How to Grayscale a non-device CMYK file

[Brian_Hinther@adobeforums.com]

This may be a really basic question. In fact, I don't even know the difference between non-device CMYK and Device CMYK or if there's a way to convert one to the other.

What I do know is when I go to Convert Colors in Acrobat, my only option to convert from is Device CMYK. This works great when the document is Device CMYK. However, when the document is non-device CMYK, nothing happens.

Can someone please explain this probably very basic issue, and how to grayscale a non-device file? You would be a hero at my newspaper. Thank you.

[MikeKazlow@adobeforums.com]

Brian,

There are different models for representing color. The RGB (red, green,
blue) model is based upon how different colors of light interact to
make different colors. The CMYK (cyan, magenta, yellow, and black)
model is based upon how pigments combine to create reflected light in
different colors. Most inkjet printers are RGB-based printers even
those that come with cmyk inks. Most CMYK laser toner printers are CMYK
devices. There is no perfect conversion between CMYK and RGB since
there are fundamental differences in the colors they can represent.
Conversion to grey scale is a different issue. If you were only dealing
with one color of red, blue, green, or blue or one of the cyan,
magenta, or yellow using an 8-bits of data for each of the colors, it
would be a simple matter to change from 8-bits of red to 8 bits of
black (i.e, shades of grey). But alas, there is not just one color that
people are dealing with. Different programs and devices use different
methods to do convert from CMYK to RGB, RGB to CMYK, RGB to greyscale
etc. I will have to let someone much more knowledgeable than me to
describe how these conversions are designed.

BTW, It is a good thing, that if you ask Acrobat to convert from CMYK
and the original color space is not CMYK that it leaves it alone.

Mike

[Brian_Hinther@adobeforums.com]

Thanks, Mike. I guess the heart of my question is this: when I need to grayscale a non-device CMYK file, what do I do? Is there a way to make non-device CMYK appear in the "convert from" options so it will work? Or is my only recourse to rasterize it as grayscale in Photoshop (which, of course, I hate to do)?

[MikeKazlow@adobeforums.com]

I have Calibrated RGB and RGB as Devices and I can use them to convert
to greyscale using the greyscale gamma profile. I did this with an rgb
scan with no problem.

Mike

[Doug_Katz@adobeforums.com]

Brian, if you don't mind a momentary thread hijack....

Mike, could you tell me what the term "device" in Device CMYK and Not Device CMYK and Device RGB means exactly?

Thanks.

[Aandi_Inston@adobeforums.com]

> could you tell me what the term "device" in Device CMYK and Not Device CMYK and Device RGB means exactly?

It means "reproduced according to the device".

In the case of CMYK, when you print to a CMYK device (a PostScript
printer, imagesetter, etc.), the amount of C controls cyan ink, the
amount of M controls magenta ink, and so forth.

This is great if the values are right for your printer, imagesetter
etc. If you print to something else, the colors might look
different/wrong.

It is more fashionable to use "tagged color" with ICC profiles. These
say what color recipe was used, and if you use a different device, the
colors are converted: different amounts of cyan, magenta, ... are used
on the actual printer.

Aandi Inston

[Doug_Katz@adobeforums.com]

Ahh. So "device" color "locks in actual values" (sort of?)

And if I, for example, make an illustration for hirez offset in Illustrator or Photoshop, and I Save As PDF with a press quality joboption, the PDF will send to the imagesetter the ICC profile that I've embedded (with the greater flexibility that this implies) or a "device" profile?

Thanks, Aandi.

[Aandi_Inston@adobeforums.com]

"Device" means that there is no profile, so it is in a way the
opposite of locking in color. It locks in color values, which means
the color will vary.

Aandi Inston

[Jon_Bessant@adobeforums.com]

PDF/X-1a requires DEVICE colours since they are indeed locked - this is
a popular choice for many publishers and printers

PDF/X-3 allows for device independent colours - like Aandi states, the
ability to mold to the output device. The PDF/X-3 (and soon to be -
PDF/X-5) specification will be the most popular in years to come since
it supports device modification according to the press environment ...

