From: Bill Collins (photo@intrex.net)
Date: 06/03/01-06:20:48 PM Z
Maybe this was already mentioned and I missed it, but an IR pinhole image would have inherently less resolution than a pinhole image at a shorter wavelength, wouldn't it?
Bill
---------- Original Message ----------------------------------
From: Marco Pauck <marco@pauck.de>
Reply-to: alt-photo-process-l@sask.usask.ca
Date: Sun, 03 Jun 2001 23:32:54 +0200
>heather hyatt wrote:
>>
>> marc,
>> > thanks for the help. my normal exposure is about 8
>> secs. i took the filter into account. it isn't a
>> problem with the exposure but more with a bit of blur.
>> i think perhaps that since pinholes are kind of fuzzy
>> and IR is sort of fuzzy too that might be the
>> problem.
>> i have stock piled Kodak HSI, it is too bad they
>> stopped making it.
>
>This is getting a little off-topic (well, not quite uncommon
>for this list ;-) but let me clarify this:
>
>I was not arguing about the exposure time but the diameter of
>the pinhole. The optimal diameter is a function of the distance
>to the film plane (the 'focal length') and the light's wavelength.
>Therefore, a hole that works perfectly for visible light will be
>sub-optimal for IR and vice versa resulting is more than usual blur.
>
>I'm not sure what you mean with "fuzzy", but IR is not more or less
>fuzzy than other wavelengths.
>
> Marco
>
>> > Note that IR has a longer wavelength than visible
>> > light
>> > (depending on the filter you've used, maybe nearly
>> > two times).
>> >
>> > You have to take this into account when computing
>> > the
>> > appropriate diameter of your pinhole.
>> >
>> > BTW: Kodak HSI went out of production recently ...
>> > :-(
>> > The only other 4x5 IR film available now is Maco
>> > IR820c.
>> >
>> > Marco
>
>--
>Marco Pauck -- marco@pauck.de -- http://www.pauck.de/marco/
>For every complex problem, there is a solution that is simple,
>neat, and wrong. -- H. L. Mencken
>
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