Various colour enlarging techniques with different materials and processes over the years have used Cyan filtration, however with RA4 you shouldn’t ever require Cyan, unless as described by Bob D569.
That said, Cyan is actually controlled in colour negative printing by density. If you have a print that is too dark, then you will mostly find it is a bit red, usually one or two units too much.
By pulling the exposure by around ¼ of a stop in time, or by changing the aperture by about a ¼ of a stop to reduce the exposure, you will accomplish two things. You will have made the print lighter, and the red should disappear. Effectively adding Cyan!
Except you may not get true ND; there may be a filter cast introduced.
Originally Posted by Bob-D659
The idea works well if you are using a negative translator, or happen to have a Kodak set-up photometer, which will automatically filter out any bias in the filter settings. By bias I mean that if you had set the filter dials to 45Y 50M, you might find, if you compared the readings on your translator with the filters in and out of the beam, that you actually had, say, 41Y 53M. The problem is that filters age, they fade and chip, and get dirty and dusty, and there can also be mechanical problems with the cams and tracks used to position them in the enlarger head.
In one operation I worked at in the past I made internegatives, as well as Ektachrome dupes and Type C prints on the same enlarger. All the darkrooms in this operation had really nice Minolta-Zyco translators, and there wasn't a single enlarger head, out of about 15 darkrooms, which tracked with 100% linearity. One enlarger I had in my darkroom was fitted with four filters; cyan, magenta, yellow and neutral. When making small density adjustments using that particular enlarger, dialing the density wheel would cause very small (1-2 CC) colour shifts, so it wasn't 100% neutral.
BTW, cyan and yellow filtration are used for Ektachrome printing and when making duplicate transparancies on Ektachrome and Fujichrome duplicating stocks. I have also used the cyan filters when printing a negative exposed under florescent lighting; under those circumstances, you end up removing all of your magenta filtration out and adding a not-inconsiderable ammount of cyan filtration.
But Bob-D659 is correct; for the most part, don't touch that dial!!
You may need to use cyan filters for Ilfochrome printing due to the fact that it is daylight balanced. You use M+Y filters for negative printing because it is tungsten balance. (this is an oversimplification)
Do not use all 3 filters for reducing light intensity because it can introduce a color bias. Use a true neutral density filter for that purpose, or stop down the lens and reduce the exposure time.
In rare instances lately (2+years or so) there have been reports of Fuji CA paper requiring cyan filtration. My investigations so far say that there were either problems with the paper, or the process. CAII paper, introduced in 2006 requires a new developer and development time.
Does this mean that CAII will not work correctly with standard Kodak RA developer and bleach-fix?
Originally Posted by Photo Engineer
According to a presentation by the Fuji engineers at the ICPS conference in May of 2006, the answer is "NO".
Originally Posted by Tom Kershaw
Cyan is needed as neutral density, for R-prints and possibly Ciba printing, in the rare instance you need more red and or when yellow and or mag is at zero.
Oops R prints do use C -- my mistake.
Cyan used to create a neutral density will cause a varying color bias as you adjust filtration due to the impurity in the filter coloration when compared to a true neutral. As an example, cyan adds a variable yellow component as you change the cyan filter level. This would require a reduction in yellow as cyan goes up, otherwise the beam begins to turn yellow instead of remaining neutral.
Cyan filtration should be confined to only reversal printing unless there is a gross error in the negative film processing or exposure conditions, or the film is bad with severe fogging. These are rare conditions such that if you meet with them, you have a problem with the system somewhere.
Average "GOOD" use should require M+C or Y+C for Ilfochrome and M+Y for all color negatives.
In over 50 years of color work, I have never had to do otherwise, nor have I known of anyone else who has unless there is a problem as I describe.
I have printed a lot of Cibachrome and you usually use Cyan and yellow filtraton. When printing ra4 you do not use cyan.
If you run out of Y or M or Both, you would make things worse if you use Cyan. You will actually need negative cyan, which is not possible. The solution is to use an aditional filter Y, M or Red (Y+M).
I have a Durst Color head which had an additional + 30 Red (Y+M) if you ever had a case where you run out of the regular Y or M
As other have previously said, you should never use the three filters together.
Cyan is commonly used in positive to positive printing (cibachrome/ilfochrome).
To clarify my previous post, If you run out of the maximum Y+M filtration you will need an additional Red fiter. In the case zero Y or M is not enough, then you will need cyan. Anyway one of the filters should be zero.
What about printing from an unmasked color negative film like Rollei Digibase CN 200? Will you need Cyan filtration in some cases?