Compensating Developing Timer Accuracy?

[Doremus Scudder]

A recent thread about temperature control contained a comment about the possible inaccuracy of the compensating developing timer with different developers. The gist was: the Zone VI Compensating Developing Timer was calibrated for "standard" metol/hydroquinone developers. Other developer formulations may not exhibit the same curve of activity change in relation to temperature. Therefore the CDT might not be useful for these other developers.

I have used my CDT in my US darkroom for years with good results, but use good old temperature control when developing film in Europe, where I live half the year. Lately, a summer batch of PMK negatives, developed in the US with the CDT, came out a bit thin. Still printable, but not close to my usual accuracy in exposing and developing. The above comment got me thinking that possibly the CDT was not compensating well for the changed activity of the metol/pyro developer, (which would be less active at a higher temp than a M/Q developer based on my thin negatives...).

When I get back to the states, I'll do some tests, but that is not till December. I am interested if anyone else using the CDT has had experiences similar to mine, or has done any testing with different developers.

Best,

Doremus Scudder

[John Bowen]

I've used my CDT with HC-110 and Pyrocat-HD film developers and Dektol, Zone VI, Neutol WA and Michael Smith's Amidol paper developers. I have always received consistent results with these developers. I guess as so many on these forums state YMMV.

I'd be most interested in the results of your findings.

[Bruce Barlow]

I'll be specific: Fred Picker calibrated the CDT for HC-110B with Tri-X, and for Dektol with Brilliant paper. I believe he told me it took about a month, and was incredibly difficult. He had to cool or heat trays of developer 1 degree at a time, and keep it there for the entire film developing time of 5 to 6 minutes. He found that the time/temperature curves he developed did not match Kodak's. Were he to have done other combinations, he'd probably still be at it.

Paul Horowitz, a physicist from Harvard, invented the deveice, but needed Fred's work to calibrate it properly. Paul also invented the Cold Light Stabilizer and the spot meter modifications.

I don't know how much other time/temperature curves vary from what Fred did. All I know is that my experience matches John Bowen's, across other films, papers, and developers. It may not be perfect, but it's FAR better than nothing. You'd have to pry my CDT from my cold, dead hands.

[Kevin Crisp]

I've been using mine since they first came out. I do use it mostly with Tri-X and HC 110, but also Tri-x with Xtol and D76 1:1 and rodinal 1:50. I have used it with TMAX 100 and Xtol and D76, and both Arista Films in a number of combinations. I have never had a surprise. I don't use a thermometer, I just make sure the tap water is coming out under 80 (I have a dial thermometer on the water supply) and go with my original "time" established at 68 degrees by testing. I did not use it the few times I used PMK. Since I could measure the temperature and the tray temp won't change much in 6 to 14 minutes of development, I agree the convenience is relatively minor with film. I always measure and chart with roll film, not really that much trouble I have to admit. With paper, in hot Southern California darkrooms, it really shines. My developer can start at 80 and cool to 72 in an air conditioned darkroom during a printing session. Interestingly, set to "real time" it isn't the most accurate timer in the world and will drift a bit.

[jstraw]

Interestingly, set to "real time" it isn't the most accurate timer in the world and will drift a bit.

Since Paul Horowitz is an physicist, perhaps he encorporated some unpublished theories about the elasticity of time when programming the device's algorythms. Perhaps this *is* in fact, the most accurate timer.

[Alan Rabe]

I am a bit suprised that Fred Picker used Dektol for a developer, he hated it. That's why Zone VI came out with it's own print developer which I still use. I also know that in another thread Richard Ritter debukes the statement that tri-x was the only film used for the ZONE VI modified light meter. He states Fred told them to do it that way but they knew better and did an average of many films. But told Fred they did only Tri-X. I suspect the same is true on the timer. I have one and have used it for 26 years with out a glitch and as another has said "only from my cold dead hands' will I part with it. I also use the ticktok for exposure and feel the same way. They make life so much simpler.

[Bruce Barlow]

I am a bit suprised that Fred Picker used Dektol for a developer, he hated it. That's why Zone VI came out with it's own print developer which I still use. I also know that in another thread Richard Ritter debukes the statement that tri-x was the only film used for the ZONE VI modified light meter. He states Fred told them to do it that way but they knew better and did an average of many films. But told Fred they did only Tri-X. I suspect the same is true on the timer. I have one and have used it for 26 years with out a glitch and as another has said "only from my cold dead hands' will I part with it. I also use the ticktok for exposure and feel the same way. They make life so much simpler.

I hate to burst your bubble, but by hating Dektol Fred could sell more Zone VI developer.

"What is Zone VI developer?" I asked Fred when I worked at Zone VI. "Dektol," Fred told me (and I quote), "Why screw around? It's the best. ..." Fred knew that almost no one would test Zone VI vs. Dektol head-to-head, and so the secret was safe.

Sorry. And Fred did the time/temp testing himself, so there was no way he was going to "average." And yes, he used Zone VI print developer. My slip in the original post, based on the above.

[Alan Rabe]

Thanks Bruce, I didn't know that. I didn't know Fred could be so devious. Anyway I have been looking for a different developer because I don't trust Calumet to continue selling it. Now I know I don't have to look far.