Why magenta and yellow filtration

Marameo · Dec 27, 2017

Hello,

I don't have previous experience in color printing but I wonder why the suggested filter pack for a given paper normally is 50M+60Y or suchlike. Is there much red/orange to offset in the paper?

Also, I am accostumed with curves where I can add density in the shadows and pull it out from the highlights for each channel (RGB). For instance, push yellow density in the 3/4 tones. How does that apply under the enlarger?

The only color correction technique I can think of is about temperature constrast (cold/warm) through masks.

Thanks

dE fENDER · Dec 27, 2017

The simplest answer to your first question is that: these values will give you max quality of image. The more theory on the deep roots of the problem you can find at the book of R. Hunt "The reproduction of the colour". But these params are not always have such values. The colour paper for unmasked negatives, produced in Russia till the beginning of 2000 years had starting values about 200 100 0. Last batches of Ilfochrome while it was fresh (2015) had values about 10 20 0. Some R-3 and other reversal papers - 0 50 20. You can try to find some China Lucky paper, which have red color of emulsion and it's starting values will differ from 50 60 0...to the redder range.

The split contrast control in color analog printing is extremely difficult, but possible.
1. You can try to play with developer temperature, custom developers recipes, different color developing agents, different papers and some methods of chemical correction. Probably it will give you some results, but nothing predictable.
2. As you noted, it can be done by masking. The first thing you need to do is to forget about your CMY color head filtration. You need to get somewhere set of narrow red/green/blue filters for color printing, like these:

You have to expose your image three times with different exposures through these. It still not give you what you want, but you will make a step ahead to your goal. The next stage is to pick up required b/w developer and make required mask or mask set at b/w film for required colors, then repeat process of 3 color exposures. After any one you have to pull out your negative from enlarger, apply a mask for the color and put this sandwich exactly at the same position in enlarger. It will require special frame with pins and there is not too much sense in this process.

Prof_Pixel · Dec 27, 2017

It seems to me I heard the reason the layers are balanced as they are (not requiring the use of cyan filter) is because cyan printing filters are not very stable and fade

RPC · Dec 28, 2017

Marameo said:
I don't have previous experience in color printing but I wonder why the suggested filter pack for a given paper normally is 50M+60Y or suchlike. Is there much red/orange to offset in the paper?

The orange cast of a color negative must be removed when a print is made, and the color response of the color print paper is biased to remove it.

This is easy to do, since the nature of silver halides makes it easy to make the paper highly sensitive to blue, moderately sensitive to green, and have low sensitivity to red, just what is needed to offset the orange cast.

And in order to give some headroom to precisely color balance the print, the layer sensitivities are configured such that yellow and magenta filtration, and only yellow and magenta, would ever be needed to color balance the print, which makes color balancing consistent and less confusing.

If in the design of the paper, cyan filtration was paired with one of the other filters, or the values of yellow and magenta needed were much lower, the sensitivity of the red-sensitive layer would have to be brought up considerably, and the layer would be exposed by blue light as well as red due to silver halide's natural sensitivity to blue. Having the red layer sensitivity low prevents this. The green works similarly, but is less of a problem.

halfaman · Dec 28, 2017

Cyan dial is there in the enlarger, why not use it?

I use always cyan filtration and I don't see any problem with it so far. It is the filter I use less, in the range of 10-20ish points in Durst scale while magenta and yellow are in 70-80ish, but prints behaves consistently with the adjustments.

Marameo · Dec 28, 2017

dE fENDER said:
You have to expose your image three times with different exposures through these. It still not give you what you want, but you will make a step ahead to your goal.

This makes seem darkroom color correction more complex then, say, dot-etching in prepress..

halfaman said:
Cyan dial is there in the enlarger, why not use it?

Btw, subtracting magenta is not equivalent to adding cyan and yellow?

dE fENDER · Dec 28, 2017

Marameo said:
This makes seem darkroom color correction more complex then, say, dot-etching in prepress..

It is. So most people just presume that contrast curves are predetermined by paper manufacturer and you have no control at all.

Marameo said:
Btw, subtracting magenta is not equivalent to adding cyan and yellow?

Not equivalent. You cannot synthesize ideal dye, so any cyan and blue dye will have parasitic magenta transmission. Besides - it is the main cause of using orange mask. It you will not shift far enough from parasitic transmission of the blue dye, you cannot get acceptable image.

RPC · Dec 28, 2017

Using all three filters together creates neutral density which means longer exposures. This may be desirable sometimes but normally would not be.

Bob Carnie · Dec 28, 2017

halfaman said:
Cyan dial is there in the enlarger, why not use it?

I use always cyan filtration and I don't see any problem with it so far. It is the filter I use less, in the range of 10-20ish points in Durst scale while magenta and yellow are in 70-80ish, but prints behaves consistently with the adjustments.

You are adding 10-20ish neutral density when you use three filters... which is ok in circumstances where your apeture and time get out of hand.

bvy · Dec 28, 2017

halfaman said:
Cyan dial is there in the enlarger, why not use it?

I use always cyan filtration and I don't see any problem with it so far. It is the filter I use less, in the range of 10-20ish points in Durst scale while magenta and yellow are in 70-80ish, but prints behaves consistently with the adjustments.

