Re: Colorsync-users Digest, Vol 13, Issue 169
Re: Colorsync-users Digest, Vol 13, Issue 169
- Subject: Re: Colorsync-users Digest, Vol 13, Issue 169
- From: "Jorge ." <email@hidden>
- Date: Wed, 21 Dec 2016 17:29:12 +0100
Thank you for your ideas.
Exporting from InDesign straight to sRGB does convert both 100K and
black in grayscale images to RGB 0,0,0, but my intention was batch
converting PDFs already exported PDF/X-4. Having to go back to the
original document and depending again on InDesign is far less flexible
than I would like it to be.
I did try Callas pdfToolbox, but either I did not know how to or it
cannot accomplish what I wanted (replace only the DeviceN: "Black"
CMYK (0,0,0,1) fill in grayscale images with DeviceGray 100% black).
How to accomplish that, though, was only part of my question. I was
wondering several whys?
- What is the reason, if there is one, why InDesign might need to
export grayscale blacks sometimes as one thing and sometimes as the
other when exporting to PDF/X-4?
- Is there any way to control that?
- What is the reason, if there is one, why Acrobat, when using
"Convert Colors To Output Intent" on such PDFs, converts 100K in
vector objects and 100% black in DeviceGray images to RGB 0,0,0, but
black in images filled with DeviceN: "Black" CMYK (0,0,0,1) to a
different value, non-neutral and non-100% black .
Best regards.
On Wed, Dec 21, 2016 at 7:41 AM, Péter Nagy <email@hidden> wrote:
>
> Hi Jorge,
> the problem you described is a problem for many people. Without high-end tools your first choice is to do a group of trial-and-error experiments, using all the options in your version of Acrobat. I assume you've done that already. If you can access the original material (the InDesign doc and all the linked images), you can try exporting directly to sRGB.
> If your input is strictly PDF, then the last resort is a professional tool like Callas pdfToolbox. Using that software you have access to sophiscticated (albeit circumvent) ways to map any kind of black to K. They have a free 14 days trial for first time downloads so you can play around with the options until you find a solution.
>
> Kind regards,
>
> Péter Nagy
> Colorcom Media, Budapest
>
>
> > Date: Tue, 20 Dec 2016 11:30:33 +0100
> > From: "Jorge ."
> >
> > Here is a set of files illustrating the issue: https://cl.ly/1a1v0m0v2127
> >
> > • `image.tif` is a 100% black grayscale image.
> >
> > • `DeviceGray.indd` is an InDesign document (idml also provided) containing
> > the image plus an opaque vector object filled with the default 100K Black.
> > Exporting using the preset PDF/X-4 generates `DeviceGray.pdf` which uses
> > DeviceGray for the grayscale image.
> >
> > • `DeviceN.indd` is an identical InDesign document except for the fact that
> > the vector object is given partial transparency. Exporting using the same
> > PDF preset generates `DeviceN.pdf` which uses DeviceN: "Black" CMYK
> > (0,0,0,1) for the grayscale image instead of DeviceGray.
> >
> > Using Acrobat to convert colors to sRGB (Tools > Print Production > Convert
> > Colors > Convert colors to output intent: sRGB) provides consisted RGB
> > 0,0,0 blacks for both the vector object and the grayscale image in
> > `DeviceGray.pdf` but not in `DeviceN.pdf`.
> >
> > On Tue, Dec 20, 2016 at 11:21 AM, Jorge . <email@hidden>
> > wrote:
> >
> > > 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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