Durst Laborator 1200 VLS 501 head

RalphLambrecht said:

It's unlikely to help. On the other hand, as Marco says, I might be too picky. After all, I optimize print exposure to 1/12 f/stop and print contrast to 1/4 (sometimes 1/8) grade. To me, any larger of a difference and the print screams for help. Others may be more tolerant.

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Ralph, I don't think you are necessarily "to picky", your prints are testimony to the the high quality you achieve through your working methods, however, I do think most people like you say will be more tolerant, and just not experienced enough to get near this level of control.

Although I consider myself now a quite experienced printer, I certainly don't see myself capable at this moment to achieve similar control (at least not until I bought and read your book from page 0 to 580 ).

Your remarks about these small tolerances (1/12 F stop, 1/4 grade contrast) do raise another question though: how do you deal with developer exhaustion / use during a printing session?

From experience, the developer starts working more "soft" when it gets older / is used. Now I assume you start out with fresh developer for each printing section. I can't afford that luxury, and store&re-use whenever possible, especially since most printing sessions are relatively short. I do keep a close watch on activity and total use though and store in full stoppered bottles.

But even starting with fresh developer each session, you still have a change in contrast with use, that is probably going to exceed your limits.

Or am I right to assume that this change is actually independent from the exposure changes in your exposure compensation tables? As you probably make a test strip on the chosen contrast, any change necessary to contrast, will be done based on that evaluation, and exposure compensation is applied just as normal... Meaning although with fresh developer you might use grade 2 for the final print, the same print printed at the end of a printing session, might require and get grade 2.5?? :confused:

Well, I guess the answer is going to be that you mix up fresh developer from scratch from powdered chemicals just before each session, and refresh so frequently so as to never even get near any sign of developer use or exhaustion...

ic-racer said:

A table or enlarger head that pivots on such a high value would be non-intutitive. As contrast changes are commonly changes that make darks darker and lights lighter without overall impression of the print being darker or lighter. If you are keeping the lighter values constant then the overall print will look darker or lighter as contrast changes. That does not satisfy the common impression of a 'constant exposure' system. ...

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Well, that's exactly the point. I don't want a contrast change that changes tonal values at both ends. I want exposure to only control the highlights and contrast changes to contol the shadows (and only the shadows). That is what this table achieves. That's very intuitive in my mind. Juggling highlight and shadow changes whenever contrast is optimized is too confusing to me.

By the way, contrast filters do the same thing. Their makers just picked a different common point (0.6>b+f). Whenever you want a 'constant exposure system' you need to pick a constant target density. Selecting a highlight point makes things a lot easier and avoids the need to bounce back and forth between exposure and contrast modifications.

It's the way I learned printing from Howard Bond and John Sexton. It works well for me. Others may have a different approach.

Marco B said:

... Your remarks about these small tolerances (1/12 F stop, 1/4 grade contrast) do raise another question though: how do you deal with developer exhaustion / use during a printing session? ...

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The answer is called 'factorial development'. It takes care of developer exhaustion and temperature fluctuations.

RalphLambrecht said:

Selecting a highlight point makes things a lot easier ...It works well for me. Others may have a different approach.

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Yes, and indeed it may be good for novices also. It just seemed a novice reading this thread could be confused. One needs to understand that in that system, the test prints need to be selected that have the correct highlight value when the exposure system pivots on the higher values. And, as pointed out, that exposure system needs to be created from scratch by the user.

None of the commercially produced constant exposure heads or constant exposure filter systems function that way.

ic-racer said:

Yes, and indeed it may be good for novices also. It just seemed a novice reading this thread could be confused. One needs to understand that in that system, the test prints need to be selected that have the correct highlight value when the exposure system pivots on the higher values. And, as pointed out, that exposure system needs to be created from scratch by the user.

None of the commercially produced constant exposure heads or constant exposure filter systems function that way.

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Correct, except for the products from RHDesigns, such as the Analyzer for example, but you are right, they are the only ones I know of. One possible reason is that the system is easy to execute manually, but much harder to automate due to the non-linear variances in papers. The Analyzer works this way by calibrating each paper once. It's the same thing as making oneself the table for manual exposure compensation.

