PDF Plotter "True" Greyscale (CMYK 0/0/0/x)

[Anonymous]

Hi everyone,

I'd like to plot the index color 253 to PDF as a true greyscale, meaning that in the PDF file the grey should have CMYK values like 0/0/0/25 (just an example value).

Because I have also Adobe software installed on my computer I have the additional plotter "Adobe PDF" besides the standard AutoCAD PDF plotters.

If I use the Adobe PDF plotter I get a "true" greyscale. If I use one of the AutoCAD PDF plotters the grey still looks the same, but has CMYK values like 13/25/18/8 (example value!)

How can I get the correct CMYK values with the AutoCAD plotter? Because I have to use that one...

I think the reason for the difference is in the plotter settings for the vector graphics. But I don't find a way to change that...

[pendean]

AutoCAD does not do CMYK. So there is that major hurdle.
Do you use a plot style table in AutoCAD? If yes, is it CTB or STB?
Why use color 253 at all, is there a similar RGB or HSL inside AutoCAD that would get you the same effect?

Or use a COLORBOOK, see this tip from another post https://forums.autodesk.com/t5/autocad-forum/cmyk-color-settings-in-autocad/m-p/8007084#M933583

[Anonymous]

I know that Autocad can't do CMYK. And that's not what I directly want (in other words: I don't want to set a CMYK color directly in Autocad.)

For my tasks in Autocad I use a ctb plot style table. But for my tests I've tried the greyscale table as well as plotting without plot style table. In both cases I've got the explained results...

Color 253 is just an example because we have been using this one for several years now for grey lines in article drawings for our sales manual.  I'd like to know why the grey color in the pdf gets different color values depending on the plotter...and how I can correct that for the AutoCAD PDF plotters.

Background: The mentioned article drawings are on pages which only get printed with just two plates: Black and green Pantone. That's why the grey color in the article drawings mustn't contain any CMY values.

Another thing: In our old Autocad version (2006) we were plotting to eps-files. Back then the same color in Autocad (253) was converted to a correct grey in the eps file!

(I could convert the pdfs afterwards, but I don't want this, because I would have to do this everytime again.)

I will have a look on the linked topic...but not sure at the moments, if that helps

[pendean]

So why did you ask about CMYK if you knew all along? I'm curious really, not argumentative.

You posted screenshots of your PC3 files in your first post , if you want to edit what colors your CTB file use, you need to open your CTB files to do so: for example, start STYLESMANAGER command, double-click on the CTB to edit, go to the FROM VIEW tab, click on color 253, use the COLOR pulldown to select OTHER, then either come up with an RBG/HLS alternative or do the COLORBOOK option in the link I posted earlier https://forums.autodesk.com/t5/autocad-forum/cmyk-color-settings-in-autocad/m-p/8007084#M933583

HTH

[leeminardi]

Is it worth a try to test the Microsoft Print to PDF option?  It's 32 bits may support the extra 8 bits for K that you need for compatibility.

[Anonymous]

@leeminardiI don't have this one.

@pendeanMaybe I still didn't clearly explained my problem. So I try the follwing example.

Let's say I want a grey object, which has to be printed in CMYK 0/0/0/50. That colour would correspond with RGB 128/128/128 (more or less) which correspond with index color 8 in Autodesk.

So I create my object and assign index color 8. For testing purposes I select "none" for the plot style table*. Now choosing the Autodesk PDF plotter this grey has in the PDF file the CMYK values 49/38/39/20. Choosing the Adobe PDF plotter with the exact same settings the grey has the needed and correct CMYK value 0/0/0/50.

These different results are my problem. I need the correct CMYK outcome while using the Autodesk PDF plotter.

* Even if I set up the the correct corresponding RGB/HCL values for 0/0/0/50 CMYK in a plot style table (because I can't directly set up a CMYK value - which I already knew) the outcome is the same. The Autodesk PDF plotter creates a PDF with a "colored grey" (49/38/39/20).

[Anonymous]

@leeminardi  I dont' have this one.

@pendean  Maybe I didn't clearly explained my problem. So I try the following example.

Let's say I want a PDF with a grey colored object and this grey should be printed with CMYK values 0/0/0/50. That corresponds (more or less) with RGB 50/50/50 which corresponds with AutoCADs index color 8.

So I start a new drawing, create the object and assign index color 8. Now I plot* this one with the Autodesk PDF Plotter. The result is that the grey has CMYK values of 49/38/39/20. Now I plot the exact same object with the exact same settings with the Adobe PDF plotter and I get the correct CMYK value: 0/0/0/50. This different outcome is my problem. I want the correct CMYK value while using the Autodesk PDF plotter.

* For testing purposes I choose "none" for the plot style table. Even if I set up one with the correct corresponding RGB/HCL values - because I can't directly set up a CMYK color (which I already knew) - I get the same result: a "colored grey".

[pendean]

OK, thanks.

No fix inside AutoCAD or the PC3 file except possibly as the workarounds already mentioned (or you only use the one driver that suits your CMYK output needs best).

[leeminardi]

Try this link to get the 32 bit  Microsoft Print to PDF option.

[AdammReilly]

How are your grayscales defined? Are they using an actual RGB color to define the gray? (The Grayscale.ctb does this) Or do you use the screening values in the ctb file? 

Because Autocad is an RGB based system, some greys will be represented with a RGB value, which could cause some color variance depending on the output (some pdf's may show weird coloring in hatches, also dependent on other settings in the pdf viewer; plotters may plot the grays as different hues). But, if you are using the screening values, you would set the color to Black and have it reduce the value to a percentage of black. Of course, this relies on whether the output device has that capability (most modern devices do).

[Anonymous]

The greyscales are defined by RGB. (so far we have always used the AutoCAD index colors for different grey colors) But I've just tested your way using the screening value in the ctb:

Created a black object and defined a screening value of 55 in the plot style table.

Adobe PDF as plotter: Acrobat shows a CMYK of 0/0/0/55 -> correct

AutoCAD PDF as plotter: Acrobat shows a CMYK of 53/43/42/25 -> wrong

Is it really just me or does the AutoCAD PDF plotter simply not suppport "true greyscale"? And I really hoped after updating from AutoCAD 2006 and seeing the standard installed AutoCAD PDF plotters my work would become easier.

@leeminardiSeems like this is only available in Win 10. At the moment I'm still using Win 7.