hi I have been printiing on Ilford MgIV with LPL color enlarger I was flattered to see the amount fo contrast controll you get with MAGENTA and YELLOW filter combinations. Just one question, Does anybody know what effect does the CYAN filter do on Multigrade? If the paper is not responsive to the color can it be just to lengthen the exposure times?

please help

-- shreepad (middlegray@hotmail.com), November 06, 2000

Answers

Cyan has no effect.

-- John Hicks (jbh@magicnet.net), November 07, 2000.

The Cyan wheel will neutralise the effect of equal quantities of Yellow and Magenta, effectively adding in a neutral density, and as you guessed, lengthening the exposure. The values are true density x 100, so 30 units of each = 0.3D, which halves the light intensity.

-- Pete Andrews (p.l.andrews@bham.ac.uk), November 07, 2000.

Actually, isn't the paper blind to the red light that cyan blocks? So regardless of whether you add or subtract cyan, it should have absolutely no effect on your printing (since you are adding or subtracting colour that the paper is blind to anyway). Cheers, DJ.

-- N Dhananjay (ndhanu@umich.edu), November 07, 2000.

That's true DJ. You never use both the yellow and magenta together with VC paper. What was I thinking!

-- Pete Andrews (p.l.andrews@bham.ac.uk), November 08, 2000.

I dont know about never Pete I have added equal amounts of yellow and magenta to lengthen exposure times.-J

-- josh (devil_music@usa.net), November 12, 2000.

Try replacing the cyan filter with something opaque, making it a continuously variable ND filter. By making a series of test prints with a step wedge at different levels of yellow (only), magenta (only) and ND (only) filtration, you can easily figure out how much ND to dial up with different levels of yellow and magenta to maintain constant exposure while changing contrast.

-- Chris Patti (cmpatti@aol.com), November 13, 2000.

Chris,

Color enlarger dichroic filters don't work like that. You can't just replace the cyan with a ND filter.

-- Terry Carraway (TCarraway@compuserve.com), November 14, 2000.

Terry,

I've done it and it works. By the way, I didn't replace the cyan filter with an ND filter but with a piece of opaque material (cut out from an aluminum can), although I don't see why an ND filter wouldn't work if you could fashion one that would fit. The dichrotic filter works by moving a colored filter further and further into the path of the white light entering the mixing chamber. As the modified "cyan" filtration is dialed up, the opaque "filter" blocks an increasing amount of light, functioning as an ND filter. When the magenta or yellow filters are dialed up, the "cyan" ND filter is dialied down and vice-versa, allowing constant exposure with different levels of magenta and cyan filtration. Obviously, one unit of the "cyan" (now opaque)blocks far more light than a unit of the transparent magenta or yellow filters, so you have to calibrate. This modification technique was described within the last year in one of the photo mags but I can't remember which one or the author (maybe Gordon Hutchings or Howard Bond). The article provided illustrations showing how to do the modification. The article also describes a calibration technique which is unnecessarily complicated and indirect. It would be better and easier to use a variation of Paul Butzi's technique, which is described at http://www.asymptote.com/butzi/articles/vcce.htm.

-- Chris Patti (cmpatti@aol.com), November 14, 2000.