RalphLambrecht said:

The answer is called 'factorial development'. It takes care of developer exhaustion and temperature fluctuations.

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Ralph, I need to get your book... but could you briefly explain what "factorial development" means, despite quite some years here on APUG it is the first time I see the term used, so I haven't got a clue

Marco B said:

Ralph, I need to get your book... but could you briefly explain what "factorial development" means, despite quite some years here on APUG it is the first time I see the term used, so I haven't got a clue

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Factorial development is based on the assumption that all print densities emerge proportionally in the development bath. In other words, the time of emergence for any particular image tone is a fixed percentage of the total print development time. If, for example, it takes 20 seconds for the midtones to appear in a print that is fully developed after 2 minutes, then it will take 3 minutes to fully develop the same print in another developing bath in which the midtones emerge in 30 seconds. In practice, factorial development relies on the photographer noting the emergence time for a specific image tone in the developing bath and multiplying this time by a development factor to determine the total print developing time.
Once established, development factors are constant and do not change with developer activity. When using fresh developer, for instance, the emergence time is short and so is the total development time. Advancing toward developer exhaustion, the emergence time increases, but so does the total development time. The case is similar for changes in developer activity due to temperature fluctuations. Nevertheless, the ratio between total development time and time of emergence for a specific image tone remains constant. This so-called development factor can be used to compensate for any change in developer activity until the developer approaches exhaustion.

Many usefull tips! Thanks!
But i'm asking if there is anybody that use that kind of head (DUSRT VLS 501) because i don't understand if is normal that, with "Automatic" filtration inserted, from grade 2 to grade 5 the choosen exposure time reduced about by an half! It's so! Someone has this head?
For example: if i find a correct exposure time after test strip in 10 sec. with the selected grade "2,5"........and then i setup filtration of the head for grade "5" the exposure time will change in about 5,5-6 sec! Time is reduced of abuot 4,5-4 sec.
While if use the "Manual" position on the head (read: automatic diaphram not inserted) the exposure time obviously grow up progressively, like, i think, is normal with the magenta filter insertion that reduce the quantity of light reaching paper.
Apart all the things you said me, i want to know if the filtration is broken or not so i need a feedback from users of this head that could tell me how their head work if they have one.......then i could make every things you suggest like te "exposure compensation table" or "trials and errors"...and so on: i'm a young printer but i often use read Ansel Adams's books!!!!! My Holy Bible!!!!
regards

Hello !
Something must be wired in reverse !
All VC paper I know of are half as sensitive in grade #5 than they are on the lower grade (00 to 3 and a half) So the exposure should double when you dial the grade #5 !
The blades should open instead of closing.
But maybe the light output of the head is increased in a way or another ???
IMHO, read my post about making a print, try it, then redo a test going to full grade 5 and see if the print exposure are consistent. You'll know !
My printing method explained above is actually not mine, it came from what I learn from more experienced people like Tim Rudman, Ralph Lambrecht, etc... And is consistent with what Ralph wrote above and the software embedded in the RH Design Analyser Pro.
I urge you to make such a trial. You"ll chek in a couple of print if the whole system is working, usable, faulty or fool.

GeorgesGiralt said:

.....
The blades should open instead of closing.
But maybe the light output of the head is increased in a way or another ???
.....

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YES, is so....thanks to progressive aperture of the blades whith magenta filter insertion.....but the blades open too much????

ciccioder said:

YES, is so....thanks to progressive aperture of the blades whith magenta filter insertion.....but the blades open too much????

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I do, like you asked, urge Durst VLS 501 head users to step in again with this thread to give their opinion, as that may give a better idea of potential problems.

However, another issue here is that we have at least two variables intermingled: your paper and the head. Unless you know the characteristics of your paper, and how that compares to the paper the VLS 501 head was calibrated to, it will be difficult to answer your question about a potential issue.

