Archived posting to the Leica Users Group, 2009/11/17

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Subject: [Leica] Forscher's lights
From: h_arche at (H. Ball Arche)
Date: Tue, 17 Nov 2009 06:46:45 -0800 (PST)
References: <>

Back in the lith film/process camera days this was standard procedure in 
shooting halftones; there was a bump, which was a brief exposure of the film 
with out the overlaying dot screen, and the flash, which usually came after 
the main exposure, and was exposed through the dot screen. The idea was to 
punch up contrast.

The flash lamp hung above the back of the camera, hooked to a timer, and the 
exposure took place with the camera back dropped and the film held in place 
on the vacuum back.

----- Original Message ----
From: Lawrence Zeitlin <lrzeitlin at>
To: Leica LUG <lug at>
Sent: Mon, November 16, 2009 5:24:34 PM
Subject: [Leica] Forscher's lights

Slobodan writes:
"Didn't Forscher modify a Nikon with lights, in order irradiate the

elmusion for low light shooting?"


I don't know if Forscher was the first to do this but pre-exposure and
latensification used to be old tricks of available light photographers and
cinematographers to eke out the last residue of sensitivity of films.
Pre-exposure involved exposing the film to low light levels either prior or
after exposure. The idea was to get the image exposure over the toe of the
sensitivity curve. It effectively provided an increase in apparent
sensitivity of 1/2 to a full stop. Latensification involved exposing the
film to mercury or ammonia vapors prior to exposure. It could also gain a
one stop increase in sensitivity. These techniques are rarely used today in
this era of ultra high speed films. You can find more about them by looking
through old photo books and magazines. The use of lights in cameras was
described in 1950s era magazines such as "35 MM Photography".

One construction article suggested gluing 4 grain of wheat incandescent
bulbs on the inside of a Leica M camera near the corners of the frame. The
lights would be illuminated briefly by a battery switched on by the flash
contacts. The article suggested that this would work well with B&W film but
might give problems with color film because the lights would upset the color
balance of daylight emulsions.

I never tried gluing bulbs to the inside of my camera but I did experiment
with pre-exposure and latensification. Both worked but there was too much
variability in the process and it proved to be far more trouble than it was

Larry Z

Leica Users Group.
See for more information


Replies: Reply from mark at (Mark Rabiner) ([Leica] Forscher's lights)
Reply from s.dimitrov at (slobodan Dimitrov) ([Leica] Forscher's lights)
In reply to: Message from lrzeitlin at (Lawrence Zeitlin) ([Leica] Forscher's lights)