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LogosByDim

What's the difference between choosing "Assign" or "Convert" when changing color space from RGB to CMYK?

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5 minutes ago, LogosByDim said:

Upvote. Someone got an idea? The CMYK profiles are not few, as you all know.

Common sense says use profiles your customer is going to use. You have to ask to what uses customer is going to put your design: letterhead, packaging cardboard, newspaper print etc... and probably supply a version for all those uses. The logo should look the same in all uses, or you have design a simplified version for lower quality printing methods.

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17 minutes ago, Chris26 said:

My obvious question mark banging up and down on the top of my nicely brushed and radiant hair as I read this was:  Exactly which of the myriad of cmyk profiles should one adopt when setting up one's document?  

I've asked this too, and on other threads.. People talk of CMYK like it's a defined thing, but it's not an absolute space like CIE lab/xyz. Unless you know when starting a design which print profile it will use it's going to be easy to select a profile that's actually smaller than the capabilities of the press. Affinity defaults to SWOP coated which is very limited.

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5 minutes ago, Fixx said:

Common sense says use profiles your customer is going to use. You have to ask to what uses customer is going to put your design: letterhead, packaging cardboard, newspaper print etc... and probably supply a version for all those uses. The logo should look the same in all uses, or you have design a simplified version for lower quality printing methods.

Obviously, may I clarify what I should have asked - One often designs and does not have a printer in mind, maybe one is not necessarily designing for a client, as of yet.  What then becomes the most appropriate CMYK profile to base all your work on?  Hence, the need to do all in RGB, or am I wrong on this point?


Microsoft - Like entering your home and opening the stainless steel kitchen door, with a Popup: 'Do you really want to open this door'? Then looking for the dishwasher and finding it stored in the living room where you have to download a water supply from the app store, then you have to buy microsoft compliant soap, remove the carpet only to be told that it is glued to the floor.. Don't forget to make multiple copies of your front door key and post them to all who demand access to all the doors inside your home including the windows and outside shed.

Apple - Like entering your home and opening the oak framed Kitchen door and finding the dishwasher right in front you ready to be switched on, soap supplied, and water that comes through a water softener.  Ah the front door key is yours and it only needs to open the front door.

 

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2 minutes ago, BofG said:

Affinity defaults to SWOP coated which is very limited.

Just a question. Does that mean that using the default SWOP, CMYK profile would be a pretty safe profile to use in regards to a printing shop requirement?

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3 minutes ago, Chris26 said:

Obviously, may I clarify what I should have asked - One often designs and does not have a printer in mind, maybe one is not necessarily designing for a client, as of yet.  What then becomes the most appropriate CMYK profile to base all your work on?  Hence, the need to do all in RGB, or am I wrong on this point?

Here in cold and desolate northern Europe it would be quite safe to use Fogra39 for general print jobs. Often RGB version is appropriate too.

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22 minutes ago, Fixx said:

Here in cold and desolate northern Europe

Fixx, would that mean we should use the CMYK profile that is commonly used in a specific area, like Europe or the US?

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1 hour ago, LogosByDim said:

Just a question. Does that mean that using the default SWOP, CMYK profile would be a pretty safe profile to use in regards to a printing shop requirement?

Not necessarily so. As it has been said it depends on either (most) common usage in a certain area of the world or what the printer who's gonna do the print job for you expressively asks for. There are very likely to exist established or standardised workflows in regard to specific print processes (sheet offset, roll/continous offset, newspaper print or whatever). You should possibly ask your printer(s) for information about the standards they adhere to.

I personally mostly use the ISOcoated_v2 colour profile for CMYK being the one that's most commonly used by printers around here. Or ISOcoated_v2_300 which is basically the same but limits ink coverage to a maximum of 300% which is preferred by some of the bigger online print services as printed sheets dry faster when there is less ink coverage.

