grayscale Image results in PDF from Indesign

[Jean-Claude_Tremblay@adobeforums.com]

When document contain grayscale image, I have noticed some difference in
the results when creating PDF base on my choice of color conversion or
either I Export it to PDF or Print it.

I wonder why... please bear with me:

- My doc are CMYK with some Grayscale image (TIF, PSD or EPS all do the
same results).
- No Transparency Involve in the document
- Color Setting North American Prepress 2

Now the grayscale results (from the info in the PDF with Enfocus Pitstop:

1a) Export as PDF (Default PDFx1a), Convert to CMYK[Preserve Number] -
the image is a [Device-N, 1 spot Monochrome Black, alternate space CMYK]

1b) Export as PDF (Default PDFx1a), Convert to CMYK - the image is a
[Device-N, 1 spot Monochrome Black, alternate space CMYK]

1c) Export as PDF (Default PDFx1a), No Conversion - the image is a
[Grayscale]

When Printed to Adobe PDF 7 printer, with PDFx1a Setting also set to the
same color setting:

2a) Print - Output Color - Composite CMYK, the image is a [Spot Black -
1 Spot Monochrome Black, alternate space 0%C, 0%M, 0%Y, 100%K]

2b) Print - Output Color - Leave Unchanged, the image is a [Grayscale]

My simple question, why does the image results for the grayscale image
is differents.

2a) is the one that give us problems on one of our rips. (The image rip
inverted).

Jean-Claude

[Leonard_Rosenthol@adobeforums.com]

The different between Export and Print is obvious - when Exporting, ID is able to do a richer handling since all the data is present. When printing, things have to be brought down to the "lowest common denominator".

Now, as for 1a/b vs. c - I don't know. Sounds like a good question for the ID folks.

Leonard

[peter kleinheider]

Dear Jean-Claude,

When you convert to CMYK (no matter if printing or exporting), InDesign will ether change the image to Separation Black as DeviceN. This is usual not a problem.

But you are right. Some Rips treat DeviceN Colors as SpotColors or treat them different than DeviceCMYK or DeviceGray. I have also seen some color conversion products, that do not touch CMYK colors, if they are defined in DeviceN, which is not correct ether.

From a technical standpoint it is just a different way of defining the same color in a PDF - maybe Leonard can comment on this. It should not be of any concern for the end user if the PDF would get interpreted correctly.

BTW: if you set a Grayscale image to overprint, it has to get converted to Separation Black, otherwise it will not overprint any other CMYK elements.

rgds

Peter

[Jon Bessant]

Indeed, when it comes too using DeviceN within applications such as
Pitstop, some great conversions can take place.

For example, a CMYK image can be convert to DeviceN with CMYK defined as
spot CMYK (as such).

From here you can run an Action List to either remove or remap these
colours ... new to Pitstop 7.

Yes, certain legacy renderers can choke on these (spot) process colours,
an update should certainly overcome these issues you might be
experiencing ... or create a workaround within Pitstop to change the
colour space (although by testing different output methods with your
renderer you might find a happy medium) ...

Jon