Screening doesn't seem to work properly

[Adam_C._Smith@adobeforums.com]

According to the documentation, a black color screened over some base color (using the "Screen" transparency setting) should show the base color unchanged. But this doesn't happen; the base color still gets modified in some way or another.

The help file says that a black with just 100% K won't work right, and says to create a "rich black" and use that instead. So I've got a black with 100% each of C, Y, and M. But when I screen this over something it changes the base color. I've tried varying the value for K (still keeping the other three at 100%, so it's still some kind of black) and it still doesn't work right.

It only works properly if the base color is something fully saturated: pure C, pure Y, pure M, or some combination of those. If ANY of the C, Y, M, settings are anywhere EXCEPT 0% or 100%, it doesn't work.

What am I doing wrong? How exactly do you get a true black screen?

Thanks.

[Adam_C._Smith@adobeforums.com]

Addendum:

Playing around with the CMYK sliders for the "black" screen, I almost get the feeling that I could make it work if I could slide them up past 100%. Is there some kind of color-management setting I need to fiddle with?

[LenHewitt@adobeforums.com]

Adam,

You will find that the screen blending mode works as per the Help file only
when in RGB mode.

[Larry_Grohman@adobeforums.com]

"So I've got a black with 100% each of C, Y, and M".

I know this is not what you asked, and I don't want to start a debate on
which mix is the best Rick Black, but I can tell you that the mix you are
using will be problematic on offset press. 300% is a pretty common ink
limit, and some applications such as newsprint are much lower.

Depending on the RIP and the configuration, excess ink percentages could be
clipped back to required limits.

And as Len pointed out, RGB blend mode should fix your problem. I know that
sounds off base to suggest RGB mode for a print workflow, but it does seem
to work

Larry