Re: Larger negatives

Greg Schmitz (gws1@columbia.edu)
Tue, 16 May 1995 16:25:49 -0400 (EDT)

> From jseigel@panix.com Tue May 16 06:00:11 1995
> Sender: alt-photo-process@vast.unsw.edu.au
> Subject: Re: Larger negatives
>
> On Sun, 14 May 1995, Tomi Knuutila wrote [about contacting a print to
> make a negative]:
>
> > Isn't it true, however, that on fiber papers part of the emulsion lies
> > inside the paper, and that might blur the image, no matter how flat the
> > print is?
>
> I've been waiting for someone with some actual facts to answer this one
> (Greg? Are you there?).

Did I hear mention of my name?

Yes, I suspect you might loose some sharpness, though I'm not sure
how much (Louis? Are you there?). The loss of sharpness would
probably depend on three (well, maybe four) things: 1) the distance
from the negative to the exposed particles in the paper. 2) the size
of the light source used to make the exposure. 3) the distance
between the light source and the negative. 4) The percentage of
visible density contributed by "deep particles" exposed in the paper.
If the highest possible resolution is required, a point light source
would be in order.

You might, if you are interested in pursuing the subject further,
read about penumbra and umbra, the partly shaded region around the
shadow of an opaque body and the "full" shadow itself. Any good
intro physics or astronomy text should explain the topic in detail.
Anyway, IMHO shadows are well worth knowing about if you want to make
photographs - hardly an obscure topic.

--greg schmitz

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