Dichroic head + under lens filters versus Dichroic color head?

Discussion in 'Enlarging' started by Cymen, Apr 17, 2009.

  1. Cymen

    Cymen Member

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    What is the difference between using a dichroic head with under the lens filters versus a dichroic color head with the built-in filters? I assumed dichroic head meant color dichroic head and thus brought an enlarger that is so named yet came with an empty box where the color filters are in the color head version.

    Am I missing only a slight convenience by not having built-in color filters? Or is there more to it? I have seen this discussed in terms of condenser or cold head with under lens filters versus diffusion with built-in filters but not the case where both heads have diffusion light sources.
     
  2. Bob-D659

    Bob-D659 Member

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    Ummmm.. A dichroic head has built in filters by definition. Could be someone gutted the unit you have. Now are you talking about a colour dichroic head or one for multigrade black and white. They are different, as under the lens filters don't work with C41 type colour negative printing, only black and white.
     
  3. Cymen

    Cymen Member

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    No, I'm talking about the Omega/Saunders/LPL 4500-II. It comes with the option of a "B&W module" which is an empty box, a color module or a VCCE module. These modules slide in between the light source and the diffusion chamber. The B&W module really is an empty box. The front of the head (not the module) says "Super Dichroic". It doesn't help that the B&W module is the color module without the guts but with the moldings where the 3 color adjustment displays are in the color head. This is it on B&H:

    http://www.bhphotovideo.com/bnh/controller/home?O=&sku=45697&is=REG&A=details&Q=

    The description is wrong though (it discusses the two other modules).

    But to return to the question: Is there much of a difference between using the same diffused light source with dichroic filtration versus under the lens filters?
     
  4. Nick Zentena

    Nick Zentena Member

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    If you mean the end results it shouldn't be. Obviously if you're printing colour it'll be more of a hassle shuffling filters then turning the dial. For B&W less so of an issue.
     
  5. RH Designs

    RH Designs Advertiser Advertiser

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    If the actual filtration is equivalent in both cases, then no, there isn't.
     
  6. bdial

    bdial Subscriber

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    With the Saunders LPL color head you can't get to 0 or 5 contrast levels, at least with Ilford paper. At least when I tested this, max yellow was about the same as a 1/2 Multigrade filter, and at max magenta it was about the same as a print made with a 4 MG filter.
    So, I've hung on to my MG filters for just this reason, but I've never had a reason to actually use them for doing anything other than the original test/comparison prints.

    The convenience and the ability to tweak even in-between half grades, makes the color head really nice however.

    If you are contemplating buying a dichroic module, I'd recommend the VCCE module, if you're planning to do only B&W.
    I haven't tested the extremes on the one that's available to me, but it's easer to use, since you can just dial in the contrast level without referring to a chart to use Y & M on a color head.
     
  7. markbau

    markbau Member

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    Putting a filter in the light path between the lens and the paper opens up the possibility of degrading image quality unless the filters are perfectly clean and free of any scratches. Personally I would never put a filter under the lens.

    Mark
     
  8. RH Designs

    RH Designs Advertiser Advertiser

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    The Ilford filters are so thin and so far out of the plane of focus that their effect is invisible. I have never noticed any image degradation when using under-lens filters. Scratches might have an effect but a few specks of dust certainly don't.
     
  9. srs5694

    srs5694 Member

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    There was a recent thread here on APUG (sorry, I don't have a URL) about old under-lens filters degrading and causing flare, among other problems. I've no experience with this myself, though.
     
  10. Neal

    Neal Subscriber

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    Dear Cymen,

    Keep a set of under the lens filters around for the extreme cases, but the convenience of the built in filters is wonderful. Besides, you can free yourself from the concept of paper grades. If you want more or less contrast you just dial it in.

    Neal Wydra
     
  11. RalphLambrecht

    RalphLambrecht Subscriber

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    Correct! We tested this a few times. Clean under-the-lens filters cause no degradation of image quality.
     
  12. RalphLambrecht

    RalphLambrecht Subscriber

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    Yes, but the ability of fine-tuning is the biggest difference between under-the-lens filters and a dichroic head in my opinion.

    1. I don't want to miss the fine-tuning opportunities of a dichroic head.
    2. I don't want to miss the convenience of under-the-lens filters.

    I think, I've got a problem. ... No, '1' is more important than '2'.
     
