Nick Hodge's Blog

In a world where composite PDF is the norm, this DCS workflow no longer fits. With simple CMYK work from Photoshop, placing elements and generating separations is simple. The graphic is still held as separate plates, but presents to the user as a composite image.

The problem arises, however, when attempting to take a CMYK+spot(s) file from Photoshop and attempt place into any application – including InDesign 2.0. Ultimately, it would be great to be able to place a single file that contains bitmap and vector information, as well as holding transparency and spot colours. Presently, the only file format that supports this fully is DCS. Whilst you can create Illustrator 10 .ai or .pdf files containing CMYK bitmap and spot colour vector objects, Photoshop is still largely the tool of choice for creation of special effects.

Photoshop allows spot colour channels to be created, but the only supported output formats are EPS, DCS and Photoshop PDF. In all of these formats, any transparency is not retained.

Therefore, this technique (which has been used in production) may assist you in combining the power of Photoshop and extending its spot channel support, and the power of transparency in InDesign to assist us in creating a printable job.

The process:

The overview is: create two Photoshop PDF files, place them on top of each other in InDesign 2.0. The bottom-most file is a CMYK only Photoshop PDF, and the topper-most file is a Spot-only Photoshop PDF. This technique relies on the Transparency Flattener in InDesign 2.0 to weave its magic to generate a composite output.

Step 1: create the source graphic element in Photoshop. In this example, we have a masthead that contains a Bevel&Emboss Photoshop layer style. Our goal is to make the colour of the masthead a special colour. (in the realworld example, this was printed as a metallic silver colour). Don’t create the spot channel yet. Save it as a Photoshop PDF (retaining transparency, vector information and resulting in a compact file).

In this file, the text has a white (or knockout) colour. Its goal in life is to act like a “cookie cutter” and remove the ink from underlying elements at print time. The Bevel&Emboss effect is created using a Black ink, so it will still appear on the black plate at print time.

Step 2: Take the same Photoshop PDF file:

• Turn off any effects.
• Change the white/knockout colour to Black. Choose a % of black that equals the % of spot colour ink you would like. In this example, as the element is a vector text element, it is just filled with 100% Black.
• double check and ensure where you have black, you want the spot ink to appear
• Mode>Convert>Grayscale. The will convert the black elements to 100% Black.
• Mode>Convert>Duotone. This will then permit you to change the Black to a named spot channel. Thankfully in Photoshop 6 or 7, this will be clipped inside the vector text element.
• For Advanced Users: you can also use other Layer Styles in Photoshop to ‘feather off’ the spot ink to create a highlight effect.

Do not make any position changes to the file. Set the channel in the Duotone to the same spot ink you are going to use in InDesign. This can be “Ink Aliased” at output time.

Step 3: As you will notice, saving as an EPS or PDF – transparency is not retained in this process. Don’t panic, we’re going to fix this in InDesign.

So we have two files: one being the Composite CMYK object saved as a Photoshop PDF, and another saved as a Photoshop PDF containing a Spot colour. In both files, there is vector data ensuring high quality output. In this example, I am using the .PDP file extension: the data inside the Photoshop PDF file is exactly the same; all I have done is adjust the extension. This will enable InDesign to Edit Original into Photoshop automatically.

Step 4: Go to InDesign 2.0. Place the file saved in step 1.

Step 5: Place the file saved in step 3, positioning it exactly over the top of the file placed in step 4. Use the transform palette to get 100% placement accuracy. Don’t worry about the “white” (knockout) colour from the placed file.

Step 6: set the top object to 100% Multiply using Window>Transparency. Almost magically, the white colour is removed, yet the spot colour remains. Leaving this at 100% Multiply, at output time the spot colour is retained (not converted to process)

To make the printing process a little more difficult, here the layer which the two elements are placed onto have been moved behind the image.

Step 7: Export as PDF, or Print to the Acrobat Distiller. In this example, I printed using Composite CMYK. Its a little difficult to fathom; but spot colours are held in this process (unless you use InDesign 2.0’s Ink Manager to convert them back to process at print time)

In the above screen dump, I am using Quite Revealing to show the background colour from the Composite PDF. As you can see, the first placed CMYK PDF ‘cuts out’ the colour in the background: in this instance, the PANTONE 264C Spot Colour.

This above screen dump shows the PANTONE 340 C as created in the second Photoshop file

Here is the black plate. The Bevel&Emboss added in the first Photoshop PDF is retained, and overprints the spot colour correctly.

How does this work?

The first file you place (CMYK) element acts like a ‘knockout’ element, removing any items underneath. The second file placed (EPS Spot) then overprints the underlying CMYK object. As InDesign’s flattener is smart, it does not knockout underlying elements. It also does not change their colour in the flattening as the top object is a spot colour. Other blend modes such as Lighten or Darken do attempt to change the colours – so the final document may be forced into CMYK.

What’s the Benefit?

What does this provide that DCS does not? The ability to generate a composite PDF. As soon as you place a DCS file into QuarkXpress, InDesign or PageMaker – you are forcing the output to be separations. In modern Postscript 3 or Extreme workflows, recombining preseparated output is difficult, and not the default workflow.

If you are in Australia, you may have seen the June 2002 issue of the Foxtel magazine. It used this technique. Supplied as a composite PDF with Spot colour, it correctly separated, was trapped and printed as a metallic. The Bevel&Emboss in the K plate overprinted the silver-metallic special colour. This plate is still a vector element.

Thanks to: Matt Phillips, Ben Hewitt (who tested this out on a live job!) and Alan Rosenfeld (for listening to my ranting about this in Brisbane). A big thankyou to Aaron Cliff from Foxtel magazine for sending a better quality image – and more importantly, being brave enough to pioneer this technique.