print shop asks for CMYK, any options?

color
printing
color_management
cmyk

#1

Hi!

I got into this project of printing a calendar with my best photos of the year, and I’m starting to regret it. The complexity of printing your own stuff is way beyond what I first imagined. Grammage (lbs vs gsm anyone?), gloss, opacity, brightness, rolls vs reams, who would have thought printing would get so complicated after Gutenberg? :wink:

I’m pretty advanced in the project, but because I’m having trouble finding paper (yes, you heard that right), I’m considering delegating all this to a print shop again. Unfortunately, they’re asking for CMYK files and from what I can tell, Darktable can only render in RGB (sRGB or Adobe RGB) colorspaces. Is there any way I can accomodate my print shop and provide them with an actual CMYK file?

I know this is like asking to fit a square peg in a round hole, but I figured I might at least open up the discussion so it’s settled: is that something that is (eventually?) feasible in Darktable?

Related:

Thanks!


#2

Krita/Scribus/Sk1 all supports CMYK profiles and color space.


#3

My question is why wouldn’t they accept sRGB, the most common (and variable) profile on earth, and do the conversion for you.


#4

That’s great, but I asked the question here, in the #darktable topic so that I would get information about Darktable, where all my pictures and RAWs and rendering and everything are. :slight_smile:


#5

The thing is Darktable do not support it. I looked it up and it shows imagemagick which is not darktable.


(Mica) #6

Yeah if you want only darktable, you’re out of luck.


#7

gsm is dead easy!
The Imperial way is much more tricky

In order not to hi-jack this thread I will write a longer lamentation
about this abyss in the Lounge…

Have fun!
Claes in Lund, Sweden


(Tobias) #8

If they ask for an CMYK file, change the print shop.


(Andrew) #9

Agree. I’ve never done CMYK.


(Graeme W. Gill) #10

It may just be the way they work, but there are certainly reasons to ship CMYK, if they provide you with a profile for their printing process. (i.e. they don’t have the expertise and just run to generic or industry CMYK ink colors and TVI curves, or don’t wish to take the responsibility of doing the conversion.)

Primary advantages are:

  • You can check and adjust your images to look their best within the CMYK color gamut.
  • You can make text be black only, to avoid registration issues.

Of course these sorts of things are a bit technical for casual users…


#11

There is an update for the little Cyan application. https://cyan.fxarena.net/

Read the blurb or a little demo here: https://youtu.be/1A0Aaoy1mhQ

Use it stand-alone or it will install its own plugin into Gimp as a link.

Tried it out in linux (kubuntu 16.04), Win10 (VM) and Gimp 2.10.8 Maybe still a little flaky but it is small-ish and not many (any) replacements for separate+ out there.


#12

So what I hear from everyone is basically: “no, Darktable doesn’t support CMYK output or conversion”. That I already knew: I can browse through menus and search online. As I mentioned in the original post, there is already a discussion on the topic in this very forum where a DT dev clearly outlines that points are stored in 3-value pairs and do not map directly to the 4-values CMYK requires.

(Incidentally, I’ve also heard comments about how print shops should all stop using CMYK and switch to sRGB which I find rather short-sighted and far from reality. Print shops have existed for centuries I find it hilarious that computer geeks think they can give meaningful advice to those folks. Beyond that, sRGB’s color space is remarkable small compared to CMYK or (even) Adobe RGB so it seems to me that accepting sRGB would sure be nice, but forcing them to convert their workflow to that limited color space would be unproductive.)

So that’s not exactly what I was looking for. :slight_smile: My question is more whether this could eventually be supported in Darktable. From what I can tell, there’s very little interest in doing so, but I nevertheless think it might be an interesting feature, given that DT already has extensive color space and calibration support. Isn’t this, after all, just another calibration?

As for my specific problem with that print shop, yes, switching is an option, but I might also hack my way around the problem with LaTeX, which I’m already using to edit the whole thing…

I have also heard (elsewhere) suggestions to use GIMP to perform the conversion (and also Krita and ImageMagick here of course), but I’d rather avoid adding another step in my already complex workflow. :slight_smile:

Thanks for all the feedback!


