Are you trying to make a pinhole Camera? If so you dont place the pinhole
in front of the lens you REPLACE the lens completely - so it should be
mounted in a (Black) body cap not a lens cap.
I may have got hold of the wrong end of the stick here so if so ignore what
follows.
The small hole will give a very wide angle and large DOF so focusing is not
an issue. It is unlikely that there will be sufficient light transmission
for your camera's meter to register so long exposure and experimentation are
the trick here. Also the precision of the pinhole will greatly affect the
sharpness of the image.
I made a pinhole camera many years ago with just a biscuit tin - school
project. A great way for kids to learn the basics of photography. Just put
a tiny hole in the lid - it needs to be small and precise so just banging a
nail in is not good enough. The inside of the tin needs covering with black
paper (or paint) to stop internal reflections. I used mono photographic
printing paper instead of film cut to the size of the tin and mounted (in
darkness) face up on the bottom of the tin. Put the lid on and close the
shutter by sticking a piece of black electrical tape over the hole. Remove
the tape to expose the paper replacing it again after timing the exposure.
Develop the paper as normal and use the paper neg to make a contact positive
print.
Exposure can be found by experimentation but tests of around 1 min should
give a result.
Again I may have misunderstood the objective but ne're mind eh?
Peter
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of Dan Scott
> Sent: 04 March 2001 06:31
> To: [EMAIL PROTECTED]
> Subject: glenn's peephole fisheye
>
>
>
> >In completely unrelated news, I finally got around to making a hole
> >in a lens cap to mount one of those fisheye peephole thingies I got
> >at a hardware store many months ago, and played with it on the front
> >of an M42 50mm briefly. It does want a short extension tube behind
> >it (and if there's a 2x converter behind _that_, the image becomes
> >a reasonable size in the viewfinder), but I noticed that I was unable
> >to focus (with or without the 2x). There was a definite point of
> >_least_ blurriness, but at no point in my experiments was anything I
> >saw through it _sharp_. Holding it up to my eye, things look sharp
> >through it. I don't really understand why (though if anyone does
> >understand and wants to have a crack at explaining it, I'd be grateful).
> >I'm guessing that it doesn't project an image the same way a normal
> >photographic lens does, but relies on the eye to focus _through_ it.
> >But I don't understand why the camera lens can't focus through it.
> >
> >
> > -- Glenn
> >
>
> Might be that the minimum focus distance of your eye is better
> than that of
> your M42 50mm. Sounds like a cool project, though.
>
> Dan Scott
> [EMAIL PROTECTED]
>
>
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