be okay for a manual-shutter pinhole.

 

[Michael Teresko]

I guess I should clarify so I don't sound like a total bafoon, like always.

I can get the basic shapes figured out fairly easily. It's the compound mitered angles that I have issues with.

https://www.wwgofga.com/compound-miter-calculator/

There are lots of these online. This one is pretty simple.

 

[ChristopherCoy]

https://www.wwgofga.com/compound-miter-calculator/

There are lots of these online. This one is pretty simple.

Oh wow! Thanks for that!!

 

[Grandpa Ron]

As and incessant diddler I understand that hand-making projects is extremely rewarding. I have built muzzle loaders, electronic gear, musical instruments and etc.

However, I have discovered that when working in a new endeavor, it is often better to proto-type it, rather than jump to the completed project.

I can almost guarantee that once you start using your pinhole camera you will wish to try other pinholes, focal lengths, film sizes and etc. simply put; my suggestion is to make it as adjustable as possible. Once you know what you like, then you can complete the fine art master piece.

Good Luck.

 

[Jim Jones]

Learn the fundamentals of pinhole photography well before designing the cameras. The most versatile camera for learning pinhole photography may be a fairly short frame that will take a film holder on the back and a large lens board on the front. A large lens board can be made with an extension if you really want to try telephoto pinhole photography. However, wide angle pinhole photography is much better. Once I used a 24 foot long pinhole camera to photograph an eclipse. It wasn't easy to use, and the images were not sharp, even with an ideally sized pinhole.
Non-enlarged wide angle 4x5 pinhole images can look sharp at arm's length. This will depend on a properly sized pinhole for the desired focal length. Yes, for any focal length, pinholes do have an optimum diameter. Deviating from this by 10% causes perceptible loss of sharpness. However, one might try a somewhat larger diameter to enhance the fall-off in sharpness in image corners that occurs with wide angle pinholes.
I make it sound complicated, but even pinhole photography can be complicated for one seeking the best performance. Eric Renner spent many decades studying and practicing pinhole photography. His Pinhole Photography: Rediscovering a Historic Technique is the most comprehensive single source pf published information with which I am familiar. Some of the information that later appeared in that book plus a rich variety of images were also available in the Pinhole Journal which he also published for perhaps 10 years. An online source of good information is https://jongrepstad.com/