Compensating Development Timer Redux

T

thronobulax

Very Active Poster
Registered User
Joined
Aug 29, 2020
Messages
1,339
Some years ago, I designed a development timer in the spirit of the Zone VI device of yesteryear. I believe I may have mentioned it here at one point or another.

In any case, the original design was just a prototype. I finally got around to actual "manufacturing" it into a case for day-to-day use. The site with all the technical details and photos of the completed instrument may be found here:

https://gitbucket.tundraware.com/tundra/devtimer

If you are handy with electronics, feel free to build your own. I am happy to answer questions as I am able.
 
A worthwhile and fulfilling project for sure! But, for those who may not wish to go down the DIY route and already have a laptop you may want to take a gander at this: http://curtpalm.com/Software.html

I have a Zone VI Compensating Timer hanging on my darkroom wall that I still use to this day for prints, but years ago I went with the CompnTemp Timer because it allows you to set a target temp (other than 20C) among many other adjustments. I run it on an old XP palmtop with a USB probe and USB footswitch and AFAIK it does what it's supposed to do.

Just thought I'd mention an alternative...
 
Good to see others thinking about the same problem! If you are the author of the program (or know them), I'd be curious how they arrived at their correction curves.

I did a fair bit of research, both forumula- and lookup based, to arrive at mine. It's an interesting problem.

Even more interesting is what do with film developers with high oxidation rates like PMK Pyro. I open tank process pretty much everything and open Pyro oxidizes fairly rapidly.
 
Last edited:
I am not the author or know the author...I'm simply a satisfied user of the software.

I haven't used PMK is many years, but I use a lot of Pyrocat-HD for several reasons; one of which is that it doesn't oxidize nearly as fast as pyrogallol-based formulas. That said, the only open tank development that I do is using tanks & hangers with Pyrocat-HD when employing minimal agitation techniques.
 
Is Pyrocat-HD available in liquid form like PMK or is it pretty much a DIY/Powder thing?
 
I mix it myself, but it's available in liquid form from Photographers' Formulary, if you're in the USA; I think Freestyle Photo carries it, too, but I'd recommend ordering direct from the Formulary. If you're in the EU, I believe Ian Grant (a member of these boards) sells it. There may be other vendors, too.
 
I did a bit of poking to find literature on the differences between PMK and Pyrocat-HD without much luck so far. If you have any such references, it would be very much appreciated...
 
There are a couple of sellers of Pyrocat HD liquid on the auction site.

There were problems with the Formulary kits for a while, so be careful.

Mike
 
The only reference I have is my own personal experience. IMO, these two developers are only similar in that they both produce a stained negative. PMK is a pyrogallol based formula, while Pyrocat-HD is a catechol based formula. PMK will produce a yellow-green negative while Pyrocat-HD will produce a yellow-brown negative. In my experience, a PMK negative will print very nicely on graded papers, but produces pretty flat results on VC papers. The Pyrocat-HD negative will print beautifully on both types of papers. Also, if you mix yourself, catechol is a bit less toxic; regardless, I wear an apron, nitrile gloves, face mask, and when mixing in the catechol I do it outside. If you look up Sandy King's writings, I'm pretty sure he covers the differences well.
 
You must log in or register to reply here.
Back
Top