Pinhole Enlarger Questions

Hi, I have been mentally playing around with an idea to make a pinhole
Enlarger. Up until now I have been contact printing my 4x5 negatives but
would like to make a few into 8x10s. I have been looking for information
regarding this idea but so far have only seen site that describe replacing
the enlarging lens with a pinhole. My idea is to make an enlarger that would
project a 4x5 negative onto a sheet of 8x10 paper and enlarge the 2x. I have
made up a basic design and it looks like it may work but I feel like I am
missing some tidbit of information. What follows is what I have done. And
any suggestions would be most appreciated.

I decided that on a 4x5 enlarger a 150mm lens is the normal lens. So I made
up a foam core box that has two sections. The top section is 150mm in height
the second section is 300mm in height. The partition between the two
sections is where I placed the pinhole of about 3/32'' (it may no be optimal
but I was hoping to see an image). To the partition that is 150mm in length
I made up a negative holder to place a 4x5 negative. On top of this negative
I placed a battery powered light box. When I darkened my work area and
turned on the light box I did see an image being projected onto the base of
the 300mm section. It was very dim so I could not tell for certain that my
negative was being projected. I could not test out my idea using paper only
because I currently have no way to develop 8x10 paper and I could not made
the enlarger completely light proof (lack of foam core). SO I just purchased
an 8x10 film holder and will now construct a new design of this enlarger to
fit the film holder. Basically, I think what I am doing is making 2 cameras
in one (a 150mm 4x5 camera and a 300mm 8x10 camera) which are sharing one
pinhole. I hope that makes my description more visual. Anyhow now for my
questions:

Is there a minimum focusing distance in pinhole cameras?
Do I make a pinhole to match the 150mm focal length or the 300mm focal
length?
Is the f-stop very critical for this application. Since I am only concerned
with a narrow plane of focus can I open the f-stop to allow me to better see
the image being projected and also to speed up exposure time?
Does this idea seem plausible?
Are my distances accurate for the size of enlargement?
Am I missing anything before I make up my new prototype?

Again thank you for your time and for any comments. If I make any progress I
will happily the group know.
            Chris

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Received on Fri Aug 20 07:56:00 2004