What's your pinhole Angle of View?

[Dr Croubie]

Hi all. In designing my suitcase-camera for WPPD (it's practically done, but another can of black spraypaint would be nice) I've looked at fsm knows how many different pinhole calculators, and giving different coverage figures (at least, for the ones that do at all).

The vitalstatistix of my suitcase is f=20cm (give or take), ø=600µm (from Skink Pinhole), f/333 (give or take).
Mr Pinhole says that this will cover 384mm, which isn't much bigger than 8x10".
Photostuff says I'll cover 26cm, which is only a bit more than 5x7".
Only DIYphotography is sensible and talks about the geometry using the thickness of the plate (which I can't exactly measure without a good micrometer).

(Not to mention that with the various different calculators I'm getting anywhere from 0.4mm to 0.7mm optimum pinhole size, depending on whatever Magic Number they've used, I just stabbed in the middle and bought a 0.6mm).

But anyway, I'd rather get some ideas of others' experiences as to what a decent angle of view is so I can figure out how big I can put in this thing (obviously I could just buy the biggest that'd fit and see, but big paper is expensive and not too common around here, and I don't want to waste too much of my 20x24" Kodalith cutting it up).
I know that things like sharpness and especially cos4 vignetting and where those two produce 'maximum' IC is going to be a bit subjective, so just looking for a bit of a rough guide from others' experiences...

 

[Dr Croubie]

ps, I've just measured the inside of the case, I can probably fit 40x60cm (15x23") in there at a stretch. But that's an image circle of 72cm, to cover that needs 120 degrees at f=20cm.
So I doubt I'm getting that close.
A more reasonable 8x12" is 20x30cm, needing 83 degrees (ie, 1/4 of a sheet of my kodalith). Can I push a regular pinhole that wide?
Or just settle on 8x10 and I can start using the MGiv I've got, is 77 degrees doable?

 

[DWThomas]

In my (limited) experience, Mr. Pinhole is very pessimistic on the coverage issue. According to him my last two cameras don't work!

The problem is fall-off away from the center, and yes, it does happen, it's inevitable, but Mr. Pinhole does not specify the criteria he uses; at least I've not found it. My own most recent cameras are a 4x5 with about 103º diagonal field of view and an 8x10 with 92º.

Additional items such as a thick pinhole plate can compound the fall-off problem as well.

When it doubt, try it and see!

 

[Jim Noel]

Put the largest piece of light sensitive material you wish in the camera and try it out. Yes, there will likely be fall-off but so what? The purpose of a pinhole camera is not to compete with the totally sharp edge to edge image produced by an over priced lens. Sometimes the fall-off enhances the image.

 

[RalphLambrecht]

I recorded all my experience with pinholes in the attached article.

 

[SMBooth]

Why not just tape a 50mm strip from the centre out to one corner and see the fall off you get. Save using a whole sheet. Just use a piece of paper and tape two together to get the length you need.

 

[NedL]

I don't know what formulas the various pinhole programs use to estimate coverage. My 8x10 pinhole camera has a "focal" length of 5 inches (~127 mm ), so the angle is 90 degrees in the 10" direction. There is some falloff but there is image all the way to the corners, even with paper negatives which have more limited range. So I'd guess you could go up to about 16" and get results similar to mine. You can look at some here and see if you think there is too much falloff. Maybe ignore the first one, "riverspan", since it was shot in failing sunset light.

http://www.ipernity.com/doc/295785/album/353855

 

[Jim Jones]

Dr. C.: For your suitcase, I'd make a pinhole about .5mm in diameter, and use a sheet of paper that nearly fills the back side of the suitcase. Crop the image to suit your own preference. 90 degrees coverage is no strain for a properly made pinhole. The vignetting from greater coverage is pleasing to some pinhole photographers.

 

[pgomena]

I remember reading somewhere that the image circle is roughly 3.5 x focal length.