re: Experiments with pinhole diameter

John Brownlow asks about pinhole diameter.

I did some experiments with a set of pinholes I have. It seemed to me
that the optimal
pinhole as determined by the formula did produce sharper results than
smaller or larger pinholes.

The formula that I use does not refer to the outer diffraction ring but
rather the size of the
central diffraction disk. The formula assumes that the optimal pinhole
is the same size as
the diffraction disk it produces. But remember that this is dependent
on wavelength so you
may get different results using panchromatic film than with
orthochromatic or blue sensitive
film or paper negatives. Anybody who has a set of laser drilled
pinholes can do this experiment,
just make a camera optimized for one of the middle sizes and take
pictures with different pinholes.
You can photograph a lens testing pattern and actually measure the
difference.

Another interesting experiment would be to make the same size pinhole in
stock of different
thickness and see how this affects image quality and covering power.
Received on Sun Nov 17 10:11:44 2002