So, what is that Cyan wheel for?

So, everyone use Magenta and Yellow for VC papers and if I understand right use only these two wheels for colour too? So, what is the Cyan wheel for?

/matti

Making chrome prints or balancing for making 'daylight' type exposures on-easel.

PE

Thanks PE. Would it change contrast on a VC paper, or could it be used as an nd-filter?
/matti

If you have a 10 C a 10 M and a 10 Y you have a 10 ND, approximately. It is higher due to unwanted absorption.

PE

Since cyan filtration (on orthochromatic paper) only passes red to some degree, there is no visible effect as ND. Y+M filtration suffice as being used for ND.

M.

it is used for color printing along with the others

"Back in the day" SOP for me was to use some C filtration along with Y+M for ND with color materials. I tried to use moderate apertures since enlarging lenses tended to be sharper a couple stops down and IME could degrade the image at the smallest stops. The added ND helped regulate which stop (and overall exposure time) I could use. Plus, it seemed easier and more convenient to remove/add a point or two of C instead of both Y+M. Having the ND originally dialed in gave me the flexibility to do that.

Joe

In color printing, you may need a cyan filter for an older C-22 type neg, which will have a very different base color than a C-41 neg. Or, you may need it to print a color neg shot under fluorescent light with no filtration. Dean

Dean;

I would have to say that the only C22 negative that does not print with red filtration is the short lived CU (Universal Kodacolor). The CU film is half way between daylight and tungsten in balance. In fact, the color of the base has nothing to do with the real balance, it is the speeds between the 3 layers that are balanced to get the correct color.

PE

Photo engineer: thanks for the clarification. I'm falling back on my experience as a custom color printer (long ago) and remember identifying the C22 negs by sight. They were never compatible with the RA-4 papers.
I caught the very tail end of Ektaprint C. 1st dev; color dev; bleach; fix; hardener and stabilizer. About 22 minutes dry to dry, depending on the processor. But it was real fibre base paper. Dean

Photo engineer: just found the RA4 thread under darkroom. Very interesting. Goes way beyond my meager knowledge of the subject. Dean

I do RA4 printing and it doesn't require cyan filtration but I do use it as ND filter. With the Beseler computerized color head this can be done very precise. That is why I like this head better than the simpler 45S head although it's more prone to problem with the circuit board.

FWIW, I've been reprinting a bunch of old C-22 negatives (family photos) lately, and most of them require very little filtration in an absolute sense -- they're all close (but not quite identical) to equal C/M/Y filtration (or actually R/G/B color levels, since I'm using a Philips PCS150 additive light source). Many of them require slightly more cyan filtration (less red light) than magenta or yellow filtration (green or blue light) -- on the order of 5-10cc units.

In an earlier thread, PE mentioned the "universal" film he's mentioned here, but I've now printed negatives ranging from 1964 to about 1973, and they're all the same, so I now doubt if that explains what I'm seeing. Perhaps my negatives have faded, or maybe it's a quirk of my enlarger or of the paper I'm using (Agfa Signum II for most of the prints so far), but modern negatives always take less cyan filtration (more red light) unless they're shot under unusual lighting conditions. I've gotten fine color, so if the negatives have faded it's been in a way or to an extent that's not been obvious in the final print.

On a more general note, I almost always use cyan filtration (reduced red light output), in conjunction with equivalent changes to my magenta/green and yellow/blue channels, as ND filtration. Modern color papers are fast enough that I simply can't get exposure times that are long enough if I set the cyan/red dial at "0" (no filtration/maximum brightness). Even stopping down my lens all the way, exposure times would be shorter than 5s (the minimum on my equipment) for small prints -- certainly for the postcard-sized reprints I'm doing in my old-negatives project, and often even for 8x10 prints.

When making B&W prints, I turn off my enlarger's red light (equivalent to maximum cyan filtration) to extend bulb life, since the red light doesn't have any noticeable effect on my B&W prints but using it burns one of my enlarger's three bulbs needlessly. I don't see any reason to crank up the cyan filtration all the way on a conventional subtractive enlarger, though; it wouldn't help extend bulb life or do anything else useful, AFAIK. Using it for ND filtration might be necessary in some cases, though, and of course there's the possibility it'd be needed for oddball negatives or when printing slides.

Just for general information, the cyan layer of Kodak color papers is about the eqivalent to that of Ilford MGIV or any other B&W paper, and is about equivalent to ISO 25 or so. On the same scale, the magenta layer is about ISO 100 and the yellow layer is about ISO 200. This arrangement is so that it compensates for the tungsten balance of most enlargers and it also balances the blue sensitivity of the green and red layers with the filtration.

The reult is that you need about 50 Red to print with a 'normal' enlarger.

All of my negatives from about 1950 forward to today print with about a 70 red and have done so on 5 enlargers that I have used over those years. The exception is the CU Kodacolor.

It is easier to make a paper with matched speeds, but at the sacrifice of using 3 filter wheels complicating exposure, and at the expense of having more orange yellows due to less color separation between layers. Greens will also tend to shift as will cyans with this speed.

To achieve this speed separation, the yellow layer is a 2.0 micron grain while the cyan and magenta are 0.2 micron (approximate edge length) and this is much more difficult so some manufacturers take the easy way out. If you have matched speeds in all layers, you can use the same emulsion in all layers and you must put the yellow layer on top. This decreases dye stability as well, as yellow is particularly sensitive to UV.

Kodak has gone for color purity and some safelight capability. Along with this is easier printing on most enlargers and better dye stability.

PE