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Nikon Coolpix P900 Review

The Nikon Coolpix P900's claim to fame is its 2000mm equivalent optical zoom. In this in-depth review, Bob Atkins examines the pros and cons of this new addition to the superzoom bridge camera...

Magenta, Yellow, and Blue

Beth Kerkendall , Nov 26, 2010; 12:32 a.m.

I was wondering what would happen if the magenta, yellow, and blue all were turned up on the enlarger? Would it make the image all black? That's just my guess. What if magenta was turned all up or just one of all the colors. I wonder what that would look like.


Leigh B. , Nov 26, 2010; 12:56 a.m.

Yellow is "minus" blue.

White light has red, green, and blue components. Yellow is red + green, i.e. white minus blue.

If you turn up both yellow and blue you'll get white (perhaps tinted, depending on the ratio of the colors and the accuracy of the filters).

Magenta is red + blue, thus white minus green.

Since I don't know what kind of image you envision, I can't answer your question.

- Leigh

Robert Chura , Nov 26, 2010; 12:57 a.m.

Basically if you use equal amounts of each they would end up like a neutral density filter and just make a longer exposure.

Frank Schifano , Nov 26, 2010; 07:29 a.m.

I suspect we're talking about what happens with variable contrast papers, because with graded papers the only thing you'll accomplish is to increase your exposure times. If you turn the agenta all the way up, you'll get as hard (high contrast) an image as the particular combination of your paper and enlarger can deliver. Conversely, if you turn the yellow all the way up you will get as soft (low contrast) an image as possible. If you turn up the cyan, or what you call blue but really isn't, you do nothing. Cyan is a combination of blue and green, the colors to which the paper is most sensitive. Dialing in equal portions of magenta yellow, or magenta, yellow and cyan, acts as a neutral density filter and behaves the same as white light only less bright. OK?

Alan Marcus , Nov 26, 2010; 07:37 a.m.

First, the filters used on a color enlarger are CYAN, MAGENTA and YELLOW. These colors are chosen because color photo paper contains three emulsion layers. One layer is sensitive to red light, one to green light, and one to blue light. When we print we need to adjust independently, the intensity of the red, green and blue exposing energy. We use the lens aperture and exposure time to control all three layers simultaneously. This controls the density (darkness / lightness) of the finished print.
In every case, it is unlikely that the finished print will have the correct color balance (color cast). We fine tune by adjusting the color correcting filters that are either built in the enlarger or physically placed in the path of the exposing light.
We need filters that independently adjust each of the three primary colors. The cyan filter is red blocker. The higher the cyan value, the more red that is prevented from hitting the paper during the exposure. The magenta filter is the green adjuster. The yellow filter is the blue adjuster.
Now the filters used vary in their correctness. We can make a near perfect yellow filter. This is a filter that passes red and green while adjusting blue. We can make a reasonable magenta filter. It should let blue and red pass and block green in increments based on the value selected. However the best magenta filters we can make also block, in error, some of the red and some of the blue. In other words the magenta filter has some inefficiencies.
Now the cyan filter is the worst. It should pass green and blue and adjust red. Sorry to report it is very inefficient. So inefficient that we avoid its use when color printing. To accomplish, the color negative film is biased so the green and blue exposing light will always be in excess. We print using magenta and yellow only.
Since magenta is a green blocker and cyan is a red blocker and yellow is blue blocker, if we deploy all three in equal amounts we are blocking all three primary colors. This is the same as stopping down the lens. In other worlds upping all three induces neutral (gray) density and the result is under exposure. We can compensate by increasing the time of exposure or by opening up the enlarger lens.
So the simple answer is: Upping all three color correcting filters reduces the light on the easel and this will cause an under exposure and the resulting print will be too light.
Let me add that under certain circumstances, we do print using cyan. This might be necessary if the color film has a very unusual color balance.

Beth Kerkendall , Dec 02, 2010; 04:53 p.m.

Thank you guys, and my bad, I forgot it's called cyan. I'm printing with black and white film, not any image in particular, but was just wondering what happened. When I did all the colors up, I got a blank piece of paper, ha ha. So thank you for the information.

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