Pinhole photography help required-Urgent

r_cayne@PAVO.Concordia.CA
Wed, 05 Apr 1995 22:53:11 -0400

Am trying to build a pinhole in a can 3.5" in diameter and
height of can approx. 8" high. Used .001 inch brass shimstock and
number 12(.013") sewing needle to create hole in brass shim stock.
Calculated fstop to be in the 220 range. Shot 1 shot of a library
with reading on 1/30sec at f90 for 400ASA HP5 Plus film for shadow
reading and calculated exposure for the pinhole to be approx. 25 min.
including reciprocity factors.

Film was adequately exposed with shadow detail however details were
not as sharp as they should have been and fiber like starnds were seen
on the negative. I assume that the fiber like stands were due to inadequate
preparation of the hole, but I did take care. Please comment on the
following:

1)_ Is the brass shim stock selected too thin?
2) The fiber like stands -- caused by what?
3) How do you really tell if you have a clean hole?
By the way my hole was done under a bi-microscope at
90x.

4) Whn I attempted to make another hole I noticed when holding
the lens up to a regular light that I though I saw fibers
or a fuzziness through the lens although under 90x it seemed
clear. What the hang is going on? How to make the right
hole? Needle used by the way was a No!2 sewing (hand) and
was perfectly round.


Please send help, I really need it and if there are any FAQ's around on this
subject please advise as well

Regards,

Richard