One of the many stumbling blocks of print design is the interaction of transparency and spot color. It’s a rather demanding subject and impossible to cover completely in a single blog entry. So, let’s confine our discussion to the realm of the PDF/X1a. And, just to keep things simple, we’ll use the same BPI banner art from the previous blog posting.
First, let’s take a look at the Spot_Color screenshot below. As you can see, the BPI logo, headline and web address all share the same value, a variation of the legacy version of Pantone Reflex Blue-Coated spot color. Notice that the spot color objects are uniformly close to the top of the stacking order with only solid objects like the white BPI and green leaf with a solid white stroke above them.
Now, lets take another look at the PDFX/1a version of this art (screenshots Spot_Color_PDF and Spot_Color_PDF_Outlines). Despite the lack of transparency. The automated PDF engine has created several slices and clipping masks. But because there are no interactive transparent objects, the slices still retain their original color value of PANTONE Reflex Blue 2X CVC 2.
Now, let’s screw this up. Let’s add a drop shadow to the white portion of the BPI logo. We’ll use the default drop shadow values (see Drop_Shadow screenshot below).
Please take note of the transparency values of Mode and Opacity. Next, we’ll save this art as a PDF version X/1a . Now let’s take a look at the results, see the Missing screenshot below.
Our drop shadow appears to have vanished and a few chunks of the logo have changed colors to the background blue. But wait, there’s more. The bpi has shifted away from a true white of 0 cyan, 0 magenta, 0 yellow, 0 black to something a little different – see Color_Shift screenshot.
If you think this is disappointing, take a look at how Acrobat views the same art (Acrobat screenshot). If you tried to print this file in a conventional RIP, the only thing you could count on is NOT getting what you wanted.
So how do you avoid this. Either avoid overlaying any transparent elements over objects with spot color or employ a different Acrobat preset. Just for example, here’s what the High Quality Print preset looks like – see HiQual_Preview screenshot. At last, everything looks exactly like it’s supposed to.
But the big question is, will the new PDF print correctly? Only your service provider can answer that question. And that’s going to depend on the capabilities of their RIP and print devices. If you have any doubts, call and ask. Everybody likes getting things right the first time.