How to remove everything from Yellow Separation

[prepressman_ntsf]

I have a project where we created a 5.5 x 8.5 phone with white and yellow pages. We are not using yellow for the yellow pages, but flooding the sheet with a 40% screen of yellow. The designer did some elements as duotone, and they are showing up on the yellow separation.

I attempted to create an action list to resolve this, and here are the steps I thought might work:

+ Copy the 40% Yellow screen and add to a "Add copied graphics" action

then run an action list that does the following:

1 Remove the original yellow screen on every page
2 Convert the entire document to greyscale
3 Add the 40% Yellow screen back with the "add copied graphics" action to the background

This did work, however, not exactly as I had wished because of the layering and duotone effects the designer implemented. Some elements would be complicated to resolve. Some of the images could be set to a transparency of multiply, but other elements would require more work.

My question is: is there a way to select all the type and images on only the yellow separation and remove them?

I could then run an actions list that does the following:

1 Copy the 40% Yellow Screen
2 Remove everything on the yellow separation
3 Add the 40% Yellow screen back with the "add copied graphics" action to the background

Thanks for any help with this!

[freddyp]

Can you be a bit more specific on

The designer did some elements as duotone, and they are showing up on the yellow separation.

Which colors were used in the duotone? Black and yellow? How do some elements show up on the yellow separation? Do they knock out the yellow?

Can you share a (simplified) file?

[magnussandstrom]

We are not using yellow for the yellow pages, but flooding the sheet with a 40% screen of yellow.

I guess you missed to type out the word "paper"?

Could you provide a sample file, and maybe a screenshot of how the design element are affecting the 40% yellow tint?

[prepressman_ntsf]

The white pages and yellow pages was meant as an American phonebook term for the white paper and yellow paper, respectively. If you had a phone book you went to white pages (black ink on white paper) for individuals you knew and yellow pages (black ink on yellow paper) for businesses.

The duotones consists of yellow and black.

You can see below that in the Yellow separation, that part of the yellow image she created is showing up on the yellow separation. It has densities of yellow greater than the 40% yellow screen.

The reason this was an issue is that I wanted to create a commonly shared yellow plate, and this image was showing up on forms on the press that did not have this image present and you could make it out the yellow impression made.

Yellow Separation only

yellowpage 1_yellow sep.JPG (40.81 KiB) Viewed 157583 times

Black and Yellow

yellowpage 1.JPG (191.28 KiB) Viewed 157583 times

[loicaigon]

If you can spot the yellow pages in some way or the other, you could select those pages, combine with Select Images and remap Yellow channel to "None".



It depends how your 40% yellow screen is made of (vector or image), because if it's image, you may need to exclude from the remapping.

[magnussandstrom]

This issue could also stem from the blending color space, the properties of the shadow object, or RIP settings. The simplest solution might be to create a separate job specifically for the yellow plates. However, it's always interesting to dig a bit deeper, perhaps you could share a link to the PDF page?

[JimmyHartington]

Could a solution be to first remap yellow channel to none as Loïc suggested.
Then add a 40% yellow rectangle in foreground with multiply set as blending mode?

But as Magnus suggest it would be easier to try with some test-files.

[prepressman_ntsf]

A link below is for the file if anyone would like to take a look. I realize that the easiest way to resolve this would be to as magnussandstrom suggested would be to create a separate job specifically for the yellow plates, but the troubleshooter in me wanted to see if what I presume can be done in Pitstop is possible.

https://www.dropbox.com/scl/fo/7a0b9p1b ... ge32l&dl=0

Because she has text and images set to 40% yellow to match the 40% yellow screen in the background (that emulates yellow paper) when I have the action to remove the yellow page and convert everything remaining to black, those yellow elements appear white, which is not what I want.

