f400 pinhole 8 mins exposure on a dull day
Taken with a 0.4 mm pinhole giving f400. It was very dull day. After working out the exposure, had to treble for reciprocity...total 8 mins of sitting around.
Used a Linhof 4x5 and TMax 100. Lost a bit rephotographing the neg on a lightbox, but the tones are nice on the original. Notice all is "sharp" throughout the depth of field.
Pinholes are heaps of fun, not the least is the ability to have a cup of coffee while the exposure is being made! I see that you have dabbled in the realm of spirit photography at the same time, not bad with a pinhole!
A real nice shot.
Forgive me but what focal length do you get from a 0.4mm hole on 4x5" and how do you focus ???
I am clompletely new to pinholes......
Peter, there is no focusing a pinhole camera. Depth of field is, well, just about truly infinite. The problem because there is no view finder can be pointing the camera in the right direction. This easily solved with practice and some tricks of the trade. If you are really interested I's suggest you stop by f295.org. There is a wealth of information there and a lot of helpful and dedicated pinholers.
I'm going to estimate 160mm focal length based on f/stop and pinhole diameter. How close did I come David?
Mary, you've certainly used the right formula ie focal length=f stop multiplied by lens aperture (in this case pinhole diameter, 0.4mm).
that is, 160=400 times 0.4. As said there is no focus, but there is a best distance for optimum quality and film coverage.
In practice it was a little shorter, around135mm, because I used a lens to look at composition on the Linhof ground glass screen. Then just substituted a pinhole lens panel, and slipped in a film holder. Then sat back with a glass of mulled wine...you can't see the wine glass, it had too much movement!
I used a a soft drink (soda) can aluminium, and punched a hole with a dressmakers needle, blackened hole with felt pen. Look you can do this stuff with a shoe box. The ambient original light reading was F8@1/15 sec, 100 iso film, very flat day. Did the time calculations from there..as said 8 minutes!
The Holgas, and Lomos are out there, but a sh...load more fun doing it yourself from first principles.
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Marv not Mary...
Sorry, that's Marv. I didn't think you looked like a Mary, but there are some odd avitars around!
What have you been doing with large format pinholes Marv??
There is a nice little program called Pinhole Designer.
It calculates F stop from diameter of needle / hole.
Ideal focal length for a given needle / hole diameter.
Plus an exposure guide - that includes reciprocity failure calculations for many films.
Numnutz, thats a great resource, thanks.