filters and fstops : LUSENET : B&W Photo - Printing & Finishing : One Thread

I'm still finding my way around this Focomat/Wallner enlarging combination. From what I have read on the various posts I can dispense with the Kodak Polycontrast filters because the yellow and magenta filters in the colour head will do the same work, but with the benefit of infinite control (not only that, but I haven't the faintest idea how to attach the polycontrast filters to the the enlarger anyway). I just don't know where to start - should I have all the filters dialed in to some standard number and always start from there? Also, how does f-stop affect contrast? (are these two very separate issues?) Thanks, as always. SMM

-- Shelagh Mathers (, January 26, 2001


I can send you the dial in numbers for the color head if you want. I have them at home in PDF printable format. Cheers

-- Scott Walton (, January 26, 2001.


The f-stop setting on your enlarging lens only affects exposure; it does not affect contrast. To control contrast with VC paper, you should start with 0 filtration. As you increase magenta filtration, the contrast of the paper will increase. If you increase yellow filtration the contrast will be lower. Papers do not react the same to varying levels of filtration. If you know the correct exposure with one filter setting and change filtration the exposure may also change. The only way to determine the effects is to test your setup. An excellent book on the subject is The Variable Contrast Printing Manual by Steve Anchell.


-- Pete Caluori (, January 26, 2001.

The instruction leaflet that comes with the VC printing paper should give you the yellow and magenta filter settings for the various contrast grades. Grade 2 is considered normal.

-- Pete Andrews (, January 26, 2001.

With the filters set to 0 you will have about #2 contrast. For less contrast on a print, increase the yellow, for more contrast increase the magenta. The only reason to use both together is to normalise the exposure time. I don't bother. I make a correction based on the filter factor of the filtration, or if small amounts, I don't bother.

Also equal settings of all three colors is neutral density, which you can use to increase printing times for dodging or burning.

-- Terry Carraway (, January 28, 2001.

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