Archived posting to the Leica Users Group, 1998/11/13

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Subject: Re: [Leica] Early Summitar
From: "Dan Post" <dwpost@email.msn.com>
Date: Fri, 13 Nov 1998 22:41:36 -0500

Walter-
Your story brought back memories- the idea of flashing film . The theory
behind that is that film has a threshold at the toe- no density at all until
that point is reached- I believe it is called the 'Speed Point' because the
amount of light to attain that point on the 'toe of the DlogE curve
determined the film speed. If you gave the film just enough exposure to get
it to reach that 'speed point' then any additional exposure would help bring
up the shadow detail! Tricky business- we used a dark green safelight at
about 4 feet for a few seconds- then re-spooled it!
 We used to 'flash our Tri-X when I was in high school so we could
photograph the night football games with the flashes we had available in
1965! We also tried fuming the film in ammonia fumes to make it more
sensitive, but that didn't work out too well.
It's refreshing to know we weren't totally out in left field then!
Dan
dwpost@msn.com