Enlarger too bright (Durst CLS450)

Discussion in 'Darkroom Equipment' started by henpe, Jan 20, 2018.

  1. henpe

    henpe Subscriber

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    I have a Durst Laborator 1200 with CLS450 color head that I find is too bright. Two or three stops down on the lens (f/8-f/11), I get down to exposure times of just a few seconds. What is the best practice to reduce light output?
    1) Stop down the lens? How about diffraction? For right or wrong, I am not comfortable going smaller than f/11 due to diffraction.
    2) Replace the bulb. I currently have a 250W bulb and it seems there is also a 200W bulb for this socket and voltage (Gx5.3/24V). How much difference would that make? If light-output is approx linear with power, I would only loose 20% which is about 1/3 of a stop, not that much.
    3) ND filter seems like a solution, but I generally don't like the idea of putting a filter under the lens.
    4) Some other solution? Can I modify the enlarger head or enlarger somehow?

    Anyone else who has had this problem and found a good solution? All input is welcome!
     
  2. Fritzthecat

    Fritzthecat Member

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    you can do any of those things or do what I do, expose for denser negatives.
     
  3. chip j

    chip j Subscriber

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    Hook up a dimmer switch--that's what I have on my Durst M35 Micromat--cheap.
     
  4. Chan Tran

    Chan Tran Member

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    May be remove you diffuser and see if you can modify it to make it darker.
     
  5. Johnkpap

    Johnkpap Member

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    I have a L1200 with a CLS500 head the first question, what mixing box are you using and what size negative and what print size are you trying to expose?
    All three of these variables will affect the light output.and in doing so affect the exposure time.

    One way is to dial in extra filtration......ADD in 40M 40Y and 40C as these amounts are the same all they will do is lower the light output, are you using Multi-grade paper ?

    If you are using the M and Y filtration to adjust your grades the you need to work this out before adding extra filtration.

    If you are using actual filters then adding extra filtration is quite easy.

    Another solution is to change the mixing box......for example if you are printing from a 6x7 neg swap the FEMOBOX 69 for the FEMOBOX 450 , this will lower the light output also

    You can also use a lens with a longer focal length eg for 6x6 negs use a 105mm lens

    Johnkpap
     
  6. Lachlan Young

    Lachlan Young Member

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    To reiterate what John says above, use a longer focal length lens & the 4x5 mixing box first, then dial in 30-60cc of all colours to add ND - that's probably all you'll need.

    Ignore the stuff upthread about dimmers, they'll muck up the colour temperature (which will cause problems with MG & colour papers) and don't fiddle with the mixing box if at all possible.
     
  7. pentaxuser

    pentaxuser Subscriber

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    Isn't the key question this: If the OP has the right colour head, the right wattage bulb and diffuser box for this enlarger why isn't everyone with such a set-up experiencing the same problem? A few seconds ( unspecified but presumably less than say,5) seems very short at f11. Surely the set-up wasn't designed to give such short exposures at f11?

    I have no answers or explanation but unless the system is designed to operate on say 100W instead of 250W or has a compensating mechanism inbuilt which allows the standard bulb( apparently 250W) to be retained for say 35mm negs to be printed at as little as 4x6 then either the enlarger is designed solely for big negs at say 5x enlargement and not for smaller negs at small enlargement or there is mechanism to allow longer exposure times or a form of Heath Robinson method is required which suggests that the L1200 has a serious flaw

    pentaxuser
     
  8. Fritzthecat

    Fritzthecat Member

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    How's this for an answer. Today's papers are much faster than when these machines were originally engineered and built. Faster paper emulsion, shorter exposure times.
     
  9. Lachlan Young

    Lachlan Young Member

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    Very simply, it's most likely operator error/ lack of experience. The L-1200 and the DeVere 504 are used routinely by many printers for this sort of stuff without trouble - with an appropriate focal length lens to get a sensible working height & thus exposure - for example, a 6x enlargement or smaller off 35mm will often be much easier to achieve if you use a longer focal length than a 50mm. 250w should not be a problem in terms of exposure time unless the negatives are really thin.
     