This will take into account local environmental values such as humidity,
press blankets and press configurations to produce a press sheet which
is *typically* more consistent ..

Jon

[Doug_Katz@adobeforums.com]

Hmm. Well, I won't pretend to understand the fine details you guys are good enough to explain to me (really wish I did) but I get enough to understand that PDF/X-3 and -5 are preferrable if the print house can handle them.

Thank you both.

[Brian_Hinther@adobeforums.com]

If I could hijack this thread back to my intended topic for a moment, let me spell out my problem.

I've gone to Output Preview to check for 4-color black by viewing separations. I turn off the black plate to see if black still remains. It does.

I try to narrow things down with the separations list and discover my file is non-device CMYK. I go to Convert Colors and find my only CMYK choice to convert from is Device CMYK.

I select Device CMYK anyway and tell Acrobat to convert it to Gray Gamma 1.8. It doesn't work.

What can I do differently?

[MikeKazlow@adobeforums.com]

Brian,

Can you post a page of the file?

Mike

[Brian_Hinther@adobeforums.com]

This isn't about a specific file; it's about grayscaling ANY file that is non-device CMYK.

Let me back up. When I go to convert colors, I believe I have only three choices to convert FROM: Device CMYK, Device RGB, and Device (or is it calibrated?) Gray. Should I have more available?

I pick one and then choose a space to convert TO, such as 30% Dot Gain or Gamma 1.8 Gray. Isn't that the way things are supposed to work?

When my file is Device CMYK, the conversion works great. When the file is non-device, the conversion fails.

Isn't there some kind of workaround to grayscale a non-device file?

[MikeKazlow@adobeforums.com]

I don't have any example of a file that is not cmyk, rgb, greyscale, or
BW, that is why I asked for a file that fails.

Mike

[Brian_Hinther@adobeforums.com]

I now have an example of a PDF with some non-device information in it. How do I post it?

[MikeKazlow@adobeforums.com]

Brian,

Post it on a website or ftp site you have access to. There are many places on
the net that offer the service for free.

Mike

[Brian_Hinther@adobeforums.com]

[url]ftp://twinfalls@ftp.lee.net/outgoing/1015.vets.ad.3x10.indd.pdf[/url]

This is a link to our newspaper's ftp site where you can download a PDF that has a small amount of non-device CMYK: the stars and stripes on the medal ribbon behind the photo. Just click on OK in the password box--none is required.

Click on Device CMYK and they disappear. Click on non-device and they appear by themselves. I know it doesn't look like much, but it sure made a mess when it hit our RIP.

I'm sorry this isn't a very good example, but it's the first one since I started this thread. I do get files--generally from Publisher or CorelDraw--where the entire color image disappears when I click on Device CMYK and reappears when non-device is selected. And these are the ones that won't grayscale when I choose Device CMYK to grayscale from, since there isn't a non-device option.

BTW, the ribbon was clip art saved as an Illustrator EPS. Resaving it as an .ai file made it all Device CMYK.

[Aandi_Inston@adobeforums.com]

All the CMYK in that file is DeviceCMYK, without exception. There is
also some marking direct to the black plate.

Aandi Inston

[MikeKazlow@adobeforums.com]

I'm glad Aandi was able to download the file. I get an error mesaage
530 Access denied message.

Mike

[Brian_Hinther@adobeforums.com]

[url]ftp://twinfalls@ftp.lee.net/outgoing/TF_ad1031.pdf[/url]

I don't know how to make this link live, I guess, but here's the path to another file.

This file printed in color (brownish) when I proofed it to our color printer, which tipped me off that it wasn't entirely grayscale.

The file disappears completely when you click Device CMYK and reappears when you click Non Device CMYK, also when you click Gray or Calibrated Gray.

It was the ability to select Calibrated Gray to convert from in the Convert Colors dialog box that allowed me to actually grayscale it (only 100% K). Does this advance our conversation any further?