Acrobat color conversion: DeviceGray vs DeviceN "Black" CMYK (0, 0, 0, 1)
Acrobat color conversion: DeviceGray vs DeviceN "Black" CMYK (0, 0, 0, 1)
- Subject: Acrobat color conversion: DeviceGray vs DeviceN "Black" CMYK (0, 0, 0, 1)
- From: "Jorge ." <email@hidden>
- Date: Tue, 20 Dec 2016 11:21:09 +0100
When exporting to PDF with InDesign CC 2015.4 using the default PDF/X-4
preset, grayscale images filled with the default solid Black swatch (100K,
Uncoated FOGRA29) are exported as DeviceGray, unless somewhere in the
layout there also exist a partially transparency vector object using the
same black, in which case those grayscale images are exported as filled
with DeviceN: "Black" CMYK (0,0,0,1) instead.
Is there a way to control this, or a reason for it? Is there any way, with
Acrobat or a free command-line tool, to replace the DeviceN: "Black" CMYK
(0,0,0,1) black of grayscale images with DeviceGray?
Why do I care:
When using Acrobat DC 2015 to convert all colors to sRGB (Tools > Print
Production > Convert Colors > Convert colors to output intent: sRGB),
Acrobat maps the black of vector objects filled with the default solid
black (100K) to black RGB (0,0,0), and does the same with the black of
DeviceGray grayscale images. All blacks in those PDFs consistently become
0,0,0 RGB.
But if grayscale images were exported as filled with DeviceN: "Black" CMYK
(0,0,0,1), their black is converted to RGB muddy gray, and therefore color
conversions of layouts containing both vector objects and grayscale images,
both filled with solid black, produces inconsistent RGB blacks.
Just to clear up: my purpose is not obtaining color-accurate RGB
conversions of CMYK solid blacks, but getting RGB blacks that are pleasant
for screen viewing, i.e. 0,0,0 RGB. That, I already get from 100K-filled
vector objects when converting colors as described above, but not from
grayscale images filled with DeviceN: "Black" CMYK (0,0,0,1). I do
understand CMYK solid blacks do not match in fact their color space's black
point, and therefore that a color-accurate conversion should produce RGB
muddy grays, and I can indeed also get Acrobat to do that for all 100K, be
them from vector objects and from grayscale images filled with DeviceN:
"Black" CMYK (0,0,0,1), by using Acrobat's "Conversion Attributes" color
conversion options instead of "Convert Colors To Output Intent". But what I
want them to be is consitent 0,0,0 RGB.
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