  13. RalphLambrecht

    RalphLambrecht Subscriber

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    Nick

    Not if you have to switch contrast within a print. A little '5' to the sky, oh ... the rocks could do with a '0' burn-in, leave the rest at '2'.
    That's all a pain with a dichroic head and easy to do with under-the-lens filters. Also, split-grade printing is much easier with them too..
     
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  15. RalphLambrecht

    RalphLambrecht Subscriber

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    Why are you interested in the contrast extremes?

    The negatives, I had, which needed contrast extremes, were not worth the printing time. Trash! (Well, that's where most of my negatives and prints are anyway.

    Also, dichroic heads can easily do ISO-grades 0-5 on most papers. What they can't do is match the contrast achievable with filter numbers 0-5. The two are not the same (not even filter numbers among filter manufacturers are the same, not even close), and ISO-grades 0-5 are just fine. For the few prints that deserve the time to print at contrast extremes, keep a set of under-the-lens filters around, just in case.
     
  16. bdial

    bdial Subscriber

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    I'm not interested in printing at the extremes, I agree that negs that far out aren't worth it.
     
  17. RalphLambrecht

    RalphLambrecht Subscriber

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    You are right. That's my experience too.

    There are exceptions of course. For example, the image attached was printed at grade 5 for a reason.
     

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  18. RH Designs

    RH Designs Advertiser Advertiser

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    If you combine the two systems, I guess you can use the dichroics to "tweak" the contrast between filter grades?
     
  19. Ken N

    Ken N Member

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    When split-grade printing, I use 00 and 5 filtration. I can't get grade 5 with the dichroic head. Also, another reason why I use the under-the lens filters for split-grade printing is that I can quickly change between the two exposures in split-grade without bumping the enlarger itself. The time savings is substantial.
     
  20. RalphLambrecht

    RalphLambrecht Subscriber

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    I agree, that's my experience too. Turning the dials on a dichroic head back and forth is a pain. Under-the-lens filters are much easier for split-grade printing.
     
  21. RalphLambrecht

    RalphLambrecht Subscriber

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    Richard

    Combining the two filtration systems is too complex for me. If tweaking contrast is the issue, I'll stick to dichroic heads. If speed and simplicity is the issue, or if I need the flexibility to quickly change grades, I'll prefer to use the under-lens-filters. Combining the two is not simple.
     
  22. Cymen

    Cymen Member

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    Based on these posts, I'm going to try to use under-the-lens filters instead of putting priority on finding a color head. My enlarger does not have provisions for filters so there is no filter drawer or anything else of that type. However, there is an arm next to the lens with a holder that flips into the light path. That holder has a red filter in it which is designed to be removable. It would be possible to place a filter on top of that surface.

    Is that the recommended approach? Or should I search for something more secure. I see the rectangular trays that might be adapted to go onto the same arm as the red filter and the Ilford filter holder that attaches to the lens. It appears to be hard to get the Ilford holder without buying it as part of a kit that includes the filters. That is not a problem though as I currently have an inexpensive set of 3" x 3" cut gelatin filters so buying the kit is fine by me.

    I would try what I have with the red filter holder to see if it works for me but the project of building a base/work bench for the enlarger is taking longer than expected and I need to mail order almost everything. Thank you for the excellent advice.
     
  23. ic-racer

    ic-racer Member

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    I spent about 9 months searching for 8x10 options for MG printing to avoid having any filter in the light path. I gave up and just went with the 6"x6" Ilford filters under the lens and I can say it is working excellent (and I'm using an Aristo W45). To get the quarter steps, splitting the exposure between two adjacent filters works for me.
     
  24. RalphLambrecht

    RalphLambrecht Subscriber

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    I think, being able to print in 1/4-grade increments is fine enough. I try to print down to 1/8 of a grade with dichroic heads and sometimes wonder if I'm not overdoing it a bit, but as long as I can see the difference, I'll continue to do it. However, some filter/paper combinations have almost a grade between 1/2-'grade' filter numbers. Then, 1/4 increments become a must.
     
  25. cowanw

    cowanw Member

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    Part of the below the lens technique involves constantly moving the filter to avoid projection of any gross defects, in the same way one moves a dodge or burn tool. In theory at least
     
  26. RalphLambrecht

    RalphLambrecht Subscriber

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    Bill

    That is not my understanding. The under-the-lens filters, I'm referring to, are stationary and kept in a filter holder, which is typically clipped onto the lens. What kind are you talking about?