Entering a new era - getting stabilized light

[Bill Burk]

Not long after I started out, I got a voltage stabilizer for my Omega D condenser head.

It made a big difference in my mind, freeing me from concerns about voltage drift and boosted my confidence.

That lasted as long as the condenser head made me happy, then I found I needed cold-light and switched to the Omegalite-D.

The unstabilized light frustrated me, I dealt with it best I could but finally got things under control when I started using this...

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Later I got frustrated with the ring light's "hot spots" which would show on every print, that went undetected until I started putting prints on the computer. Then the pattern became so apparent that I switched to an Aristo Grid light.

I put a similar sensor into the Aristo Grid and have been using the setup for a few years now. It works as I designed it, but requires a specialized skill set that I don't think anybody would want to acquire: I turn it on and wait until the readings settle (around 500K-ohms) before I print. I write down numbers every few seconds while I am printing, to record the brightness of the light over time (in case a print comes out wrong). If the numbers are high (less light) I'll manually add a few seconds, if the numbers are low (brighter light) I'll block the light early. And I turn on the lamp while the previous print is in the fixer... to warm the lamp up to operating temperature.

It's quite an elaborate ritual I've had to work into my darkroom printing process. It's a bit "left-brained" during an operation that should be "right-brained"... But it works.

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Until now... Greg Davis sold me this stabilized light source, something I've been "desperately" wanting, ever since reading about it in Zone VI newsletters.

Once I get this installed and operating, I will be able to completely forget about light intensity variation. I am looking forward to this!

I already have my developing controlled by a compensating timer, and I thoroughly enjoy being able to forget about temperature variation. I know how much I am going to enjoy this new era.

 

[Bill Burk]

I forgot to mention... this might be the real deal, or it just might be a silver bullet chase.

I don't know which yet.

 

[analoguey]

Question - are you saying voltage stabilizer only helped with condenser head, not so with the cold lights?
(not quite familiar w trade names)

Sent from Tap-a-talk

 

[Bill Burk]

That's right, with an incandescent bulb, the brightness varies directly with voltage.

With a cold-light the brightness varies with operating temperature, there is quite a dance of light output over time.

It goes like this: Not so bright when cold, levels out after warm (good after just a few minutes), dims when hot.

You can overcome most of the issues by "working" when the light output has stabilized, after a warmup period and before it gets too hot. I was doing that the hard way.

 

[analoguey]

I see, hmm. Afaik tungsten also is dependent on temperature(filament's) -which is a fn of voltage?
Is the cold light a 'noble gas' based concept - Something like the tubelights? Or are these on a diff principle?

(my only exp with stabilizers is with tv/fridge -so hope you mind the questions)

So now you can retain temperature correctly?

Sent from Tap-a-talk

 

[Bill Burk]

Oh, right. Yes "grid" describes the tight zig-zag configuration of the folded tube. It's a fluorescent bulb.

It's "also" a function of voltage.

The design of the gadget Greg sold me... Monitors the light output and adjusts the voltage to hold a steady light output.

 

[snapguy]

For some reason

For some strange reason I feel an urge to refer you to the Laurel & Hardy Oscar-winning short film "The Music Box." It is an intellectual piece of cinematic art concerning doing things the hard way.

 

[analoguey]

Ah. Output based regulator -thats nice! So there's a feedback loop somewhere. (now I get the bit about resistors)

Do you have a diagram of your earlier set-up?

Sent from Tap-a-talk

 

[Bill Burk]

Yes the Zone VI unit has a feedback circuit. Should be nice.

My old unit needs no diagram. The CdS sensor connects directly to the Ohm meter, and I just read off ohms while I'm using it.

snapguy,

That's funny, my friends used to point out that stairway as we drove visitors on tours around Los Angeles...

 

[Sal Santamaura]

Compared to what you've been dealing with, it will indeed be a huge improvement. Not perfect, however.

First, you'll still have falloff in the corners that requires burning. Second, with its single diffuser, you'll probably be able to see the tube's serpentine pattern, but only when printing images that include large areas of even tone.

The only way to overcome these shortcomings is with an oversize light source and double diffusers. As Fred Picker concluded. Which is why he designed the Zone VI enlargers thusly.

 

[Bill Burk]

Thanks Sal!

Glad you mentioned it won't be perfect. I'll get prepared to burn corners.

 

[NedL]

Hi Bill,

The sensor in my old zone vi cold light is a photodiode. It's interesting what you wrote about "left brain" "right brain" during printing. After monitoring the behavior of my cold lamp, I start my timing in the "stable" part of the curve.

I was originally going to set up a monitor like you've been using, but have found that I can replicate a print so that I can't see the difference without it. For now, for me, that's all that matters. But my choice not to go further was mostly driven by not wanting to over-complicate or distract myself... your left v right comment.

Good luck with your new setup and I hope it works great!

Ned

 

[Bill Burk]

I think you're right NedL,

The greatest value I got from seeing the numbers... was being able to get a feel for the rituals that were necessary to work while the numbers were stable. So I got to know how long it takes to warm up, and when it was getting too hot.

