Pinhole Focus

Hi !
I'm Ian McKee and I've been following the discussion on focus of pinhole
images and I think some of you are getting more complicated than necessary.
Calumet sells a set of twelve pinholes ranging from .0059" to .032". I have
mounted these on a 4" x 5" camera and shot the whole series at an
arbitrarily selected bellows extension=focal length of 210 mm. With each
pinhole I get the same image and the same degree of sharpness. The only
variable is exposure time.As you might expect, the smaller the pinhole the
longer the exposure to achieve equal density.
That tells me that the selection of a focal length for a given pinhole is
based on optimum exposure time. If I were to make exposure time constant,
say, 10 seconds, then, for each pinhole I would find an optimum focal
length to give me equivalent density.
Conversely, If I take one given pinhole and vary the bellows extension or
focal length, adjusting the exposure to compensate, I can get any image I
want, from wide angle to narrow angle (telephoto).
Try it and see for yourself!
 
 

--- Ian McKee
--- photoian@earthlink.net
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Received on Sat Dec 14 12:29:11 2002