Thanks Ben for reaching out with questions. The 40cc filter if memory serves is used to neutralize the w54 Aristo cold light head so that the manufacturers "Subtractive" filter paks can be used to control various grades of contrast with MC papers. All MC papers are designed to react to Green and Blue light, green being used to effect soft contrast while the Blue is used to effect the higher contrast layer of the paper. It's important to note, if you are able to use the Green and Blue gels then printing times will be greatly reduced as this is an "addictive" type of color filtration, essentially the exact opposite of manufacturers contrast filter paks, there are reasons they use the numbered system which is not necessary to go into here. Here is a video from my YouTube channel that describes how MC papers work and also illustrates the various different light sources which can be used to use MC papers.
https://www.youtube.com/watch?v=uRlq8CwVvws
Unfortunately, at least on my older Mac computer the color rendering of the Roscoe Blue # 68 and Green # 389 is not accurate on my screen. The Rosco gels are very inexpensive and are used in the Theatre industry to colorize stage lighting. So long as you are able to use the filter "above" the negative to alter the color of the light source there will be no degrading of the enlarged image.
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