That said, one should remember that regardless of the profile you have initially set for your (layout) document (even if that should preferably be the most common one in your area) it is actually the job of an application's internal colour management to create the final PDF for printing according to the profile you haven chosen in your output/export settings! You may have initially created our design for usage in regular sheet offset printing, but when your client then needs another PDF to be sent out to be printed on sort of "spongy" newspaper stock you will most certainly have to export your design using a CMYK profile which separates the colours accordingly (i.e. most likely with considerably less ink coverage). That's what Colour Management has been meant for in the first place.

Mind, however, that all this predominantly applies to outputting final printing PDFs from a layout application like Affinity Publisher or Adobe InDesign!

Colours of CMYK vector objects should – in my opinion – be preserved anyway 1:1 by the layout application they are placed or copied into, because it generally seems to be a sound assumption that the colour values defined in CMYK for these objects are actually meant to be precisely as they are (e.g. in logos etc.).
On the other hand photos – and generally photo-like "pictures" – can or should be left as they are (assuming they have an assigned colour profile that's saved inside of them and that is detectable by – say – Affinity Publisher) – for purposes of correctly display on screen the layout app should be able to convert the colours according to the profile chosen for itself (the layout document). For purposes of creating a PDF for printing the export settings should take care of that.

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2 hours ago, BofG said:

People talk of CMYK like it's a defined thing, but it's not an absolute space like CIE lab/xyz.

 

44 minutes ago, Lorox said:

Colours of CMYK vector objects should – in my opinion – be preserved anyway 1:1 by the layout application they are placed or copied into, because it generally seems to be a sound assumption that the colour values defined in CMYK for these objects are actually meant to be precisely as they are

This is where I have to disagree :)

CMYK is not a fixed thing, you need a profile to map those values into the "real world" as it were. CMYK values without a profile are not anchored to anything. Keeping them "1:1" isn't possible, you either have to convert them or strip the current profile from them and assign the new one.

You can have "DeviceCMYK" in a PDF, which are taken "as is" by the press, but these are a final step in the colour management, they are produced by the upstream icc profile(s).

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14 minutes ago, BofG said:

CMYK values without a profile are not anchored to anything. Keeping them "1:1" isn't possible, you either have to convert them or strip the current profile from them and assign the new one.

I'm not quite sure how this is handled in the Affinity apps but I've worked in InDesign for a long time and in InDesign's colour management settings you could/can set the rule that CMYK content preserves/keeps its "numbers" (meaning its original CMYK values) when placed/pasted into the layout document.

This actually makes a lot of sense to me as this way I could/can be sure a logo's colours defined for print with certain CMYK values in fact "migrate" 1:1 from the original – say – Illustrator logo design document to the layout document (and on to the PDF for printing). This way these colours are treated exactly the same way as if they had been just assigned within – say – InDesign using its current colour profile. Accordingly they don't get changed when in exporting the PDF for printing that very colour profile is used. So the logo's CMYK colour values will be exactly the same in the PDF for printing as they have been in the original CMYK AI design file (which is what you generally want).

As I said I'm unfortunately not eactly sure how this really works in Affinity Publisher and Designer... (I definitely wish I knew exactly – I'd feel quite a bit more relaxed when giving PDFs away now that I'm trying to adopt the Affinity apps as my premier go-to design apps...)

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As far as I'm aware, there's no way to work with unmanaged colours in Affinity. If you are going from one cmyk colour space to another you have to either convert (ie. Map back to the Profile Connection Space then forward to the new profile) or assign (ie. Use the "raw" numbers with the new profile). I don't know how InDesign handles it. There is always the possibility that the two profiles are so similar you wouldn't actually notice. I can't imagine though that it would be truly non colour managed. Although I have been known to be wrong :)

My point was the "CMYK values" are not a guaranteed "colour". It's like saying a client's logo is a "purple-ish blue", saying "C:100 M:80 Y:0 K:0" is no different - they are both open to interpretation. If you say it's "C:100 M:80 Y:0 K:0 in SWOP coated" then you are talking about a specific colour. The profile anchors the colour values to a real world output that is defined and consistent. If you then wanted that colour on some ivory stock you would be printing quite different values for the same final colour.

