Question and Observations using a Zone VI VC head.

I've become quite intimate with my Enlarger over the last few months, and have discovered a few interesting things. Have other users found the same?

Just to clarify things......

I'm using the VC head, with the Z6 controller, zone vi compensating timer, and the darkroom temp is usually about 60 degrees. Hey, it's cold in the winter.

I've also been reading that if you have a stabilized light source, (as this head is), a compensating timer is not necessary????? I can tell the compensating timer is working.....As evidenced by the "time" it takes with the blue vs. the green.

I've also read that many people say an x second exposure with the green and an x second exposure with the blue will be equal to doing them together at the same time. Perhaps true with under the lens filters and a different light source?
But this can not be true with this head/timer combo....As the "time" settings are relative depending on the light output. 5 seconds on the timer can be closer to 15 seconds of real time with just the blue... Have other users found this to be the case??

The intensity of the green light is almost 2 stops brighter than the blue.....After digging out the good 'ole Ilford EM10 that was confirmed.

It is next to impossible to get the green stabilized light to appear if the brightness is cranked all the way up. (when using just the green).

It will stabilize must faster with the blue light vs. the green. And of course, the brighter it is, the longer it takes.

After waiting sometimes like 30 seconds for it to "stabilize", I've taken measurements and the light doesn't seem to change at all when waiting for the little green light to appear!! So I'm surmising it is not that important to wait for the light? Anyone else find this to be true??

As to the intensity, the green is so much more powerful than the blue, the light output varies very little from just green vs. green combined with all blue......weird...

When using the controller, is max green supposed to equal 0 or 00 and max blue supposed to equal 4 or 5?

If both knobs are set to max, or equal settings is the contrast supposedly to be normal, or approximately grade 2?

So, any of this make sense? Do I have a weak blue tube? Or is it normal behavior for this head?


OK, I understand this post contains plenty of observations and questions....(hey, at least my subject is accurate).

Hi,
As you may know paper grades aren't absolute across paper brand and light soure. For me with Ilford Multigrade both knobs turned all the way up is grade 2 but other papers will vary. Get yourself a Stouffer 21 step density tablet that fits your negative carrier, and a copy of "The Variable Contrast Printing Manual" which will explain how you can test for contrast settings. Also this thread: www.apug.org/forums/forum41/34364-zone-vi-variable-contrast-head-test.html
Mark

When I was testing Ilford MG paper to filtered light I found it about 2 stops more sensitive to blue than green. Now who is to say my filters were 'equal' but, in general the paper will be more sensitive to the blue light. So, maybe it is supposed to be that way; that is, the blue light is supposed to be dimmer than the green to match the paper sensitivity. Just a guess.

Your post is a good reminder to me why I drove nearly 600 miles over 3 days to get a dichroic halogen light head source to replace my coldlight head

Thanks for the reply.

What I'm really wondering, is the head supposed to give the same, (normal) contrast if both tubes are set to the same brightness level....Or in the case of the Z6 controller, both set to the same "letter". Was/Is that the intended operation for the head? Just trying to figure out how it is supposed to work!!

Very interesting........so, if it is more sensitive to blue light, it is less sensitive to magenta?? Since VC papers are "slower" with the high grades, yet are "faster" with the blue light??

But that doesn't explain why with the timer gives a much longer unit of time with the blue light vs. the green.

I'm not sold on this head...Yet it does provide for relatively easy split printing.....

I had the Zone VI VC cold light for 4x5 connected to an RH Designs Vario timer.

I found it frustrating to use because the timer varied so much when changing the filtration.

Using a regular cold light with filters or a dichroic head works better for me.

I am not familiar with your light source but I use an Aristo grid VCL4500 that has several combinations and you can dial in contrasts. I recall from some Fred Picker (Zone VI) literature that the compensating time had to do wit dry down changes in the print. You may be able to track down some of his books.

tequilabong said:

Thanks for the reply.

What I'm really wondering, is the head supposed to give the same, (normal) contrast if both tubes are set to the same brightness level....Or in the case of the Z6 controller, both set to the same "letter".

Click to expand...

The letters for the dials are merely for your own notetaking as to how much you've dimmed each color light, if any. Since papers respond to green and blue lights differently there's no way to ensure, say, green=F/blue=F is the same contrast as green=C/blue=C, only dimmer.

