Re: wondering

erickson@hickorytech.net writes:

> It occurs to me that lack of sharpness in pinhole images is not
inherent to
> the nature of diffraction photography. It is caused by lack of
precision in
> matching the diameter of the pinhole to the distance to the film, or
in less
> than perfect pinholes. Thus it could be said to be a lovable blemish
> attributable to the operator rather than an essential characteristic
of the
> process to be defended against heresy. Or something like that.

Lack of sharpness is directly caused by diffraction. The optimal
pinhole
for 100mm focal length can only resolve about 5 lines/mm. In addition,
there
are a number of things that can degrade performance even farther.
Pinholes
are computed for a specific wavelength, but when we use normal
panchromatic
film, the image is formed by a range of wavelengths. Most of the tables
are
computed for green light, but we are using everything from blue to red.
And if
you look in Eric Renners book, you see that there are various tables for
pinhole
size that are different because they are based on different theories.
The point is
that pinhole size is not that critical and we mostly don't use them in a
way to
create maximum sharpness.
Received on Wed Dec 11 08:39:08 2002