Using it just to use it is adding an unnecessary third variable to the color balancing act. As mentioned, if all three controls are nonzero, then you're just adding neutral density. But maybe you have a practical reason.

I have had to use cyan filtration, but only when printing things like cross-processed negatives. In those case, I dialed magenta down to zero and still had too much green in the print. To deal with that, you start dialing up cyan and yellow in tandem.

Bob Carnie · Dec 28, 2017

bvy said:
Using it just to use it is adding an unnecessary third variable to the color balancing act. As mentioned, if all three controls are nonzero, then you're just adding neutral density. But maybe you have a practical reason.

I have had to use cyan filtration, but only when printing things like cross-processed negatives. In those case, I dialed magenta down to zero and still had too much green in the print. To deal with that, you start dialing up cyan and yellow in tandem.

I agree, the only time I got into the cyan filter with colour printing was with Cross Processed negs.

MattKing · Dec 28, 2017

The cyan dial could come into play with Cibachrome/Ilfochrome use.
The orange mask is a benefit - it helps deal with the imperfect response curves of the materials in both the colour negative and colour paper. It is the combination of those response curves, the mask, and how filters respond to halogen or incandescent light sources that leads to a choice of magenta and yellow filtration.
While it might be possible to totally revamp the system and replace all the materials and techniques with systems that are based totally on additive colour and different response masks, why would you?

DREW WILEY · Dec 28, 2017

These answers are related to color negative printing, in which case the film has an orange mask, and the paper typically a blue overcoat. In color positive printing, like Cibachrome from chromes or slides, the cyan control was frequently used. Since modern colorhead filters are dichroic, none of the three fades. If you use all three at the same time, you create a degree of neutral density. Therefore the lowest setting is nulled out to zero, and the equivalent cc value subtracted from the other two settings.

DREW WILEY · Dec 28, 2017

Matt - additive is purer. With subtractive CMY printing, there is always a bit of white light that gets through, exposing all the paper dye, potentially creating a bit of mud. This was more a problem in the past. Dichroic filters don't fade per se, but can over time spall off bits of coating due to cumulative overheating, allowing even more unfiltered light through. Both filters and papers have improved. But additive RGB printing assumes very crisp narrow-band filtration in which none of the other two respective colors passes through. But a good additive colorhead is more difficult to design, and requires stronger illumination due to greater filter density. It sure made a difference for me, in terms of visual hue purity. But given a late high-end Durst colorhead and current color neg films and papers, I doubt the fuss would be worth it. Sequential additive RGB printing (using three different exposures) is even more complicated.

Marameo · Dec 28, 2017

So in terms of color correction, color printing is similar to use only the "temp" (blue/yellow) and "tint" (green/magenta) sliders locally or on the whole frame in a raw converter. I wonder how they made it in cinematography when there was no digital intermediate.

halfaman · Dec 28, 2017

bvy said:
Using it just to use it is adding an unnecessary third variable to the color balancing act. As mentioned, if all three controls are nonzero, then you're just adding neutral density. But maybe you have a practical reason.

The main advantage for me is clarity. I use three dials for three different corrections, not two dials for three different corrections. The possible "neutral density" effect is not a problem as my exposure times are rather short (around 6-10 seconds at f/13 in 8x10', 20-30 senconds at f/11 in 12x16''), and in any case I think it is negible in the levels I use.

Sirius Glass · Dec 28, 2017

halfaman said:
Cyan dial is there in the enlarger, why not use it?

I use always cyan filtration and I don't see any problem with it so far. It is the filter I use less, in the range of 10-20ish points in Durst scale while magenta and yellow are in 70-80ish, but prints behaves consistently with the adjustments.

If you add Cyan to Yellow and Magenta filters you have just added a Neutral Density filter to the mix. That is why the Cyan filter is not often used.

pentaxuser · Dec 28, 2017

halfaman said:
The main advantage for me is clarity. I use three dials for three different corrections, not two dials for three different corrections. .

It appears that you believe you get something extra by using the cyan filter but it is not clear to me what that is. It might help if you can say what by using all three filters at once you get which you do not get with only Y and M

This may help to clarify matters. Thanks

pentaxuser

halfaman · Dec 28, 2017

When I mentioned "clarity" it was referring to me.

I manage myself better having each correction in a separate dial. It is just more clear for me, nothing else.

DREW WILEY · Dec 28, 2017

Type R papers were common in the past for positive printing. You might need it for certain kinds of film exposure on the easel. And the feedback circuitry of some commercial colorheads selectively tweaks all three channels to accurately maintain a very specific quality of even "white light". This can make a difference even when fine-tuning a color neg RA4 print.

Marameo · Jan 3, 2018

So with the right filtration I can white balance daylight film shot under tungsten lighing?

RPC · Jan 3, 2018

Marameo said:
So with the right filtration I can white balance daylight film shot under tungsten lighing?

It can work to some degree, but daylight film exposed to tungsten light generally means the blue sensitive layer will be underexposed. Parts of the image which would nomally fall on the linear portion of the blue/yellow characteristic curve will fall in the toe region. This cannot be corrected when color balancing the print.

Why magenta and yellow filtration

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