You might as well leave the center dial (brightness) on max all the time and control brightness with aperture. To set contrast, you always have green or blue (or both) on maximum. Do testing to see the effect of reducing only blue to soften contrast (tending toward pure green), or reducing only green to increase contrast (tending toward pure blue). There's no reason to not have at least one of the colors on maximum to maximize light output on this slow head.

Hope this helps, and others correct me if I've missed something!

Mark

As to the compensating function, it is not for drydown. There is a separate control for drydown. The brightness knob was more of a function that will speed up the "stabilize function"....Of course I'd like to have it all the way up, but it never seems to "stabilize" with it at full brightness.

When I split print, the tubes are always set at max....

jeroldharter said:

I had the Zone VI VC cold light for 4x5 connected to an RH Designs Vario timer.

I found it frustrating to use because the timer varied so much when changing the filtration.

Is not that the intended purpose of a compensating timer?
It compensates for the changes in light output?? Or am I missing something??

Using a regular cold light with filters or a dichroic head works better for me.

Click to expand...

Do you still have the vario???

I've been exploring this light source as well. I've found that setting the "hard" and "soft" dials to the same setting no matter what level gives me the same contrast but with less brightness. I don't know if this is what it is supposed to do or not. Last night I experimented with just playing with the "soft" control. If you set the "soft" dial up like from "E" to "G" the black tones get lighter in the print. The white tones stay the same which of course equals less contrast. I can see this only controls contrast and not the "scale" of the print. Scale would have to be controlled by dodging and burning. Contrast is better thought of as the difference between one tone and the next not to how dark the dark tones are and how white the white ones are. If you think of the contrast as "local" and the over all scale as something else it starts to make sense. I've often thought that calling both the local and the overall subject or negative density both as "contrast" is confusing as they really are not the same thing. I'm still learning this head. I'll keep looking at this thread.
JOHN

I think these 'additive' heads were made for a freestyle printing technique where you 'ride the dials' to get your print without being concerned with 'paper grade.'
So the blue knob controls shadow density and the green knob controls highlight density.

So, make a test print and spin the knobs up or down depending on if you want more or less shadow density or more or less highlight density in the print.

You could calibrate it like one would calibrate a dichroic head using the scales on the knobs and a step wedge and make a table of constant exposure settings but if I had one I'd try to learn that freestyle technique.

Oh, also. Becoming "intimate" with your enlarger is the best thing you can do to imporve print quality. The enlarging process is the single most important thing for print quality. How far is the light source from the negative and what effect does that have? How bright is the source and how does that effect the flare of the lens? Can you balance the flare factor with the choice of f stop? How large is the print? Knowing the answer to these and a lot of other questions can help a lot and can give you more choices on tools to make the print the way you want it to be.
JOHN

Here are the settings I use with Zone VI heads and Ilford Multigrade IV -- your results may vary (soft setting is first/hard setting is second):

Grade 0 = Max/Min
Grade 1 = Max/E
Grade 2 = E/E
Grade 3 = D/Max
Grade 4 = B/Max
Grade 5 = Off/Max


These were established by testing and using the BTZS software. There are testing procedures in Steve Anchell's variable contrast book as well.

As others have said, equal settings for the soft and hard lights should yield Grade 2. I use E/E because it is in the middle of the range and I can easily tweak the contrast up or down with each control.

I have a zone vi type i enlarger with the variable contrast head and have similar experiences.

I'm not sure if the soft tube is failing somehow, but setting the controls to Max/Max (or any equal settings) does not give me a grade 2. Depending on the paper, it is more like Max/A.

I contacted Aristo a while back about replacement tubes but they wanted $1000.

Rob

Rob, did you tell you just wanted one, not an entire case? Dang, that supply and demand thing really sucks sometimes . . . espescially when you are on the demand side of the equation. I'm looking for an out of print book which sold for $29.95 when new and they are selling for about 4 times that now. Guess I'd better start looking for my replacement tubes now, before I need them. Bill Barber

nsurit said:

Rob, did you tell you just wanted one, not an entire case? Dang, that supply and demand thing really sucks sometimes . . . espescially when you are on the demand side of the equation. I'm looking for an out of print book which sold for $29.95 when new and they are selling for about 4 times that now. Guess I'd better start looking for my replacement tubes now, before I need them. Bill Barber

Click to expand...

To be fair, they were going to have to custom-make the tubes to fit into the enlarger head. Still pretty steep.