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Re: [OM] pinhole OM

Subject: Re: [OM] pinhole OM
From: "imagineero ." <imagineero@xxxxxxxxxxx>
Date: Thu, 28 Oct 1999 09:12:33 PDT
In a message dated 10/27/99 8:41:28 PM Eastern Daylight Time,
wright@xxxxxxxxxxxx writes:

> OK folks, I have a special pinhole for my OM-2n. It's made from a body cap, > where the center was drilled out and a pinhole plate was glued in place. It > is supposedly 50mm f/185. Obviously, there is no aperture connector to the > body or meter in the camera. So, I tried setting the film speed to 400, the > switch to auto, and cocked the shutter and released it. The shutter opened, > stayed open for about a minute, then closed. Was this an acurate exposure? > Can I rely on this camera to give correct exposures or do I have go to my
>  pinhole charts? Any help is appreciated.

Theoretically you should get a good exposure. An OM-2n, when metering in auto
mode, doesn't care what the actual aperture is. It just measures the light
reaching the film and integrates it over time. An exposure that long probably will require adjustment for reciprocity failure. How much will depend on what
kind of film you are using. I presume you had film in the camera for this
test? If not, then the results won't be indicative of the true exposure,
since the meter is reading off of the black pressure plate and not the film.

BTW, where did you get the pinhole plate? Or did you make it? I have a box
full of body caps I might want to try this with. A lot of the third party
ones are nice and flat (unlike the OEM Oly's) which should be easier to mount
the pinhole on.

Good luck, and I'd love to see your results!

Paul Schings

It is possible to make pinhole plates yourself, though they're not very good. There is always difraction caused by the hole not being perfect. The best one's seem to be made by lasers on ultra thin plates. There was a guy on the web selling them for reasonable prices $20-$50 I think, but I've lost his address. i will have another look for it and post it if I find it.

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