  10. Lachlan Young

    Lachlan Young Member

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    If anything, modern papers are effectively about a stop or more slower once the filters are compensated for. Unfiltered, they are faster - the graded emulsions seem to sit halfway between the filtered MG paper speeds and the unfiltered MG paper speeds.

    More to the point, the L-1200 is contemporary with modern emulsions anyway.
     
  11. M Carter

    M Carter Member

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    You can get some ND lighting gel - it's cheap, maybe 6 bucks for a sheet - if there's a place in the light path where it won't affect print sharpness. In a diffusion enlarger, I'd guess anywhere above the neg and diffusion. In a condenser, in the filter slot. Or get a decent quality camera lens ND filter and use it under the lens - just keep it clean.

    Dimming will only work if the bulb isn't some ballasted sort, but it will change the color temp of the bulb which can affect contrast with MC papers I would think - dimming it two stops will make it much warmer, much more orange. But you mention a 24v bulb, so I don't know where you'd dim that circuit. There's a transformer in there somewhere, and dimming from the wall could cause some serious problems I'd assume.

    The focal length advice is good, too - if the lens is close to the paper, short times are to be expected.
     
  12. MattKing

    MattKing Subscriber

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    Changing the focal length won't solve the problem.
    The intensity of the light at the easel is a function of negative to print (not just lens) magnification. While the negative to paper distance may be greater with a longer lens, this will be essentially be offset by the lower magnification of the longer lens.
    The lens may be higher, but the cone of light from it spreads out less quickly, so it ends up being just as bright when it reaches the paper.
    Longer lenses may give you more convenient working height, which can make it more comfortable to print. They also often offer smaller minimum apertures (e.g. f/32 instead of f/16 or f/22) which can help provide longer print times.
    Diffraction issues are probably a wash, because they are related to the actual physical size of the aperture, rather then the f/stop.
    You need to reduce the intensity of light as it hits the negative.
     
  13. OP
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    henpe

    henpe Subscriber

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    Thank you all for your valuable input!

    I realize I forgot to include some information in my original post.
    + 4x5 sheet film negs, printed to 16x11"
    + I am using dual filtration
    + I am using the 4x5 mixing box and a 135mm lens
    + I don't think my negs are too thin. Although I am a self trained amateur, I like to beleieve I have my processing under control and I do check my negs with a densitometer from time to time.
    + I am using Ilfords latest paper 'Classic fb, 1K' (ISO P500, approx ISO P230 if used with dual filtration)

    A good point was made above about paper speeds, I think this might be one explanation to my problem.
    About ND lightning gels, where to get them? Will they stand the heat? I did try to put a resin coated square photographic filter on-top of the mixing chamber, but the plastic melted under the heat from the light-beam.

    Thanks!
     
    Last edited: Jan 21, 2018
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  15. Johnkpap

    Johnkpap Member

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    The first thing to Remember is that you are printing with a color head, when printing color you need to have exposure of approx 10-15 seconds at f8 so that you do not get color shifts.

    The enlarger is doing exactly what it was designed to do ......now to print multigrade we have options first is stop down the lens to f22 or more it won't affect the quality.
    The other option is ND filter in the filter draw or on top of the mixing box, the newer CLS500 that I have has a ND dial built in for this reason.

    You use to be able to buy Kodak ND filters in sheet form but in our funny digital world simple items are sometimes hard to find, try looking at $bay or maybe b&h or your local camera shop if you have one.

    johnkpap
     
  16. Lachlan Young

    Lachlan Young Member

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    OK - it's not the paper speed that's the problem - a great many graded papers were about the same speed or faster. I'd stop down to f16 and if necessary add 30cc of CMY & if that's not enough, f22 might be OK too. Diffraction loss is really not going to be noticeable at f16 with a 3x enlargement off 4x5. The CLS501 head might be worth tracking down as it has a built in ND filter of variable density. Alternatively, you could use the under lens Ilford filters & use the head's filters purely as an ND.
     