I do think it would be useful if you told us the exact paper you are using, because I think I did not yet see it reported here by you in the thread (e.g. "Ilford MGIV FB Glossy", "Ilford MGIV RC Deluxe"). Maybe Ralph, with his vast experience and knowledge of these papers, can than give a better judgement about your observations and if the printing times at grade 5 are "unusual"...

It may also be useful to have a look at the paper characteristics as listed by the manufacturer. Usually, you get an information sheet with each package, or otherwise it is on their website.

Edit: realized Ralph wrote somewhere he has 2 papers as his main stock. Well, with all the other users around here, someone might be able to comment on your stock, even if it is less common.

There might be someting wrong in your head.
When dialing from grade 2.5 to grade 5, the exposure time should be the same.
An ND filter is automatically added or substracted when changing the grade.
It is an mechanic process, maybe you can open the head and check what is wrong.
When you turn the handle that is changing grades a fliter (or filters) must be moving.
If read your story it could be that the ND filter is stuck somewhere.
From grade 2.5 to grade 5 yellow filter will disapear, magenta is added more and more ND is added.

Mike.

i just open the head and it seems to be normal: Y/M filter insertion is correct and the blades move regular under the filters...but i dont't know if open too much, i can't mesure it...it's mechanical.
With the Compolux (durst's anlayzer to find exposure time and grade of paper!!!) i notice a strange things.
i will try to explain so you can say what you think about:
i turn on the enlarger with or without a negative inserted (is not important) and place the compolux under the light in measuring function; after that, while the analyzer is measuring, i rotate the knob of the grade and i notice that you have the longer time at grade 2,5 and WL (it's normal because in this position there is just a bit of magenta filter insertion and the blades under the filter let pass poor light, are almost closed); if you rotate the knob from grade 2,5 to 5 the exposure time began to go down (so!) in a proportional way (or it seems so) and i'm trying understand whath is this factor....yesterday the measuremet was
grade - seconds
2,5 - 15,2 sec
3,0 - 12,7 sec
3,5 - 10,6 sec
4,0 - 8,6 sec
4,5 - 7,2 sec
5,0 - 6,8 sec
it seems that i have to sottract a 0,15 of the precedent exposure....
from grade 2,5 to 2 the light go down slightly of another 0,5 and remain constant on grade 1,5 - 1 - 0.5 and slightly go down of another 0,15 on grade 0.
naturally as indicate by the analyzer....but i tried make some print and, apart some manual little corrections of the exposure time, the print, according to grade you choose, are good: are a good starting point!
The problem is that in this way if i don't understand the factor i have to reduce the exposure time i have to re-measure the light and in mesurement mode i have to rotate the knob of the grade to the new grade choosen!
i'm not sure of my explanation, if was clear....but is so!!!!
as indicated an exposure compensation table could help me but it's not clear how i have to do it.....really!
i don't know if as i read on the forum it depends from the fact that the head was calibrated for another paper (now we are speaking about the use of the new Ilford Multigrade RC Deluxe 44M) or if it's broken....i want to know from another user that has the same head if my head is woking well, if is normal the reduction of the exposure time of y head....
regards

Ciccioder,

You say that you made a print that has a good starting point.
What if you use the same exposure time and only change the grade, the print should have the "correct" exposure time and only the normal grade changes should be visible.

It could be that the Compulux is misleading you.

Mike

No, the compolux help me...it measure density...so i have the correct time...and if you set it could very accurate.

In the past I had a VLS501. As Ralph already stated the automatic function is not that helpful as you may think.
But here some remarks as I remember them.

Somewhere on the head there was a insignia clarifying for which paper it was calibrated.

You can test it's function through printing a stepwedge in grade 5. Expose so that a step somewhere in the middle on the print has a density of D=70-75. Compare with a medium grey card. Without changing the print time, make prints with other grades. The density of the field you set to middle gray, if your head is working al right will be the same in all prints.

Gary, many tahnks, but why i have to start from grade 5 and not for example from grade 2 or 2,5? There is a specific reason that i don't understand?

A grade 5 will give a higher precision of your exposion time then lower grades.