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K only button in AD desktop missing

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1 hour ago, Lagarto said:

You need to have the document in CMYK mode to have the K-only button

Oddly enough, if you have set a linked image to K-only and copy it into an RGB document, it will retain the K property with no way to change it directly, except for clicking Replace Image to reload it in color.

Interesting feature otherwise. Haven't even noticed it yet.

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5 hours ago, Lagarto said:

you cannot toggle K-Only for an RGB image, at least on Big Sur 11.1, on an M1 chip

Works for me, El Capitan on MBP 2012.
Make sure it's a placed image and not converted to a pixel layer.

5 hours ago, Lagarto said:

for true grayscales, K-Only is by default turned on (meaning that the image behaves normally), but if you turn it off, the image is handled as an RGB-gray image!

That makes sense, to me at least.

5 hours ago, Lagarto said:

a handy feature (especially for coloring images)

Yep. This thread inspired me to this post:

5 hours ago, Lagarto said:

you want to have full control on what happens to actual color values

If I want to have full control, I will always, always convert an image in a bitmap editor of choice before importing. I.e. previously in Photoshop, these days more and more often APh while I'm beginning to understand how it works, and from time to time only double-checking the result in Photoshop – as long as it works on El Capitan – if all is as expected.

And then double-checking the exported PDF/X in Acrobat for separations.
(Still no idea what to use if I eventually move on to Catalina. I guess I'll build me a Ghostscript workflow, as suggested in another thread here just recently.)

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Diving further into it to understand "K only", let's sum up this way:

  • If you place a CMYK image, it will disable CMY. Seems logical to me, as in: "it does exactly what it says it does".
  • If you place a Grayscale image, "K only" is on by default. That's definitely a Good Thing™ as far as I'm concerned!
    But you can turn it off and then it becomes a composite image. That again means that you can apply color adjustments like Curves or Color Balance to colorize it in a way that's not possible on a K-only grayscale image. That's a Good Thing™, too!
  • If you place an RGB image, there's literally no "K" to turn on or off, so it has to do a conversion. The question is: How? Comparing an RGB image turned gray via "K only" and via adjustment layer Black & White "30/89/59/70/11/41", the result was the same. So that's a Good Thing™ as well.

Here some examples what happens in APu with RGB, grayscale and CMYK version of the same image which I've once used in a "real life" layout – done in Illustrator CS5 then – a few years ago:


^ Frankly, I like what I see. From what I recall, I was struggling a bit to figure out how to handle this in Illustrator to achieve this "washed out bad print" effect (screenshot from the final PDF/X-3):


(On the other hand, I'm not sure yet if APu could handle all my "fake overprint" effects the way that Illustrator does. To be investigated another time… ;))

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The hard part is that you can't save adjustment presets in APu, thus for Black & White you'll have to learn the "30/89/59/70/11/41" mantra by heart.
Alright, actually just 30/59/11, the rest is simple math.
And 30+59+11=100

But still, it took me at least 5 years to learn my cell phone number by heart. And only in Czech…

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On 2/11/2021 at 11:16 AM, loukash said:

(Still no idea what to use if I eventually move on to Catalina. I guess I'll build me a Ghostscript workflow, as suggested in another thread here just recently.)

Ghostscript separations work, featuring the "K Only" button in action:


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  • 7 months later...

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