  17. pentaxuser

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    So it would appear from the responses that paper speed isn't the problem, neither is a longer lens the cure and the wattage of his bulb is OK. The OP negs and specifications seem fine as well. My conclusion would be that the only built-in feature which works is using a higher f number on the lens. All the rest of the solutions are "work-arounds" using other equipment.

    What would be interesting would be a response from others with the same enlarger set-up about their exposure times with the same conditions as the OP has given us.

    pentaxuser
     
  18. ic-racer

    ic-racer Member

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    f11 is the widest one would print a 4x5 negative. For example a very dense negative. Seems like you are not printing a very dense negative. So, why F11?? If you are new to large format photography, this is a common mistake.
    In many cases, across all formats (Minox to 8x10) an aperture from 5 to 6 mm is optimal.
     
  19. Sirius Glass

    Sirius Glass Subscriber

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    There is nothing wrong with using f/8 or f/11 for printing. I use those stops for both black & white and color enlarging for years. Now if you had to drop to f/22 or f/32 I would be concerned about adding diffusion.
     
  20. pentaxuser

    pentaxuser Subscriber

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    The problem that the OP, henpe, has asked us about is short exposure at f8/11 so what is wrong is the short exposure at these apertures.
    He hasn't exactly said which of the two he uses(f8 or f11) and he mentions a few seconds rather than an actual number but let's say his few seconds is 3 and his min aperture he currently uses is f11 then f22 is only 12 secs. Still quite short for any dodging and burning. On that basis f32 is really the first f stop that is comfortable for relaxed dodging and burning. Unfortunately even f22 gives concerns over diffusion and presumably f32 is well over the last safe aperture to avoid diffusion so as a solution is dismissed.

    So sticking to the problem mentioned in henpe's post it looks like he needs to stop at f16 and use "work-arounds" such as extra neutral colour filtration or add ND into the filter drawer, doesn't he?

    pentaxuser
     
  21. OP
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    henpe

    henpe Subscriber

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    Sorry for my silence.

    Pentaxuser is right on track. At f/11 I get about 4sec, which is way too short for me to do dodging/burning. I prefer to be in the range 20-30 sec, which would require about f/32 and above. I do not like these large f-numbers since I am afraid to loose sharpness due to diffraction. I think my work-around solution will be to go from a 250W- bulb to 200W, and then try to add some kind of nd-filter (nd-filter for lightning applications was a good recommendation) in the light-path and above the mixing chamber; hopefully this will solve my problems.
     
  22. OP
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    henpe

    henpe Subscriber

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    It won't solve my problem, but I have been thinking about the efficiency of the bulb. I understand the CLS450-head/Laborator1200 is from the 70ties. Does anyone know if halogen bulb technology has improved significantly since then in terms of luminance output efficiency?
     
  23. Lachlan Young

    Lachlan Young Member

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    Before you do this, please try f16 & 30-60cc of CMY. Seriously. You are drastically overthinking a very minor problem.
     
  24. John Koehrer

    John Koehrer Subscriber

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    Here in the US Roscoe is a source for lighting gels. Is/are there Theatrical lighting suppliers somewhere around the continent?
    If you decide to try gels again put them between the mixing box and negative, not above.
     
  25. OP
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    henpe

    henpe Subscriber

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    Note taken :wink:
     
  26. Lachlan Young

    Lachlan Young Member

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    I do those sort of enlargements on a routine basis without trouble using an Ilford MG500 head (2x300w) - it should be easier for you with over a stop less power! Remember that a 3x enlargement allowing for 8lp/mm on paper only needs 24lp/mm on the film (in a lossless system, but the losses are not too drastic, especially not in a relatively small enlargement - and stopping to f16 or even 22 should be fine).

    Good luck :smile:
     
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