#13

Actually Adobe RGB has higher gamut than CMYK. Some samples here. The visible sample would be LCH/LAB I guess…


(Tobias) #14

OK, more text this time. I said you should switch the print shop not because a CMYK workflow is bad, but because asking a customer to provide CMYK images is not fair. The problem is, now you have to do the job of the print shop. You can’t just convert an sRGB image to CMYK (Yes you can but the results are not optimal.) You need an ICC Profile from the printer and the paper, an calibrated monitor and you need to know how the colour the colourpicker shows will look printed. That’s because the monitor can’t show all colours you are able to print. And that’s the think you can’t and why it is not fair.

Beyond that, sRGB’s color space is remarkable small compared to CMYK or (even) Adobe RGB so it seems to me that accepting sRGB would sure be nice, but forcing them to convert their workflow to that limited color space would be unproductive.

CMYK is a colour model and not a colour space. You must compare CMYK with RGB and not with a colourspace like sRGB. Have a look at this nice image I found with colour spaces from different printers:

So that’s not exactly what I was looking for. :slight_smile: My question is more whether this could eventually be supported in Darktable.

This depends on what you expect. It would be quit simple to write a dt Lua script that converts a RGB Tiff file during the export to an CMYK Tiff file and adds an CMYK ICC profile. This would help everyone who needs to send an image to a print shop that ask for CMYK. But I don’t thin it would help to make better prints. Would you be happy with such a solution?


#15

For those who want to dive deeper:

http://www.printernational.org/

Have fun!
Claes in Lund, Sweden


#16

Awesome, that’s more like it. :slight_smile:

Yeah, I figured CMYK was “kind of like RGB but not sRGB or Adobe RGB”… And of course you’re right CMYK does not necessarily have a larger gamut than sRGB but I figured that a good print shop actually will have a printer with a larger gamut than sRGB. :slight_smile: Maybe that’s where I got my assertions wrong, as @Reptorian pointed out…

Honestly, I would expect this to be part of the “Export selection” dialog. Right now I see this:

Screenshot of Darktable 2.4.4 export selection tab with profile dropdown expanded

It seems to me there should be room for custom profiles in there, including support for CMYK output profiles.

My rationale is I am a DIY kind of guy and I like to explore. And I hold Darktable to the highest standards, because it’s been doing that so well elsewhere. :wink: That means I expect to be able to deal with high-end printers out there.

But as others have told me, modern printers do not care much about CMYK vs RGB these days: as long as you have the right ICC profile applied so you can see the result, it can do the conversion for you in the back.

That is, if I understand the problem space (no pun intended) correctly, which I have been extremely bad at historically. :wink:

Thanks again


#17

Not that I want to complicate matters even more, but … … …
Some printers do not print in CMYK – they print in MYCK!

Have fun!
Claes in Lund, Sweden


(Roman Lebedev) #18

There’s endianness joke in there somewhere.


#19

Yes, but would it be a big- or little-endian one?


#20

That was a rather pointed response. I know that this could be a frustrating learning process. I suppose that adding more CMYK tools wouldn’t hurt. But I can understand why CMYK isn’t dt’s priority. Let me clarify.

@gwgill’s remark leads to my point. Shops should give customers options and work with them to provide the “best” result. Simply asking customers to convert to CMYK won’t produce great prints. It isn’t an either or problem (sRGB or Adobe RGB vs CMYK).

Except it does matter. It isn’t just about providing the correct profile. It is also about being able to do the converting with the printing workflow in mind; keeping colour management intact from creation to consumption; and making sure that the print job satisfies the customer’s expectations.

Inevitably, the results would be different from the moment of creation (whether by camera or computer) because the media and viewing conditions are different, physically and aesthetically. The key is to embrace the new format (print) while respecting the workflow (optical or display).

An analogy to this would be the process of adapting a TV show, movie, comic or stage play from a book. Although the ideas would be the same, the results would be vastly different for better or for worse.