 

[palewin]

Just a heads-up: with the ZoneVI stabilized heads, you still have to keep them in the operating temperature range. My standard procedure is to flip the enlarger onto "focus" once I have my print in the fixer, so that the head is stable for my next print. If you simply turn the enlarger on when you are ready to print, you will find that it takes time to re-stabilize before its ready to use. On the ZoneVI heads (at least the VC head I have installed), you know it is stable when the green light stays on during exposure.

 

[Bill Burk]

Thanks palewin,

I did kind of expect to have to follow a similar "ritual" of turning it on for a couple minutes while the previous print is in the fix... I figure I want that green light to come on within a second or two...

 

[Peter Schrager]

Bill..I was caught up in the zone VI "cycle" for many years. I had all the timers and stabilizers; lights etc. Now I just use the developing timer without the probe. It was and is a magic bullet chase. I make up to 15 identical prints during a session all without the use of any of the above. good luck but just learn to be a good printer and the rest comes naturally!!
best,peter

 

[john_s]

The old Zone VI cold light head needed the Stabilizer to even out the fluctuation in light output when the lamp warmed up. (In this context "cold" light was a misnomer) The downside was that to get a stable output the light was limited to a fairly low output. Using the 4x5 lamp to do 35mm negs it was faint, and a drag for big prints. In other words, it clipped the peaks so all you had was the level of the troughs.

Then Zone VI introduced the Compensating Timer, so the lamp went full intensity and the time was adjusted to compensate. It clicked with every nominal "second" and the acceleration in clicks as it warmed up was dramatic.

I now use an Aristo VCL4500 and an RH Vario, working on the same principle but with better ergonomics. Interestingly, the two tubes don't change in intensity nearly as much as the old one did, and the Vario takes account of the variation anyway.

Aristo have been taken over and but the new company will make tubes to order. Not cheap, but if you like the system as much as I do it's worth it. The newer tubes for the single tube Zone VI/Aristo heads is supposed to have a wider spectrum making the use of filters for VC paper better (better spacing, better low contrast performance). I wonder if these newer tubes might exhibit less temp/output variation. Just conjecture.

Contact details in this thread. Thanks to Ken Nadvornick for bringing this to our attention. Some links below, and there is another post

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And if you want a spare sensor, see:

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[Bill Burk]

Thanks Peter Schrager,

You are probably right. I can make perfectly fine prints with my current setup.

I do like my developing timer (not Zone VI but virtual clone of it) and use the probe. It makes my darkroom setup faster as I no longer check for "exactly 68-degrees". I expect this stabilizer might have similar benefit for me.

 

[DREW WILEY]

Just get some ole graphics gadget "light integrator". That was basically all the Zone Six compensating metronome was, with a probe and beeper. Probe placement is crucial. Then cold light often need some kind of warmer to get them jump started. Other than that, trying to tame them and make them perfectly consistent is like trying to teach a rhinoceros how to dance on its hind legs. Cold lights are what they are, and vary not only with temperature and voltage fluctuations, but with age, the exact curl of the loop, etc etc. No sense fighting it. The Z6 compensating gadget just ignored all of that and did exactly what it claimed to do. There have been other makers of such things.

 

[MartinP]

I noticed this link with some interest as I'm considering ways to build my own camera/enlarger currently. This is not due to me searching technical perfection in enlarger design, but just because the available supply of the equipment here is negligible at a sane price. Nevertheless, if the light output from an oversized, high-quality unit really is even and bright perhaps an oversized lightbox could replace an unreliable cold-light ?

 

[DREW WILEY]

People have devised various alternatives to cold lights (as opposed to "hot" halogen colorheads). Salthill used a big fiber optic bundle to evenly
distribute cool light to the diffuser. Various people at the moment are trying to adapt LED panels in lieu of cold lights, which should work for ordinary black and white applications with intelligent prototyping, but color printing LED applications seem rather premature at this point in time. I'd be a bit wary of old used cold lights or with ones which ONLY cover their intended format (they do need to be conspicuously bigger and preferably brighter than the minimum requirement). But given a good unit, I think the complaints about cold lights are real, but overstated at times, and easily overcome in routine usage.

 

[Bill Burk]

Got the lamp today, fits right into the old housing where my old Aristo grid used to go. So I didn't have to do any metalwork. It stabilizes almost immediately at the lower settings. But, as expected (thanks for the tip john_s), the higher settings don't stabilize. My standard print size is 11x14 and so I will soon find out if one of the lower settings gives me approximately 30 seconds print time (my preferred print time).

If I get 30 second print times with one of the stabilized settings, I will be very happy with the setup.

 

[john_s]

...the higher settings don't stabilize......

You can get somewhat higher settings to stabilize if you leave the lamp on for a little while. There's a full (FOCUS) setting isn't there? It's been a while and I can't remember. Sometimes even 5 or 10 seconds can help. You are using the heating circuit I suppose. It didn't seem to make a huge difference, but my darkroom was fairly warm, maybe that's the reason.

 

[Bill Burk]

Right, I left it on for a while and after a couple minutes more settings would stabilize.

I also "tried" the heater circuit and didn't notice much difference, it gives me maybe 2 additional available options.

 

[MartinP]

Isn't a coldlight head usually used with a shutter under/on top the enlarger lens? Am I misunderstanding the "leave the lamp on" problem - surely it can't run directly of the timer?