Adding An Extra Magenta Filter

Discussion in 'Darkroom Equipment' started by ragnar58, Mar 18, 2013.

  1. ragnar58

    ragnar58 Member

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    Hello to all,
    Does anyone have comments or suggestions about adding an extra magenta dichronic filter to a Super Chromega housing?
    I can't get really high contrast with the current magenta alone and would like to replace the cyan filter with a magenta filter. I'm assuming that the values will add when both filters are used. Using a dial is easier than inserting filters under the lens. I know that I'll lose some flexibility without the cyan but this seemed to be the best solution.
    Thanks
     
  2. boswald

    boswald Member

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    If your head is a D or DII you can fit a 6x6 filter in the bottom of the 4x5 mixing box. The lips under the diffuser are spaced perfectly. You can slide the filter in with the mixing box in place, and pull it out partway to remove. Not as elegant as dialing but cheap to try.
     
  3. ann

    ann Subscriber

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    for printing black and white you don't use cyan, so it shouldn't be a big loss. Color , a different story,
     
  4. Bob Carnie

    Bob Carnie Subscriber

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    no the values will not add up.

    If you get 200 Magenta with your enlarger one filter is it , adding extra filter will not get you 400 magenta and extra contrast.
    You will just increase your exposure time, and quite dramatically as every 30 filter increase in the Magenta will reguire you an extra stop of exposure on your print.
    so I would not even consider this.

    Bob

     
  5. PKM-25

    PKM-25 Member

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    So is 200 magenta equal to a grade 5 MG filter or....? I have never really compared them on my 45S head and seem to get plenty of contrast from the color head, but now I am curious...
     
  6. MattKing

    MattKing Subscriber

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    Check to see if the magenta dichroic filter needs cleaning.

    Also check that the cyan filter isn't stuck in the light path.
     
  7. Bob Carnie

    Bob Carnie Subscriber

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    Its the most contrast a diffusion enlarger can deliver without purchasing specific filters which is beyond the $$$scope of most darkroom workers.
    I consider it around a 4 1/2 to 5 for my workflow and do get a great DMax.

     
  8. Bob Carnie

    Bob Carnie Subscriber

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    Very good point.

     
  9. Gerald C Koch

    Gerald C Koch Member

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    The fact remains that you cannot get any higher grade than the "hard" emulsion layer is capable of delivering. So past this point no increase in magenta filtration will have any effect other than making exposure times longer.
     
  10. Doremus Scudder

    Doremus Scudder Member

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    ... also, adding another filter of the same exact color will not gain you anything. The strongest filter (assuming one is stronger than the other) will prevail and the other will do exactly nothing, except to increase your exposure time a little (not as much as Bob suggests above though, since you are filtering already filtered light and the transmission will be close to 100% minus the neutral density characteristics of the filter).

    If you need more contrast for a particular negative, try the following:

    Try a different paper (I've heard that Fomabrom Variant 111 is more contrasty than other VC papers)
    Use the MG grade 5 filter (it may be more contrasty than the magenta in your color head by a bit)
    Use a stronger/more contrasty print developer
    Bleach back the whites after printing a bit darker


    If this is a recurrent problem then:

    Develop more to start with
    Check your magenta filter to see if it has faded; replacing it with a new/good used filter may help

    Best,

    Doremus
     
  11. MattKing

    MattKing Subscriber

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    It is rare that I would consider disagreeing with Doremus, but ...

    If the filter is a dichroic filter, it is an interference filter that won't fade.

    They do, however, become less effective if they become dirty.
     
  12. Gerald C Koch

    Gerald C Koch Member

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    While dirt on a filter might cut down on the amount of light there should be no change in its spectral response.
     
  13. RPC

    RPC Member

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    The cyan filter is not used when printing from color negatives, slides may require it.
     
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  15. ic-racer

    ic-racer Member

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    You have a problem that will not be solved by additional magenta filtration.

    Start from the beginning, how are you determining your printing contrast?
     
  16. Bill Burk

    Bill Burk Subscriber

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    Dug around your earlier posts where you say the maximum for a Chromega is 170 units, and you do split-grade printing.

    So burying an additional Magenta inside the housing would become a chore. I'd put a 30-50 Magenta filter in front of the lens so you could go up past 200 if you wanted to.
     
  17. boswald

    boswald Member

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    There is a basic difference in the way dichroic heads and filter drawers use their filters. A filter in a drawer filters all of the light while a dichro head(subtractive w/moving filters) filters some of the light till you get to the maximum position, leaving some of the light unfiltered most of the time.
    A second magenta would in fact reduce the light for the high contrast layer, rebalancing the output toward the low. You would need to use a separate filter to get rid of the light that goes past the edge of the moving filter. Not much- a 40m in the drawer would let you get all the contrast available when added to a fully magenta blocked aperture.
     
