There is absolutely no doubt that submitting finished artwork as PDFs has eliminated several prepress issues such as missing links and (mostly) missing fonts. Sadly, it has not eliminated all prepress issues associated with submitting artwork. In this post, I would like to look in more detail at an issue which is to me a fundamental step before submitting finished artwork, and that is checking colour separations in a PDF – properly! Not doing so is a cardinal sin of prepress.

For this, I have created a mock-up black and two spot colour flyer for a favourite destination of mine, Montréal. On face value, the PDF appears to be fine, but after looking at the artwork in more detail such as the crop-marks and where the artwork bleeds, it is clear that the bleeds will need to be fixed.

This is issue one. The rest is fine, right?

No! To see the other issues, the output preview dialog box has to be open. To get there using Acrobat 9, go to the advanced tab, then print production… , then output preview

Suddenly, the preview changes a little. From here, it is possible to see checkboxes for both process plates and spot plates. This job is Black plus two spot colours, so all appears to be right so far… but what happens when the black channel is turned off?

Instead of disappearing, the black becomes lighter. This means that the black is not purely on the black separation, but rather all of the process separations. It should look like this:

So what is going on here? It would appear that the blacks are actually made of process despite appearing greyscale, the photograph may have been RGB or CMYK. The type, despite appearing black, may be made using RGB black. So how can this be determined?

In the output preview dialog box, there is a dropdown which says “Show”. By default, the dropdown result is All, and this means that all gamuts on screen are shown, but not necessarily what images are process, spot, RGB or LAB.

If the dropdown field is changed for example to RGB, it is possible to see what items on the page are RGB only.

After doing this, it appears that the type on the page is RGB which is why it isn’t colour separating properly into black. This means going back into InDesign and changing the RGB black to 100% Black. OK, one issue, but what about the masthead picture – that isn’t RGB. It is possibly made of a “faux black” out of process, so the dropdown needs to be changed from RGB to CMYK.

I can now see two things: what appears to be a black and white picture, and coloured type in the left middle of the page. To determine if the black and white picture is actually on the black separation only, the black separation has to be toggled off.

The image has become lighter, but not disappeared. This tells me that the image is made out of process instead of being greyscale. This means going into photoshop, making the colour mode greyscale, resaving, relinking in InDesign. That is two issues.

But why was there process coloured type? It should be two spot colour separations plus black. To check this, change the dropdown field to spot colour.

Now I can see the word Montréal in solid 494, the background in a tint of 494, and the strip of yellow 610. But the words “WHEN SHOULD I GO?” have disappeared. This infers that these items were not made out of spot colour, or they should be visible in this view. Instead, the items must be made out of process, as they were visible in the CMYK view, but not Spot Colour nor RGB views.

So after checking the PDF and its separations more thoroughly, I now know there are several fixes required for this PDF: The InDesign file needs to have the following changes:

• Colour which extends past a trim area has to bleed off;
• The RGB black type needs to be 100% black only;
• The “black” photo of Montréal needs to be made greyscale;
• The words “WHEN SHOULD I GO?” and yellow strip behind need to be changed from process to their appropriate spot colours.

I have prepared before and after PDFs for the purposes of trying what has appeared on this post.