Rich black : faded gray appears colored

Question

I have a question about using rich black for a print document. In InDesign, I set a rich black color for the background (0/80/0/100), and I need to set a faded round gray shape, with an opacity around 30-40%, on top of the black background. I create this shape in Photoshop and import the PSD file in InDesign.

Issue : as the rich black contains Magenta, and the gray has transparency on top of it, it appears colored (because of the Magenta in the mix).

Is there a solution to make the gray actually gray on top of my rich black background ?

Thank you very much !

Answer 1

I don't know why you choose that rich black combination in the first place. You probably don't want a neutral gray but a warm red.

Also, when doing a print job you can simply use the values of the colors you expect, not a transparency which, depending on the ink and blending modes you use, throw different results.

A neutral rich black, needs to have some characteristics.

1) The added colors besides the black, need to give a neutral gray. That seems obvious. In this case if you remove the black it is clear you dont have any neutral grey.

2) In a neutral CMY gray you will find simmilar values of magenta and yellow (red), but you will find more cyan. This is becouse you have 2 inks to neutralize with one.

For example. In the rich black resulted of aplying the Swop color profile, gives you C75M68Y67K90. See how you have more cyan?

A color profile is a complex algorithm

If you have some color gradients in rgb and you convert them into a cmyk file you don't have linear conversions. The first darkening of a tone is performed by a complementary color. After some point the black ink comes into play, not in a linear way either.

This algorithm (and resulted cmyk values) also depends on what paper you are using for printing.

You can read some explanations here: http://otake.com.mx/Apuntes/RGB-CMYK/RGB-CMYK-5.htm It is in spanish, but you can use google translate.

The options

1) Make your gradient in rgb and convert it after to cmyk using the correct profile.

2) Make a rgb gradient as a test. Extract the values of the neutral gray you need, and make a gradient using thoose values, at least for the CMY part and play with the black as you like.

Don't go beyond the total ink your profile is recomending.

Answer 2

Because of how you black is being decomposed, you'll always see the other tone when using a rich black, especially if you use high density of colors other than black in your recipe.

As you know, your rich black has a large tint of magenta, it's totally normal the gradient will look a bit brown.

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In Photoshop, the only way you could achieve what you want is:

1) by lowering the density of your magenta and adding some other color to compensate and neutralize it in the gradient.

For example, C30-M60-Y20-K-100. If you need to keep that M80 value, then raise up the other value in an equal way but no more than your 300 density.

The gradient will always remove every tone in a proportional way. You cannot have a rich black heavily tinted with magenta and gradients that go to pure black in the lower density, but you can neutralize that effect by enriching the other colors in your black. Whenever you use a rich black, you also have no other choice to choose which tint your black will be and which tone is acceptable for your layout.

But maybe you really need that exact recipe of rich black for some reasons. The option #2 might work for you then.

2) You could adjust the curve or levels of your magenta in that gradient.

But this might end up creating a zone where the magenta will be more visible and your gradient might look less consistent because of the drop in density. To help on this, you can still add a bit of the other C-Y color to hide that effect, especially if you are working on a print-project.

It's still possible to adjust this lightly to at least remove the magenta in bigger proportion in the lighter parts of your gradient and keep more percentage of black there instead. This should make the magenta less visible where the gray is lighter.

You need to be careful to not drop the magenta too brutally in your levels if you work on print projects, this effect might look amplified once printed.

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More details here on rich black and normal black in printing, and some extra tricks.

Answer 3

If you want the grey color to show, then you can't change the overlaying object's opacity to do it, as that will always result in the color behind showing through. My first choice would be to build the grey fade into the Photoshop doc, but if you must do it in InDesign, then you should save the grey object as a gradient in Photoshop from opaque in the center to transparent at the perimeter. Using a blurred mask (and no background layer) is probably the easiest way to accomplish this. (This can be simulated with feathering in InDesign, but the result is usually banded) Place the result (saved as PSD, TIFF, or PNG) over the black build in InDesign and you should see something more like what you're after. Note: There will inevitably be some pinkish tinge in the gradient because your build is heavily magenta.