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  1. #1

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    Durst Laborator 1200 VLS 501 head

    Hi, i'm new on he forum, and i have to submit a question:

    i early buy the enlarger in object with VLS 501 Head and i don't understand if when i change the contrast i have to change even the exposure time.

    Quiet stand up to the time, I used it without dichroic filter inserted, but now i'm using VC papers, so that this function of the head could be usefull.

    My problem is that when i make test strip at WL (white light) and than choose exposure time, if i change contrast, my print becames too darker: it's like the internal diaphram lets pass too much light (when is inserted - Automatik position).
    I don't understan if i make some mistake calculating exposure time or if is a problem of the Head of the enlarger.....i've read that the head could change contrast without modify exposure time but in my case it isn't so!!!

    Someone could help me, please? i've red some post on the forum, but none explain well the head functioning.

    regards

  2. #2
    paul_c5x4's Avatar
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    You need to make a test strip with the filters in place, not under white light (WL). With the filters in place, changing the grade should not affect the required exposure unless you want grade 0 or grade 5. The data sheets that came with the paper should tell you if the exposure needs changing at higher grades (or lower).

  3. #3

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    But are we speaking about the DURST VLS 501 HEAD?
    Anyway: i have to do a test strip with choosen filter, not at WL, then, after i have choose the "correct exposure time", if i choose a different grade, the head will automatically vary the quantity of light for correct exposure with the new filter?
    And why not i have to do a test strip at WL?
    It's not as the same things as i do that with any other filters?

    thanks
    Last edited by ciccioder; 10-11-2010 at 10:54 AM. Click to view previous post history.

  4. #4
    RalphLambrecht's Avatar
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    You need to make yourself a table such as the graph attached.

    You'll find how to make it here:

    http://www.darkroomagic.com/DarkroomMagic/Darkroom.html

    Scroll down to 'Paper exposure Compensation'.
    Attached Thumbnails Attached Thumbnails PaperExpTable.jpg  
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  5. #5

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    Sorry, but i don't still understand.....the DURST VLS 501 HEAD should automatically change the quantity of light when you change the grade....or i'm wrong?
    why i have to do myself a table if the head make the work alone automatically?
    Last edited by ciccioder; 10-11-2010 at 03:12 PM. Click to view previous post history.

  6. #6
    mhulsman's Avatar
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    The VLS 501 head does automatically change the amount of light according to the grade.
    So if you have a correct exposure time for grade 00, you can use the same exposure time for grade 5
    from the manual:
    * DURST VLS 501
    Diffused illumination systen for black and white
    enlarging using variable contrast papers
    The contrast is continuously adjusted with a control knob.
    The system provides also automatic density compensation
    But when you start the initial exposure time do not use the handle in "white Light" position.

    I made a set of all grades starting from 00 until 5 with 0,5 step grades.
    That will give you a nice overview of all the grades the head can give you, and you can test if the density compensation is working.

    Regards.
    Mike
    --Mike

  7. #7
    RalphLambrecht's Avatar
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    Quote Originally Posted by ciccioder View Post
    Sorry, but i don't still understand.....the DURST VLS 501 HEAD should automatically change the quantity of light when you change the grade. ...
    How could it possibly do that?

    How does the VLS 501 know what paper you're using, and how does it know which print tone you would like to keep consistent?

    It simply doesn't.

    Sorry, there is no such thing as automatic exposure compensation with contrast changes. You need to run a test and record it in a table for future work.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  8. #8
    RalphLambrecht's Avatar
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    Quote Originally Posted by mhulsman View Post
    The VLS 501 head does automatically change the amount of light according to the grade. ...
    Unfortunately impossible. The advertising claim is referring to the, so-called, speed point, which is part of the ISO standard but has little in common with actual printing practise. The exposure compensation required for contrast changes differs with paper and target tonality. Of course, the VLS 501 is unaware of both.

    One can read similar claims about contrast filter sets, but those claims are misleading too. It only works if you want to keep the speed-point density consistent, and who wants to do that?
    Attached Thumbnails Attached Thumbnails PaperSpeedPoint.jpg  
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  9. #9
    Marco B's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    Unfortunately impossible. The advertising claim is referring to the, so-called, speed point, which is part of the ISO standard but has little in common with actual printing practise. The exposure compensation required for contrast changes differs with paper and target tonality. Of course, the VLS 501 is unaware of both.

    One can read similar claims about contrast filter sets, but those claims are misleading too. It only works if you want to keep the speed-point density consistent, and who wants to do that?
    Ralph: while your answers are technically true, for most "ordinary" darkroom workers like myself that do not "fine-tune" our printing practices in every detail, the automatic "compensation" of some of these systems (I have Ilford's 500H Multigrade head), does offer a good starting point, and I think most people will make any exposure adjustments in a more relaxed and unconscious way by thinking:

    "Oooh, I changed the grade from 2.5 to 3 and now it looks to dark! Got to take off a few seconds! "

    instead of consulting "tables" each time they do an adjustment.

    At least, that is how I partly find my way to the final print...

    While I admire your attention to detail, and your book is still hot on my list of "things to get" , it is not the only way to look upon this.
    Last edited by Marco B; 10-11-2010 at 05:16 PM. Click to view previous post history.
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  10. #10
    Marco B's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    The exposure compensation required for contrast changes differs with paper and target tonality. Of course, the VLS 501 is unaware of both.
    Actually, interestingly, looking at the manual of my Ilford 500H Multigrade head, it says it was specifically designed for one specific paper: Ilford Multigrade II VC.

    So, in a sense, it does know at least one paper , but I don't know how modern papers compare to that old Multigrade II version.

    In addition, the light output of the lamps is microprocessor controlled, and it literally says:

    "Once the exposure is established at a particular contrast level, the Ilfospeed Multigrade 500C control unit adjusts automatically the intensity of light to ensure exposure times remain the same right across the contrast range"
    (0-5 for the unit)

    However, the old control unit is not sophisticated enough to be able to "store" compensation data for multiple new papers. I guess that with a modern day unit of RH Design or so, you will be able to store it all, but I haven't had a good look at it all. As long as it all keeps working, I will stick with what I have now.
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

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