I use the StopClock Vario with a Beseler Dichro 45S head. I don't really use the "vario" cold light probe but I bought thinking that some day I might want to try a cold light.
The timer is one gadget I would not want to lose. It has completely changed the way I print and even the way I think about printing. Also, I make better prints because of it. Well worth the money. Definitely get the footswitch. If I did it again, I might buy 2 footswitches because they seem flimsy comapred to the timer which seems very well built.
I also recommend their flashing devise. Without it, I don't think I would have bothered to experiment with flashing but now I find it very useful at times.
I'm not very familiar with the Zone VI heads other than the VC version and the Compensating Timer. If you have a Stabiliser, I assume this is intended to fix the old cold light problem of varying intensity. A voltage stabiliser alone won't do this for cold light, but a purpose-built cold-light-stabliser will. If you have one of those then you don't need a compensating timer. In which case you can quite happily use an Analyser Pro without problems - or indeed a standard StopClock Professional and/or a ZoneMaster II.
To clarify - the Analyser Pro is not the same as a StopClock Pro + ZoneMaster combination; its timer is not so sophisticated. There is only one channel, no dry-down compensation (which you won't need anyway if the meter is properly calibrated to your equipment) and no programmable exposure sequences (although there is a neat burn-in feature).
A compensating timer such as the Zone VI one or our StopClock Vario measures the light output from the enlarger lamp and adjusts the exposure time to compensate for any changes. If the lamp gets brighter, the time gets shorter so that the print exposure remains constant, and vice versa. The issue here is with exposure metering; any exposure meter bases its calculations on the light level it sees when you make a measurement. If that light level subsequently changes (due to lamp output fluctuations) then the calculation will be wrong. A compensating timer can correct for this. However, if the light level changes during measurement (our meters typically require two or more measurements to establish exposure and contrast) then the compensating timer cannot correct the exposure.
In summary, we have many users of Analysers and ZoneMasters together with cold light enlargers who get good results. Providing the tubes are well warmed up prior to printing and left on as much as possible the light output variations are minimised.
For best results with cold light I recommend either a compensating timer such as our StopClock Vario, or a lamp stabiliser. You do not need both. The latter route allows more accurate exposure metering, but if you prefer to establish exposure and contrast by making test strips then either will work just as well.
Hope that helps!
Cold light heads present a bit of a problem when used with any timer be it an F-stop unit or a linear timer. As the tube warms up the amount and spectrum of the light changes and it also changes as the tube ages. Some cold light sources are very sensitive to dips in line voltage. Additionally there is a delay each time the lamp turns on and this delay time has some variation to it. As Richard mentioned, the most viable solution is to use a stabilized power supply or closed-loop intensity control and to keep the lamp warm.
A compensating timer, correctly called a ‘light integrator’, will help a lot but is not a panacea. Proper integrators for use with cold lights and HID lamps do exist and my firm has been developing them, along with stabilizing power supplies, since 1979. These systems have only been used for pre-press graphic arts, an industry that succumbed to computerization quite a while ago and is now quite moribund.
The contrast control on the older Zone VI heads - the one with the letters ‘A’ - ‘H’ on a pair of knobs - has a few holes in it’s range of contrast adjustment and most workers use these heads in split grade mode. The newer ZVI LED head does not have this problem. If you need to split-grade print with the older head then the RH timer may be more to your liking.
The Darkroom Automation timer and meter are designed for use with contrast filters, VC/color dichoric heads and LED heads. Although lacking the RH timer’s split-grade and compensating features the Darkroom Automation timer has easier to use dodging and burning controls and a more flexible test strip facility. The RH timer displays seconds that are adjusted up and down by variable stop increments. The DA timer is a pure stop-timer and displays and adjusts time in stops.
Only you can make the decision as to which equipment will meet your needs. That can be hard unless you can play with the equipment. F-Stop timers are a small market that can’ t support a large distributor and dealer network. Even if you can find a local photo-shop they won’t have any DA/RH/Nocon/Unique timers you can try out.
Darkroom Automation’s timers and meters come with a 30-day satisfaction guarantee. You can try one out and if it doesn’t meet your needs you are only out the return postage. I don’t know RH’s policy on this, but I see Lee has offered to show you his RH unit.
Most important, have fun.
Whew - a lot of info in this thread, most of it about the timer issue.
My twocents on the head and filters:
I use an old Zone VI timer with foot switch (old fashioned, I guess, but works for me) with an Aristo head. See here - http://www.aristogrid.com/prod02CC_CL45.htm . This head has a filter drawer for standard 6" Ilford filters (placing them in the light path, where they won't degrade the image sharpness). The bulb is the new V54 designed for use with VC papers. When I built the darkroom, I put the enlarger on its own circuit (even the bulb heater and timer are on a separate circuit). I have never had variation that I can see (I'm pretty discerning about this, and Allen Johnson, the old president of Aristo told me it would work).
The reason I did not buy the dual bulb head (http://www.aristogrid.com/prod02BA.htm) is that it doesn't have the brightness of the CL45 (confirmed by Aristo) - it's also a lot cheaper. I find that with Forte V VC fiber, exposures are longer than they ever were with graded papers (Ilford, Seagull, and others over the years). I have no direct comparisons, but I think about 2 stops longer, for a small print, probably longer for a large print due to RF.
A grade 1.5 to 1 (with the Forte paper, LPD 1:2) is probably close to a grade 2 Seagull G-2 graded paper, for me.
One other thing, I bought an extra filter drawer to faciliate swapping filters, especially with burning and dodging.
I also had to rig up some felt gasketting and a large 4" wide elastic band (some stuff from the fabric shop made for elastic beltlines on pants) wrapped around the head to plug up all the leaks. But I love the results with this paper and Selenium toner.
If you want to know more about my experience with this setup, PM me.
Flipping through old magazines, I came across a blurb in the August 1992 issue of Camera and Darkroom for the Stouffer S/L 1 timer that functioned in both seconds and logarithmic modes. Nowhere in the blurb does the term "f-stop" appear. It listed for $625.
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Ooh, an article on F-Stop Timing in the March, 1991 issue...