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Enlarging Computer? What is this?

Dave Nicholson , Apr 06, 2001; 09:18 a.m.

Some time ago, when I bought my enlarger second hand, it came with a piece of equipment called a 'Paterson CdS enlarging computer' It has two dials. One for exposure time and another for paper speed, ranging from A-M.

So my question is, what is this thing for? does it calculate the exposure time needed for a print?

Thanks for your help


Joe Lipka , Apr 06, 2001; 10:36 a.m.

I am not familiar with this specific piece of equipment, but have used others similar to it. It acts as an exposure meter for your enlarger. For a specific negative and paper combination, you can calibrate both the highlights and shadows of a test negative on your enlarger easel. Then load any other negative (of the same film type)into your enlarger, and read the highlights and shadows of that negative on the easel. You then adjust the enlarger aperture to make the meter read the same as your test negative.

This system works well if you keep using the same film, paper, enlarging times, developer and developing time. The only variable is the enlarger lens aperture.

Boris Krivoruk , Apr 06, 2001; 12:02 p.m.

Dave, what you refer to is not really a computer. Kodak makes similar enlarging calculators. This is what it does: you have to print at least one good picture with the exposure that you like. After that if you decide to change the size of the photo, moving enlarger's head up or down, then using that calculator it can give you correct exposure for new enlargement. But first you have to know good time and f stop for at least one enlargement which you set as a base on the calculator.

Keith Nichols , Apr 06, 2001; 06:04 p.m.

You might contact Saunders, who handle Paterson in the U.S. As for me, I'm not sure whether your gadget is just a type of circular sliderule or an electronic device with a photosensitive cell. The inclusion of "CdS" in your title for it suggests the latter. The Paterson section of the Saunders web site shows such a thing. I had one for a while. As I recall, you make a good print, and without changing any enlarger settings or removing the negative, and keeping the exposure time in mind, put this gadget on the easel in a spot of your choice, turn on the enlarger, and instruct the gadget to light a green light whenever it sees light of that intensity. With subsequent negatives, you adjust the f stop until the green light goes on, and expose for whatever time worked the first time. It's suggested that you pick a medium grey spot to meter each time. I only kept the gadget for a day or so and am not clear on the detailed mechanics of calibrating, but that's the way it was to work out.

A Talug , Apr 06, 2001; 06:28 p.m.

Dave: What you have is an incident light meter with a CdS (Cadmium Sulfide) light sensitive cell. It will help you reproduce a given negative density-to-print density relationship from one print to another.

Miguel Azar , Apr 07, 2001; 12:36 a.m.

Analite II Help

Hi: I tried posting earlier on my Analite II, but received no responses. So I will try again. Does anyone know how this "enlarging computer" works. I bought it about 20-25 years ago when I was rather young. I have no manual and would like any help on how to calibrate and use it. For the sake of the trees and my photo budget - someone help. Thanks in advance.

Keith Nichols , Apr 07, 2001; 12:17 p.m.

Miguel, craigcamera.com lists manuals for Analite 300 and 400 models for $12. They are listed under instructions manuals as Beseler Analite meters. You might also contact Beseler directly.

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