Tilt shift – Color loss in CMYK file with 100% black background

[PiaLrs]

The file I would like to apply the Tilt Shift filter to contains a black background (C=0% M=0% Y=0% K=100%) and a cyan graphic (C=100% M=0% Y=0% K=0%). The graphic is to be processed with the Tilt Shift filter so that a soft fade is created. However, as soon as I apply the filter, the fading sides not only become transparent and blurred, but lose their color and turn white.

When I do the same in an RGB file, the effect works, but when I convert the final file to CMYK, I have a four-color black instead of a 100 percent black. So for printing this solution is not the goal, because the ink application becomes too high. If I now replace the black background with a 100% black, the colors in the tilt shift gradient are lost again.

It seems that the filter needs the color information from the background, but can this really be? Is the filter perhaps not usable for CMYK? Has anyone had a similar/the same problem and know how to work around it? Is there possibly another, more correct filter/application?

I would be very happy about an answer, we have already tried everything. Thank you!

[c.pfaffenbichler]

Please post meaningful screenshots. 

[PiaLrs]

Sorry, here we go:
How it looks like vs. how it should looks like

[c.pfaffenbichler · Accepted solution]

You decided to work in CMYK so please let’s not pretend the ensuing problems are mysterious. 

To illustrate: Make a Gradient Layer from 100/0/0/0 to 0/0/0/100 – the middle probably looks greyish, too. 

You might be able to alleviate the problem with a little trapping and/or a Curves Layer to »push« the Cyan. 

[PiaLrs]

Making the problem clear helped me a lot and of course you're right. The use of the gradation curves has brought me in any case already in the right direction, thanks for the tip!

[c.pfaffenbichler]

»the fading sides not only become transparent and blurred, but lose their color and turn white.«

That would seem to be as expected (though it is rather grey than white) and is owed to your decision to work in CMYK for this. 

CMYK doesn’t have true black so when reducing Cyan on the one side and reducing Black on the other the middle is »muddled« and the same thing happens with Gaussian Blur for example. 

[PiaLrs]

First of all – Thank you for the quick reply.
So it is due to the use of a blur-filter, no matter which one is used, do I understand correctly?
I would make the whole thing in RGB and convert it afterwards, but then I have the four-color black I mentioned, which is too much ink for the print application. Can you tell me how to convert the black background to 100% black (CMYK)? The correction via "Replace color" did not work so far.

[c.pfaffenbichler]

»So it is due to the use of a blur-filter, no matter which one is used, do I understand correctly?«

Any Blur or gradient between CMYK primaries will be affected. 

»I would make the whole thing in RGB and convert it afterwards, but then I have the four-color black I mentioned, which is too much ink for the print application.«

What is the correct CMYK Space for the print process in question?

Did you convert the RGB image to it or just go Image > Mode > CMYK?

If the latter what are the Edit > Color Settings? 

[PiaLrs]

I have tried several ways:

In variant 1, the original file was created in RGB, processed with the Tilt Shift filter and then converted to CMYK via Edit > Convert to Profile > Coated FOGRA39. I also tried various conversion settings, but apparently I didn't find the right one.

In variant 2 I saved the RGB file as jpg and converted it to CMYK via Edit > Convert to Profile > Coated FOGRA39.

With variant 3, I directly built up everything in CMYK, but then the problem already became visible when using the Tilt Shift filter. So I discarded the latter.

The two first variants work so far that the color representation is almost correct also after conversion, but the background color is just four-color black (C=74% M=65% Y=63% K=81%).

I hope I could answer your questions completely and correctly (English is not my native language).

[c.pfaffenbichler]

I think Fogra 39 has about 330% TAC – is that really a problem? 

What is the print process and what is its CORRECT CMYK Space in your location? 

What is the permitted TAC? 

[PiaLrs]

We also assumed that the existing TAC of 229% would not be problematic for the corresponding print application. However, the print company has now informed us that they would like to work with 100% black in order to be able to guarantee a clean realization (with regard to the negative text (white text on affected image)). Since we are not creating the print product for ourselves, but for a customer, of course we want to accommodate this. Unfortunately, this is all the information I have received from the print service provider so far. We are merely the implementing design agency and the customer's selected service provider is difficult for us to reach.

[c.pfaffenbichler]

»However, the print company has now informed us that they would like to work with 100% black in order to be able to guarantee a clean realization (with regard to the negative text (white text on affected image)).«

If it is requested then there is nothing to be done but accomodate them, I guess … 

If you cannot fix the problematic areas otherwise you could try working in RGB, converting to a Custom CMYK with Maximum GCR and then make sure the M- and Y-Channels are clean and the C- and K-Channels reach deep coverage. 

Custom CMYK is not recommendable in general, in some cases it might still be used. 

Can you provide the image?