: Color mode problem for selecting colour in cmyk Is it compulsory for good result to choose a zero value in either of any four c, m, y or k. In CMYK, can't we select a colour which is

@Debbie163

No, you can use whatever values you want in CMYK, as long the total of the 4 values don't go above 300 ideally (for offset printing.)




I heard that cmyk should be only a three colour process for good
printing. So that's why I was asking whether it's necessary to take
zero as a value in any c, m, y or k. eg - If I want to take a brown
color value as c-40, m-70, y-100, k-50, but there is no zero in any c,
m, y or k. So should I choose this colour or not??? will it come good
in printing??? Hope I am able to explain better this time?


Large area printed with 1 color

There's one reason why it's not a bad idea to use the 4 colors CMYK in SOME colors; it's to avoid the "stamping" effect on offset. It can happen when printer have to print large areas with the same color.

Example of "stamping" effect:



But this is generally helpful when you use a 100% value for one primary CMYK color; by mixing 2 and more, you can get a better finish and it's easier to print for the press operator. It's a bit like applying coats of paint on a wall; when you use 1 color only and this color is very "thick", you will see the roll stamps on the wall and will need 2-3 more coats. On offset press, it's a bit the same principle; the other separations will act as the extra coats.

But the same issue can happen with 1-color Pantone printing and there's nothing you can do about it besides not using a 100% color on a large area; it's up to the printer to update his equipment to avoid this and it's also affected by the way they impose your artwork on their large sheets! It happens more often when the rolls on the press need to be changed and when there's big areas that are printed, and some white areas in-between.

Besides the rich blacks and light grays (or light M-Y-K or Pantone), you shouldn't force yourself to use values that will change your colors unless you want to.



Light gray or light 1 color separation

There's also very light density colors such as light grays that might look better if you enrich them a bit with the other CMY; this way it will hide the halftone pattern.

If you use only black (K) for a light gray, you might notice the little dots on the final printed sheet. The lighter your 1-color separation will be, the more distant and small the dots will be, and the more visible that effect will be as well! So that's one other situation when you should add a bit of the other color separations in your mix. The higher the LPI (print quality) of the offset press, the less it will be apparent.

This starts being more of an issue for density below 10% in 1 color only though. There's nothing you can do about it if you use a Pantone or 1 color print job besides using a good quality printer or having your densities above 10%. Or using digital printing!

Example:



So that being said, you only need to be careful for light colors using 1 color separation or 1 pantone in general. And yes, in general, print operators don't like big mass of ink that uses only 1 color! I think that's what they hate the most actually, so if you can, you help them a bit by enriching your color IF it doesn't change your design.

It's usually very easy to calibrate a press when the colors have a nice rich density or bright colors, or a mix like the brown you described; anything skin tone, light tone, pastel, beige, sand is greatly influenced by a 1-2-3% change in the calibration and is more challenging to print on offset because a little extra in one of the other separation can change the final result dramatically!



Have a look at my answer thee, there's an explanation on "stamping" and also rich blacks:

What kind of black should I use when designing for CMYK print?



Source image offset gray: www.tkcups-sorgs.com/UI/Informations.aspx?i=gi

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@Si6392903

This is a color theory issue.

In theory if you have lets say an orange (M50Y100) and if you add cyan you are neutralizing the saturation.

For example a neutral gray could be* a C50M50Y50 K0 or C0M0Y0K50.
*(Thoose are not the exact values, I'm just posting that as an example)

But in practice if you reduce the 3 primary colors you reduce the posibility of a color shift in tone.

For example. If you add cyan you could shift a light orange to a greenish yelow if the print adds too much ink in the cyan channel.

You can see here you have the risk of passing thru the green part of the circle just adding cyan.
otake.com.mx/Foros/UsingComplementaryColor.png
If you darken a color with just black you just make it darker, not greenish.

All that in the case the print house has little control on the process. If it has a decent quality this risks are reduced.

For example almost all spot colors are defined in a combination of all channels. Again this is asuming the press has good quality control.

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