Compensating Developing Timer

I have seen that quite a number of people here like to use the Zone VI timer. These units are getting quite old now and I think parts are difficult to obtain. I have also heard that these timers can drift out of calibration with time, although I’ve not been able to confirm this.

We have therefore started production of a new timer offering similar functionality to the Zone VI. It is not clear to us what demand there will be for such a device in these increasingly digital times so developing this device is therefore somewhat speculative on our part. However we felt it would be useful to some and have therefore produced a small batch to gauge demand, with larger volumes to be produced depending on how well it sells.

I’d be interested to have any thoughts on it (and some sales wouldn’t go amiss either!)

Here it is:

http://www.dlgelectronics.com/compensatingtimer.html

Thanks,
Dave

Well, I'm really glad someone is making these (again) and would be interested in the future after one my two Zone VI compensating timers bites the dust.
However there are a few questions and suggestions that immediately come to mind after viewing the webpage.

First, the Zone VI timer had separate settings for film and paper. Ostensibly, this was because paper and film required different compensation curves. I'm not really sure what was done or if it was even necessary. However, I'd appreciate it if you'd address this.

You don't show your footswitch on your website. A picture would be nice there. Or, is the "Remote Switch" the footswitch? If so, it seems a poor design for floor use, since the user would have to mount it on a board or the like. A real heavy-duty easy-to-step-on footswitch would be nice.

And, the two meters of cable you supply with the footswitch won't be long enough for many users (certainly not me!). The Zone VI timer had a real advantage in using standard telephone connecting cables, since it was easy to extend or split them. My current Zone VI timer has two foot switches connected to it by means of a phone-cable splitter and extension cables so I can have switches at opposite ends of my long sink. If you use standard audio jacks or the like, then the user could certainly put together a custom installation if desired or place the footswitch farther than two meters away from the timer by using a standard extension cable. However, it's not clear if this is possible.

Also, knowing what the connectors and the cables looked like would be good. There are not even illustrations of them in the instruction manual. Even the temperature sensor you picture seems different from the one illustrated in the tray-clamp instructions. Generally, you could really use better illustrations of your products and how they are used in practice.

Along the same lines: It's really hard to know the scale of the things you do picture. How big is that sensor anyway, and how does it sit in a tray of developer without the tray clamp? My current sensor goes into the water bath tray when I'm tray developing sheet film, but directly into the developing tray when processing prints.

Your timer beeps at intervals of one minute. Most of us agitate at 30-second intervals. It should be pretty easy for you to change that; beeping twice a minute is not a problem for those agitating at one-minute intervals and would make your device much more user friendly for those that agitate at 30-second intervals.

Volume control for the beep would be nice too. Some of us don't hear well and some (me, for instance) are annoyed by loud beeps in the darkroom.

How waterproof is the unit? Can I operate the switches with wet hands and not risk damaging it?

Your largest market is going to be in the U.S. You need to provide prices in U.S. dollars and transparent shipping costs and times on your website if you want to make transactions user-friendly for foreign buyers. Other currencies (e.g., euros, despite the Brexit ) would be nice too.

It's really nice to see all the temperature-conversion curves based on different coefficients. However, this begs the question: which photographic materials need which coefficients? Have you tested different films and papers? Or, are you simply relying on Ilford's research and published data for your default setting? How am I supposed to know if I need a different coefficient built in than the one you provide as default? Do you expect your buyers to do tests on their favorite materials themselves, or are there sources where one can get such information? What good is having so many choices if one doesn't know which coefficient their particular film or paper requires?

The communities here and over on the LF forum are really knowledgeable, so I expect you'll get a lot of interesting and helpful feedback in addition to mine. I look forward to maybe adding your device to my darkroom someday.

Best,

Doremus

Doremus,

Thanks for the comprehensive response, which will take me some time to digest and address in full.

As an initial response on a few of the items:

I can find no evidence that film and paper require different compensation curves, as far as we have been able to establish the curve is dependent on the developer type. It is not clear on what basis seperate curves are provided on the Zone VI. Anecdotaly, I have heard it said that the two setting on the Zone VI are very similar - however to confirm this I would need to acquire a Zone VI timer in factory condition (to be sure that nobody has tampered with the factory calibration), and plot out the curves (straightforward to do).

The remote switch and foot switch are the same thing - I’ll tidy up the terminology on the website for clarity. I may see if I can source an additional switch designed specifically as a foot switch to offer as an option. Any momentary-action switch with normally-open contacts could be used and there’s no reason why any such switch could not be connected to a 3.5mm jack and plugged in.

The connectors are both 3.5 mm jack. I’ll include pictures showing cable and connectors. I’ll also make it clear that a suitable jack extension (3.5mm male to female) could be used if required.

The sensor is approx 6 inches / 150mm long and 1/4 inch / 6mm diameter. It is, I think, the same one in the two pictures; certainly it is the same model. Again, I’ll provide better illustration on the website.

