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Posted by Doug on December 26, 2001 at 22:46:30:
In Reply to: Weston Mitchell Fotoval Model 747 posted by Ron Knight on November 06, 2001 at 19:00:09:
: I stumbled on your web site trying to find information on a piece of equipment I acquired in a lot of darkroom equipment. It states; Weston Fotoval Model 747, distributed by Daystrom Limited in Cooksville, Ontario, Canada. I realize it is a densitometer of sorts because it has a light sensitive device that rests on your easel and reads the light intensity projected through a negative. It has a knob for setting your paper sensitivity and a brightness adjustment with a needle scale on the cabinet. I am hoping to find some detailed information on how it is used or even better, a manual. I have searched under Weston, Mitchell, densitometers & Daystrom, with no results. Can anyone direct me in the right direction?
: Ron
Although there is very little on the web about this piece of darkroom equipment, you are describing a darkroom exposure meter, a densitometer used to determine the exposure time for the enlarger. Although I am unfamiliar with the Weston Fotoval, these devices work in one of two ways. First the ANSI paper speed (usually found on a printed circular enclosed with the paper) is set on the paper sensitivity gauge. Then under darkroom conditions, with the safelight off and the negative projected on the baseboard, the probe is set on a portion of the projected negative which you want to be exposed as a detailed highlight. A dial is turned until an indicator light goes off, at which time the number of seconds exposure is indicated, usually by reading a scale on the dial. The other way these devices work is by maintaining a constant exposure time for all enlargements (i.e. 10 seconds) and by closing down the aperture on the enlarger lens until the indicator light on the densitometer goes out. Then you print the enlargement.
All darkroom exposure meters require some calibration, which can include adjusting the ANSI paper speed sensitivity up or down to reflect your working methods. Consistently successful results come from learning to read the projected negative and learning to place the probe in the same tonal portion of different negatives. Darkroom exposure meters can be calibrated to the person's own tastes. For example they can be calibrated to read mid-tones or shadow areas of the negative. In the darkroom today most enthusiasts use variable contrast paper, therefore it is important to remember that the choice of contrast filter may change the ANSI speed of the paper.
I found your darkroom exposure meter for sale at http://www.arvideo.freeq.com/catalog.html
The listing says "Mitchell Fotoval, Weston model 747 with probe- uses darkroom paper key insert $15" which suggests to be that your equipment may be missing the "darkroom paper key insert" - I don't know what that is.
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