How to Grayscale a non-device CMYK file

[Aandi_Inston@adobeforums.com]

Ok, here's the story on this file.

There is indeed no DeviceCMYK.

The entire file (one image) is created using DeviceGray instead. Now,
this is where things get complicated. The file includes a default
greyscale profile.

Some tools honour the default profile, and do a profile-to-profile
conversion. Other tools may not, using the DeviceGray as a greyscale
value (or K ink value) directly.

The embedded profile is the "20% dot gain" profile, probably put there
because of a choice to use color management in Photoshop's PDF export.

Aandi Inston

[Brian_Hinther@adobeforums.com]

Thanks for taking a look, Aandi.

So you're saying the non-device CMYK values (4-color black) got there through color (mis-)management?

[Aandi_Inston@adobeforums.com]

There's nothing wrong with DeviceGray: I'd hope a greyscale image was
stored with DeviceGray rather than using up excess space for blank
M,Y,K channels.

The problem may be color management. Often people who make files see a
"color management" box and tick it assuming that's a good thing...
then complain that colours change. On the other hand, maybe Photoshop
does it unconditionally, I haven't tested it.

Aandi Inston

[John_Slate@adobeforums.com]

Brian:

As wrong as this sounds, uncheck "preserve black", select "don't include profile", and set to gamma 1.8 or 2.2

[pjonesCET@adobeforums.com]

use 2.2 if items are to be sent to PC people and 1.8 if to be sent to Mac people.

[Brian_Hinther@adobeforums.com]

John and pjones,

Thanks for the tips.