I’ll change the beep interval to 30s. This is simply a software change and I can reprogramme our current stock accordingly without difficulty. A question here - do you agitate at 30s intervals in real time, or in compensated time? Presently we beep at 60s compensated, which would mean a shorter interval at higher temperature (or longer at lower temperature).

A volume control could be provided if useful. In the near term we could modify the design slightly to do this but it this but it would require the case to be opened (4 machine screws to undo on the rear) and a screwdriver adjustment made. Longer term we may be able to provide a front panel control. Note that the beep is only operative when the display mode is “off”, although a simple software change could be made to render it operative regardless of the display mode.

The unit is not waterproof. If you drop it in the developer tray there would be some ingress of fluid. If this happens there should be minimal damage though - if this happened we’d recommend opening the case, removing the batteries, rinsing out with clean water and allowing it to dry before closing and re-using.

The switches, whilst not waterproof, will be fine to use with wet hands - they are designed such that a few drops of liquid would not reach the switch mechanism or contacts, which are shielded internally. We did consider using a membrane switch to improve waterproofness but decided against that as they would not allow for easy feel/touch sensing when using it in total darkness.

I’ll see what I can do with other currencies. I’m trying to sort out US distribution for the future (as for our exposure meter which is available through CatLABS in the US).

I would expect the majority of users would be happy with the implemented default curves. These correspond to the widely-used Ilford time-temperature charts. Is there anybody using anything different to these? We’d only recommend a different curve if someone where using a specific developer of known and very different characteristic - softer developers seem to have lower temperature coefficient eg a pure metol-based developer might need something more in the region of 1.5. However, I’d note that most developers are a mixture of active ingredients, all operating with different temperature coefficients, and that therefore any single compensation curve will be a compromise. It is for this reason that you should really get the temperature as close as possible to the ideal value and only use correction (either using standard charts or a compensating timer) to address the residual temperature error.

We haven’t run tests across a wide range of developer/emulsion combinations - the extent of testing becomes prohibitive if one attempts to cover every film and every paper in combination with every developer. Nevertheless if there are certain combinations which are popular we can run quantitative tests on these and provide some guidance accordingly.

Thanks again

Dave

I too am delighted to see a potential replacement for the Zone VI timer; so far, mine is still working fine after almost 30 years and is indispensable in my darkroom. The only comment I would make is that, according to Fred Picker in the Zone VI Newsletter, when they developed the timer they actually tested both film and paper to develop the time/temperature curves and discovered that, while film and paper differed, there was no difference within each category—that is, the film curve was the same regardless of film or developer type. The same with paper. I’ve never tested this, but the timer works as advertised for both media.
Good luck with this. And do share this info on the large, extra large and medium format sections.

Cheers for your project, I wish you success.

I agitate on 30 seconds as well. Though I run a Gra-Lab at the same time and might be a little real time/little compensates time. I think that’s fine to be compensated.

I have the ability in your competing product (CompnTemp) to edit the coefficient. I never change it though. So from my perspective it’s a non issue. The reasoning is that Metal and Hydroquinone have different coefficients and the real compensation is always a compromise. Different developers have different proportions of these two chemicals, so the best compromise is different for film (D-76) and paper (Dektol). It’s a compromise anyway, so the original design (film/paper switch) was good. To reiterate, there’s a good reason for the choice, but it’s not critical.

Different developers need different compensation curves, some are less sensitive to temperature change than other. Metol based developers drop in activity very quickly as you go below 20ºC, yet Rodinal which is p-Aminophol based doesn't.

Somewhere I have a chart, I think in a book or data-sheet with a comparison, choice of film or paper will make a difference as well. I just had a look in the obvious books in my darkroom but no chart. I have a feeling it was a Kodak chart.

Perceptol will have a significantly lower Coefficient factor than ID-II/D76.

Ian

I too use the Zone VI timer. Alas I long ago gave up using the compensating part of the timer. I just use the normal setting and everything works fine. I always thought the whole idea was a little wonky but I do love the timer!! You must include a foot switch! It's a great thing you have done Dave!!
best, Peter

Dave Gooding said:

Doremus,

Thanks for the comprehensive response, which will take me some time to digest and address in full.
...
I’ll change the beep interval to 30s. This is simply a software change and I can reprogramme our current stock accordingly without difficulty. A question here - do you agitate at 30s intervals in real time, or in compensated time? Presently we beep at 60s compensated, which would mean a shorter interval at higher temperature (or longer at lower temperature).

