Conversion from RGB to CMYK loses mesh gradient transparency

Question

I purchased and adapted a vector graphic in RGB that I want to send to a printing bureau. The directions state:

When uploading:

• Convert text to outline
• Remove template lines before saving
• Keep the provided file dimensions
• Use 300 dpi as native resolution
• Apply FOGRA 39 color profile
• Avoid cropping marks and color reference bars

The conversion of the emojis from RGB to CMYK works fine when they have simple gradients but not with mesh gradients.

The graphic in Illustrator CS5.1 looks like this:

When I convert te document to CMYK, I lose the transparency in the mesh gradients:

If I rasterize the emoji, I lose the transparency around the edges. If I rasterize the whole image at the required 300 dpi the result looks poor:

How can I convert from RGB to CMYK and keep the transparency of the gradient?

update

The gradients in the original file are vectorial and use "screen" overlay mode to shade the underlying color:

I would rather not rasterize a vectorial document for printing. If I can't fix it, I'll remove the gradient meshes, but they had a nice touch and I would prefer to have them in.

second update

I believe that the problem stems from the transparency overlay modes in RGB and CMYK. The mesh gradient has "screen" mode and it works in RGB and not in CMYK. Of all the available modes, the only one that seems acceptable in CMYK is "color burn" (see picture with the selected mesh), except that the result is a more saturated color instead of a lighter color.

So I believe my only options are to rasterize as is, or to redo the mesh gradients from scratch, right?

Answer 1

The issue is not actually transparency in its true form.

The issue is the Screen blending Mode.

Some blending modes are not supported in CMYK. See Here for "why"

Straight transparency, without any blending modes, converts to CMYK fine.

You will need to remove the Screen mode and manually adjust the meshes so that blending modes are not necessary.

Using transparency is fine, but without the blending modes. You'll need to set all the mesh points to the same color, then change the outer mesh points to be transparent. You'll get generally the same overall appearance.

While not related to meshes this similar question relating to standard gradients with the same issue may be helpful

Answer 2

Try one simple thing.

If the vector file has initially RGB colors, export the image as RGB with the desired PPI.

As a second step, convert it to CMYK.

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Remember to save the CMYK file in a file format that maintains the overall transparency, like TIF or PSD in case you need it for some additional step.

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Edit.

In most cases, the best option is to rasterize, in some is the ONLY option. But let me assume that you need to keep some parts in vector.

I would brake the image into two parts.

Detach all the black parts. Then rasterize all the gradients in RGB mode, convert it to CMYK mode, and put over it the black vector with your CMYK values.

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But the truth is that is probably too complex and not worth it. I do not know how small the image will be, or what kind of print you are doing. But in almost any case, a raster image at 300PPI is more than enough.

The only things you really need to keep as a vector is text and only if you have on pure black ink (or 100% of one ink). The rest can be rasterized, depends on the project.

Answer 3

Thanks for the edit to your question.

I don't think there is an automatic way to do this. Sorry. It looks like you will need to edit the gradient meshes manually to add transparency to parts of the mesh.

Also, it might be possible using blend modes, but I'd avoid these if possible since blending modes can also be problematic.