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I created transparent shadows in Photoshop. Saved (CMYK) as a .psd document. Opened it up in Illustrator and applied it under the main image. In Illustrator, it looks good (a slight darker shade of the background color).

Here's the problem. I had to also save it as a PDF. So I saved it from Illustrator as a PDF file (I tried a few different saving methods: Illustrator Default, PDF/X-1a:2001, High Quality Print, Smallest File Size, etc..) All have given me the same end result when I open the PDF file from Acrobat: When I open that PDF file, I get this grey shade either at the ends of the shadow or middle.

enter image description here

Can this be avoided? This is a print file for packaging and I have to show the PDF to someone and this will look REALLY misleading.

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  • Hi. Welcome to GDSE. This looks like what happens when you export an RGB document to a CMYK document. Try this: Flatten the image in Photoshop, save a copy, place this copy into Illustrator and make sure your Illustrator document is also in CMYK.
    – Billy Kerr
    Commented May 3 at 23:17

1 Answer 1

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You need to flatten the image first.

What you are looking at is an element of pure K channel transparent over a color object.

Here I have two gradients of a pure K black. One transparent normal blending mode and the other transparent but with multiply blending mode.

enter image description here

When flattened they react differently. The first one reduces the magenta and starts increasing black.

But the second one does not reduce the magenta, only adds the black on top.

Here are the magenta channel and the black channel.

enter image description here


The blending mode multiply is most likely not allowed in the profile you are using, so in order to merge the channels, flatten the image first..

If your bitmaps and objects are already CMYK See if it works by flattening the two bitmaps in CMYK mode with the black object as multiply.

If your images are RGB flatten in RGB and convert to CMYK later.


An additional note:

On rare occasions you can mess up a CMYK file, because you can, depending on the values of the CMYK channels, exceed the TAC.

If your underlying image has let's say C50 M100 Y100 and your top shadow has K100 the total ink will be 350% which is potentially more than your printer profile will allow.

P.S. 2. Make a backup of your work before flattening your image. I normally have two files.

  • ProjectName-01.ai
  • ProjectName-01-Output.ai

The first one is fully editable. The second one has a few steps regarding flattening raster images and shadows.

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