A volume control could be provided if useful. In the near term we could modify the design slightly to do this but it this but it would require the case to be opened (4 machine screws to undo on the rear) and a screwdriver adjustment made. Longer term we may be able to provide a front panel control. Note that the beep is only operative when the display mode is “off”, although a simple software change could be made to render it operative regardless of the display mode.
...
I would expect the majority of users would be happy with the implemented default curves. These correspond to the widely-used Ilford time-temperature charts. Is there anybody using anything different to these? We’d only recommend a different curve if someone where using a specific developer of known and very different characteristic - softer developers seem to have lower temperature coefficient e.g. a pure Metol-based developer might need something more in the region of 1.5. However, I’d note that most developers are a mixture of active ingredients, all operating with different temperature coefficients, and that therefore any single compensation curve will be a compromise. It is for this reason that you should really get the temperature as close as possible to the ideal value and only use correction (either using standard charts or a compensating timer) to address the residual temperature error.

We haven’t run tests across a wide range of developer/emulsion combinations - the extent of testing becomes prohibitive if one attempts to cover every film and every paper in combination with every developer. Nevertheless if there are certain combinations which are popular we can run quantitative tests on these and provide some guidance accordingly.

Thanks again

Dave

Click to expand...

Dave,

Thanks for the comprehensive reply!

As for your question: Yes, I agitate once through the stack every 30 seconds, compensated time (which means I have to hurry in the summer, but can relax a bit in the winter).
Having the beep activated together with the display would be very helpful. I could then look away from the display and still have a signal to keep me agitating on schedule.

The coefficient you decide on for standard should probably reflect the most commonly-used developer(s). Looking into the curves for D-76, Xtol and a few others for film and for Dektol, Liquidol, etc. for prints might be illuminating. There are many here that use PMK or Pyrocat staining developers. Offering a separate coefficient for those, if they are significantly different, might be a good idea. You may want to communicate directly with Ian Grant, who seems to have data on temperature-change effects for different developers to maybe save some testing time.

Your timer seems more robust than the Zone VI model. I'm looking forward to seeing the improvements. FWIW, the Zone VI has holes in the front panel to access pot screws to adjust volume and brightness; it's not waterproof at all. However, once you set it for film or paper, you never have to touch it. The footswitch is all you need. That's why I think you should opt for a really robust footswitch or at least offer one as an option. For those of us who get our hands wet developing, a footswitch is indispensable.

Best,

Doremus

That's interesting and heartening to see something new in development.

Though I have to say, I'm spectacularly fond of my IOS developing app (Develop). It doesn't have the compensation function (which seems like it would be an easy update to the software), but what I like:

Sort of a clock-face type display alongside a numerical display. I can keep an eye on it and know when to be ready to agitate;

Set it to chime at intervals - I agitate every :60 and it gives a little chime, really handy. Has a darkroom mode that's dim and red, too. Nameable memory slots for different recipes, like "FP4, 1 stop push, Rodinal" kinds of things.

My problem is an ADD-ish, low level boredom threshold, so those 60 seconds intervals seem like weeks, and I do things like test fixer, mix HCA and so on, so the chime is handy for my colander-like brain.

Thanks all for the helpful comments.

The footswitch requirement seems the most pressing point here and is readily addressed. I will substitute this one for the remote switch currently offered if people feel it is suitable.
https://uk.rs-online.com/mobile/p/foot-switches/8086989/

We’ll update our website soon to reflect this but in the meantime any orders received together with a request for a footswitch substitution through the feedback form on the website (under “contact us”, http://www.dlgelectronics.com/feedback.html) then that is what will be supplied.

Of course I realise there’s nothing to stop anyone from just buying the RS one above directly, soldering a 3.5mm jack on it, and saving themselves a couple of pounds/dollars, thereby depriving us of our modest mark-up for fitting the jack plug!

Updated firmware with a 30 second beep interval will be released within a week, and existing unsold stock will be reprogrammed to the new standard.

Other suggestions such as multiple selectable temperature coefficients were considered in the design but rejected as adding complexity and moving away from the “extremely simple to use, especially in total darkness” philosophy of this unit. However, we are considering a much more feature-laden product in the future, which would offer multiple coefficients, user-programmable options, factorial development assistance and so on and so forth. Of course, this would involve a lot more button-pushing and knob twiddling, would therefore be harder to use in the dark, and cost more too! We’d need to sell something close to 100 units to break even on a unit of this complexity and not sure if there would be enough demand. We would see this as being a distinct, seperate, product rather than a replacement for the current one, as we feel that for many the simple to use timer that lends itself to error free usage in the darkroom would be preferred (no wondering after we’ve got halfway through developing our precious negatives if we’d set all the options up correctly or pressed the wrong buttons or something!). Nevertheless if comment here is supportive of such a product we can get a concept study done. We might consider introducing this as an app for smartphones with a plug-in sensor, since we have got someone looking into smartphone apps with sensor interfacing now anyway.

Dave

All,

Following the comments we have now included a foot switch instead of the remote switch previously provided, and changed the “beep” interval to 30 seconds.
http://www.dlgelectronics.com/compensatingtimer.html

Dave

Update - now available in the USA from CatLABS of JP:
http://www.catlabs.info/product/temperature-compensating-development-darkroom-timer