Below is an image of p. 91 where you can see that an image with a 90% black screen applied to it shows up on the yellow plate. After my current action steps, however, this does not appear to be an issue.

page 91_90 percent black.JPG (22.64 KiB) Viewed 156784 times

page 91.JPG (63.08 KiB) Viewed 156784 times

On Page 80, the outlined numerals "506" contains 20% yellow and 50% black. After my actions are run, the numerals are no longer there and the frame around the advertisement (it has about a 1pt rule around it) disappears.

These are only some examples.

Here is a link for the action list I created as well:
https://www.dropbox.com/scl/fi/yjv48h98 ... cwnie&dl=0

[prepressman_ntsf]

Here is another example of what happens after I run the action steps (See below). On this page many elements disappear and the black images no longer blend with the yellow beneath.

current actions results_p64_beforehand.JPG (95.35 KiB) Viewed 156784 times

current actions results_p64.JPG (56.67 KiB) Viewed 156784 times

[JimmyHartington]

I have made an action list.
It remaps the yellow channel to a spotcolor with alternative CMYK as white.
Remaps this color to CMYK.
And then adds 40% yellow on top with multiply.
You can find the action list here: https://github.com/jimmyhartington/pits ... tiply).eal

[prepressman_ntsf]

Hi Jimmy,

Thanks for the action list--it appears to work!

I am attempting to deconstruct/comprehend how this works. I recall someone, maybe yourself, saying earlier to remap the yellow channel to a spot color. Does it matter what spot color or just any spot color?

What is the alternative CMYK? Are those the white elements that were in the file? Are you then remapping the white to cmyk?

I am using an older version of Pitstop, but I believe I am in the correct place to perform the actions you have described.

remap-to-yellow.jpg (48.28 KiB) Viewed 138193 times

[JimmyHartington]

The trick I used is to remap the yellow channel to a spot color.
This spot color has to have an alternative CMYK value of C 0%, M 0%, Y 0% and K 0%.
Because the next step is to remap this spot color back to CMYK. So the spot has to be white.

Last bit is to then add yellow rectangle on top with multiply (should also work if overprint fill was set to on).

Acrobat-megatrade.staging.dynamicweb-cms.com-2025-04-29 at 23.05.26@2x.png (245.96 KiB) Viewed 137267 times

[freddyp]

I have one (pedantic) remark about the use of the multiply blend mode for the 40% Y rectangle that is placed on top of the page. When there is yellow somewhere in a design on the page that has a percentage higher than 40, multiply will result in the highest value, so the yellow will not be a uniform 40%.

The question here is how you want to interpret that? If the 50% yellow of a text for example has to be respected, then using multiply is correct. If that is an error and the yellow should be 40%, then you should use overprint with OPM1. The behavior of this is that the black will shine through, but any yellow underneath the 40% rectangle on top will be knocked out by that 40%, and the result will be a uniform 40% yellow.

If nobody ever creates yellow with a higher value than 40% then this is purely an academic point.

I still have one (less pedantic) remark about the method of placing the rectangle. You are using "Add copied graphics" for this. I would suggest to use "Add object - Rectangle", use one of the page boxes for the size, and the color is of course a fill of 40% yellow. Follow up with "Select last added objects" and change the blend mode to multiply, or change the overprint settings, as explained above. It is a lot easier to configure, the size is always correct, and the properties of what you are placing are explicitly defined, rather than implicitly as part of the copied graphics.

[JimmyHartington]

Hi Freddy

Nice with some input.

The choice of multiply was based on the previous steps, which remaps the current yellow to white.
And that not all viewers as standard has overprint preview enabled.
But I can see the logic behind using overprint.

In regards to the placing of box on top was just based on pure laziness
I had a box in the pdf with multiply applied. So it was just the fastest way to send an answer.

Here is a new action list, where I still start by remapping the yellow.
And then adding a rectangle based on the bleed box with 40% yellow overprint on fill in OPM1 mode.
https://github.com/jimmyhartington/pits ... ply-v2.eal

[MURNMO]

<Add 40% yellow on top of page (Multiply).eal> has been improved a little.