That's basically it, but the other night we had a pinhole making session
and after making a hole myself in about, I'd guess, half an hour, I
watched two other persons work for a couple hours and not quite get the
right dimension and not quite get the inside clean. The message is that
my experience in making holes (I have made hundreds) is part of the
answer to your question. So don't get discouraged! Like anything else,
skills are acquired by practice.
Oh yes. It helps to darken the silver to diminish flare inside the hole
and from the surface of the silver. Selenium toner is what to use for
that. DON'T use PAINT! Toner leaves the hole clean and does not change
the dimension. Not so paint!
As far as the diameter to shoot for, that depends. The original formula
I used I got from the photo lab index. d for diameter, f for "focal
length" (since pinhole does not focus, this is a faux term):
d=the square root of .00007f (values in inches)
This gave me very good results, but I have since gone to much smaller
values than .00007, and don't know where I will stop. The experts say
that there is a point of diminishing returns, that diffraction will begin
to cancel improvements in resolution achieved by reducing the hole size.
I have yet to find this point, and have come to believe that the quality
of the hole itself is of paramount concern. At the present time, I think
I am approaching commercially acceptable standards for architectural
imaging. Of course, if we are making pinhole cameras for reasons of
simplicity (they have a terrific virtue in that dimension, to be sure),
this may not be a desirable quality.
I am currently working in the f/300 - f/400 range on 4x5 materials using
extremely wide field cameras.
Anyway, give it a try. IMHO there is nothing more fun than this. To
think I did photography for more than a decade before I got around to
building my first pinhole camera!
If you can find the _PJ_ article cited, it still has a lot of other
information you might find useful as well as some assignments I gave my
students to develop an understanding of perspective.
Enjoy.
Larry Bullis
Shoreline Community College