thanks all for that responce to cyan, one more question to pete, I have been working with ilford MG IV on LPL color enlarger with the combination of magenta and yellow filters, almost all the time I do split-filtering to get the right amount of grays and rich blacks, I never knew that magenta and yellow are not to be used together, can anybody explain 'ideal' method of working with these color filters on VC papers? Thanks again Shreepad

-- shreepad (middlegray@hotmail.com), November 09, 2000

Answers

Hi Shreepad. Sorry if I confused you with my muddled thinking in the previous thread. I use my own LPL 7700 mainly for colour printing, where things are a bit different, and I prefer to use an old condenser enlarger with a filter draw for VC paper.
Anyway, to try and clarify things:
If you use the magenta and yellow filters together you'll get some component of red in there which, as DJ says, the paper is blind to.
Ilford give two systems for using their MGIVFB paper with dichroic colour heads. One method is to use only the magenta or the yellow filter, and apply an exposure correction factor for each paper grade. The second method is to use the yellow and magenta filters in combination, which keeps the exposure constant throughout the range of grades. In this second method, the red filtration that's produced by mixing yellow and magenta simply acts as a neutral density, as far as the paper is concerned, and automatically corrects the exposure. The contrast of the paper is set by the 'left over' yellow or magenta filtration that doesn't mix to red.
So it's not that you can't mix yellow and magenta, it's just that the effect of the two on the contrast of the paper is to cancel themselves out.
I still don't know whether I'm helping or confusing here. Can I explain it another way?
Multigrade paper has a mixture of blue and green sensitive 'layers', each with different contrast characteristics. The blue sensitive, high contrast part is affected only by the yellow filter (minus blue), and the green sensitve, low contrast part only responds to magenta filtration (minus green). When yellow and magenta are used together, they just have the effect of reducing the total amount of light that the paper is sensitive to.

I suppose the short answer is to just carry on doing what you've found works, and ignore the technicalities.

-- Pete Andrews (p.l.andrews@bham.ac.uk), November 09, 2000.

good explanation Pete.. I even understood that! :)

I've always stuck with the graded filters just cause it's simple :) and the colour head enlarger I was using was hard to read the scale in the dark (even though it was luminous)

-- Nigel Smith (nlandgl@unite.com.au), November 09, 2000.

Thanks a lot pete I got it now. just one more question, as ur working in color printing, Can the filters be used to print color negs on bw paper with some kinda riverse filtration as to get better results? tanks anyway. shreepad

-- shreepad (middlegray@hotmail.com), November 11, 2000.

I've never got wholely satisfactory results from colour negs on B&W paper. VC paper gives reasonable results, but only special panchromatic B&W paper (Kodak panalure for instance) gives the correct tones. You then have to work in the dark, or with the same dim safelighting as colour printing paper.
These days, digital scanning is the best way to get B&W from colour negs or slides.

-- Pete Andrews (p.l.andrews@bham.ac.uk), November 13, 2000.