Using Cyan when colour printing

Discussion in 'Film and Processing' started by curtis_lowe, Jun 3, 2009.

  1. I know cyan is not normally required when colour printing as you can make the colour changes by using yellow and magenta filtration only. So I leave cyan at zero and I use the other two dials to correct colours, but if my yellow dial has reached its maximum and I still have a yellow cast, I can't move the yellow dial up any more so I now would have to reduce magenta and cyan. The problem is that my cyan would already be at zero so I'm a bit confused. It has not happened to me yet but I'm just curious.
     
  2. You could just add a CC50Y filter on top of the neg.
     
  3. Color paper consists of three emulsion layers. Each fabricated to be sensitive to just one primary color. The primaries are red – green – blue. Each of the three filters partially block just one color of the three primary colors while transmitting two of the primaries. The values are cryptic (logarithmic notation) but they measure how much energy is blocked. 5 = 1/6 stop – 10 = 1/3 stop – 20 = 2/3 stop – 30 = 1 stop – 60 = 2 stops – 90 = 3 stops – 120 = 4 stops.
    Cyan filter blocks red and passes green and blue.
    Magenta filter blocks green and passes red and blue.
    Yellow filter blocks blue and passes red and green.
    The yellow filter performs with nearly 100% accuracy
    The magenta filter operates at 70% efficiency because as it blocks green it also undesirably blocks some red and some blue.
    The cyan filter is poor (we have never been able to make a good one. It blocks red but unwanted absorption of green and blue takes its toll so the system is designed to avoid its use.
    The idea of the filters is to adjust the red – green – blue energies received by the paper during exposure so that each of the three paper emulsions receives an exposure that is spot on. If one or more is incorrectly exposed the color balance of the final print will be in error.
    Normal conditions: With the lens aperture wide open and the filters all set to zero, too much of all three colors will be delivered to the paper. As you close down the aperture, all three energies are reduced in unison. As you continue to stop down the lens the light energy to be received by just one of the emulsion layers will become on. The system is designed so that the red energy will be the one that is spot on, no need to attenuate red with the cyan filter. Thus the cyan filter is almost never used (good news, it’s a trouble maker anyway).
    OK, the red energy is correct, how about the green and blue? The system is designed so theses will be in excess. Now we use the magenta and the yellow to attenuate green blue. In other words, the aperture established the red exposure, the magenta filters sets up the green exposure and the yellow filter adjusts blue exposure.
    What happens if the energies are wrong?
    Too much blue light – print goes yellow
    Too much green light – print goes magenta
    Too much red light – print goes cyan
    Too little blue light – print goes blue
    Too little green light – print goes green
    Too little red light – print goes red.
    Your yellow filter is set to maximum. Yet, too much blue light is being delivered during exposure.
    Countermeasure – Add additional yellow filter. I suggest you purchase or borrow some yellow. Procure some cut sheet filters – CP (color printing) are not optically flat and must be placed in the lamp house. CC (color filters) are high quality and can be anywhere including the image forming rays. I suggest two 20 yellow CC’s. 50mm square. Remove the lens and insert one 20 yellow CC and replace lens. The idea is to add yellow at the lens because at this location a inexpensive small filter will be OK and you can stack two or more CC’s.
    Your situation is abnormal. Perhaps the film is abnormal due to one or more; processing error, exposing conditions error, film age, heat or fume from volatile chemicals. Likely you will not be satisfied when all is said and done.
    Adding cyan filter will not solve this problem – cyan is a red blocker. You need a blue blocker, only yellow filters will do the trick.
     
  4. is it possible that the yellow filters in your enlarger are old and faded?
     
  5. It hasn't happened yet but I was just curious as cyan would already be at zero and I could not reduce it and magenta to decrease the yellow in the print.
     
  6. I had a roll of Reala once that needed the cyan filter. If I recall correctly it was 50M and 10C.
     

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