Re: Pinhole Enlarger Questions

----- Original Message -----
From: "CJ Rumpolo" <rumpyhw@yahoo.com>
To: <pinhole-discussion@spitbite.org>
Sent: Saturday, August 21, 2004 10:47 AM
Subject: Re: [pinhole-discussion] Pinhole Enlarger Questions

> Thanks a lot for the information. I was using the lens maker equation and
I
> kept getting 100 as a focal length and well that was what made me decide
to
> post this message. So if I were to use an "ideal" pinhole then I could
make
> the lens to paper distance 100mm.

No.

If you use an "ideal" pinhole caculated for 100mm, the distance lens to
paper has to be 300mm, as illogic as it may seem to you.

If the distance pinhole-paper were to be 100mm, the negative will have to be
50mm from the pinhole and the focal length of the "ideal" pinhole you have
to use in this set up is 33.3mm. I don't think you want to enlarge a 4x5
negative with a lens that short.

The above will get clearer if you study the lens equation stated in my
previous message and that will also help you understand the bellows factor.
Ask me if you have question on this.

> I would like to thank you.

My pleasure.

> This enlarger will be hopefully added to the
> unit to get the students more involved with the physics behind the art.

Not a bad idea! Understanding the basics of math and physics of photography
is a good thing, contrary to what some people believe, makes doing things
easier, it may even liberate us so we concentrate in what we really are
trying to do/make. Besides, is not as if we have to be the proverbial
"rocket scientist", elementary high school algebra, trigonometry and
geometry is more than enough.

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Received on Sat Aug 21 17:06:41 2004