  18. MartinP

    MartinP Member

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    Ilford under-lens filter kit, with white-light from the enlarger?? Works for me anyway, and I made holders from foamboard that allow easy lens changes (the holder that comes with the set, mounts on the lens thread).
     
  19. cowanw

    cowanw Member

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    Not to make things more confusing, but I have the same enlarger and head, and I find the Dichroic filters can be a bit short on maximum contrast. My serrendipitous solution was to get an old set of dupont or kodak under the lens filters, with bakelite screw on the lens holder. The number 5 there gives a contrastier result.
    On the assumption your dichroic filtes act as perfect filters, doubling up on the same filter will only let the same image developing wavelengths pass twice, but will make it harder for your eyes to see the image on the easil.
     
  20. Bob Carnie

    Bob Carnie Subscriber

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    filtering filtered light.. you are right , I was thinking of the relationship on colour paper when you add magenta..
     
  21. Bob Carnie

    Bob Carnie Subscriber

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    If you are printing crossed processed colour negs then you will indeed need to use the cyan filter.
    As well introducing the cyan filter will give you nuetral density which may be needed if your exposure time is too fast with a good apeture.

     
  22. DREW WILEY

    DREW WILEY Member

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    At 200M, you're already way past what the paper will handle in terms of contrast, unless your filter element has faded or scaled off its coating (sometimes but rarely happens). You can also just place a hard blue filter like a 47 under the lens, if it's of good optical quality, and nothing but the blue light will get thru.
     
  23. cliveh

    cliveh Subscriber

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    I would suggest your problem lies with your original exposure of the negative and its development.
     
  24. ragnar58

    ragnar58 Member

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    Thanks to all for the helpful comments. I did not expect this many responses to what I had seen as a simple question. The question was not specific to a particular image but was a general question for a future option. I’m currently pondering the benefits/burdens of unsharp masking and filtration seemed to be a key factor. I was considering a few issues with the replacement of the cyan filter with a magenta one.

    1. Several paper manufacturers’ datasheets show the Omega system (based on Kodak cc units) will not achieve a G5 contrast without additional filtration. Wouldn’t adding magenta into the light path be equivalent to adjusting cc filter packs in the old days of color printing? Of course, the amount added to reach maximum effective magenta light may only be 50 units from the second filter.

    2. The Omega system efficiency is reduced with the small amount of light leakage around the filters. In addition, no filter is 100% effective, so the system never achieves the potential maximum magenta light. I figured that the extra filter is needed to get it closer to the maximum.

    3. As I have measured it, with MGIV I get around G4.25 in Dektol 1:2, which would be sufficient 90% of the time. I know that I can use different dilutions, longer developer times, or specialized developers but I thought the additional magenta filter would be the easiest to incorporate.
    If the unsharp masking technique becomes a routine practice for me, this seemed to be the best long-term solution. Nothing else would change, only the added option to crank-it-up-to-11 when needed.

    I’ve had the head completely apart for a thorough cleaning; so replacing the filter isn’t difficult. The current filters are intact, clean, and the mechanisms work smoothly. With a B&H cost of $68.99 with shipping for a new filter, I don’t plan to move quickly on this project. Maybe I can find a used color head to cannibalize.
     
  25. Nicholas Lindan

    Nicholas Lindan Advertiser

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    The reason you can not get to maximum contrast with a color head is because the magenta of the color head is different than the magenta of a VC filter. Just the same as there is not one color 'green' there is not one color 'magenta'.

    A color head's spectrum is matched to the sensitizing dyes used in color paper, and these are different from sensitizing dyes used in VC paper. The cutoff of color and VC filters is different. For maximum contrast a VC filter can not pass even the slightest hint of greenish-blue light.

    You can add a zillion dichroic filters and it won't affect the maximum contrast because it won't change the filter's cutoff.

    To get more contrast you need to place a real #5 VC filter in the light path.
     
  26. Doremus Scudder

    Doremus Scudder Member

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    Matt,

    Please continue to disagree with and correct me whenever you see fit! Thanks for the heads up. I have done a bit of research on dichroic filters and the technology behind them and now know that they will not fade since the color of the filter is inherent in the interference characteristics of the coatings.

    If you hadn't posted, I would not have read the articles on dichroism and thin-film interference.

    Thanks,


    Amen to this.

    Best,


    Doremus


    www.DoremusScudder.com