It could be that InDesign is keeping the same colour values in your document by setting the pdf output intent to the assigned profile, but is not using that itself when you read the file back in.

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9 minutes ago, BofG said:

... I don't know how InDesign handles it...

ID is (depending on settings as mentioned) color agnostic. QXP is fully color agnostic (and only color agnostic). Any/all color conversions happen at output. Which is what APub/AD out to have been made as. But that is now water under the bridge.

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24 minutes ago, MikeW said:

ID is (depending on settings as mentioned) color agnostic. QXP is fully color agnostic (and only color agnostic). Any/all color conversions happen at output. Which is what APub/AD out to have been made as. But that is now water under the bridge.

That's interesting, do you know how it's done technically? To apply a profile on output would require the colours to be in CIE Lab/xyz, I wonder if the documents are working in that space behind the scenes, or is it some other approach?

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Via the "Profile Connection Space (PCS)" which it is either LAB or XYZ.
 

Quote

 

The conversion of an RGB image to CMYK might then look like this, for example: RGB: 200/150/0 > LAB: 65|25|83 > CMYK: 2/45/100/11. But ...

However, this representation is misleading because it gives the impression that when converting the image is first converted to LAB and in the second step from LAB to the target profile. In fact, the source and target profiles are linked directly to one another before the conversion. Thus, for the time being, only one translation table (link table) is created which, taking into account various parameters (such as rendering intent, depth compensation, etc.), connects the corresponding tables (A2B of the source profile and B2A of the target profile) using the Profile Connection Space. This creates a temporary “DeviceLink profile” which converts the image pixels directly from the source to the target profile. This means that the actual image information, i.e. the pixels, is never in the PCS. LAB or XYZ is therefore not an intermediate step when converting the images, but only one when linking the two profiles or the two tables.

Of course, this approach works fine if there are two tables to be linked. This means that it always works when there are two LUT profiles. But what if the transformation is a pair of a matrix and a LUT profile? Then a suitable table is first generated from the matrix profile and this is then linked to the table of the LUT profile that is already available. But even when converting between two matrix profiles, the two matrices involved are linked directly to one another and not all image information is first transferred to XYZ.

The advantage of this method, i.e. the creation of such a latent translation table is that rounding errors cannot occur twice. In addition, the tables are always calculated with 20-bit accuracy, regardless of whether the image material is available in 8 or 16 bits. Incidentally, this is a special feature of Photoshop and is not defined in the ICC specifications. You could also say Photoshop exceeds the specifications of the ICC. It was Thomas Knoll himself who made this change because he wanted to achieve higher conversion accuracy. Thomas Knoll was not only (together with his brother) the inventor of Photoshop but also the lead developer of the Adobe Color Engine (ACE).

 

See also ...


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There's so much interesting information going on here and I wonder how we got so deep into technical details from a single question about color profile conversion and assigning. I hope many will find this topic helpful when it comes to a lot things related to colors in the Affinity apps and more.

Thanks to everyone for contributing with opinions and answers!

 

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I find it an interesting topic, it's also interesting how many different viewpoints there are on things. There's also a lot of misconceptions, it's a bit of a minefield! :)

The way the applications handle colours can add to the confustion, take the following example:

1) Create an sRGB document.

2) Export to PDF X-4 with default settings:

x4-settings.png.e4e68b1e780b312e11e298ae1c31ed08.png

- Clearly the colour space will be sRGB right? Well....

3) Open the document in Adobe Reader, click the "standards" icon:

standards.png.8e34c337365fd1c34972b840b9b21c66.png

YEP! That's good old SWOP v2 in your output intent - which Adobe Reader certainly honours. Why???!??!? RGB colour spaces are supported in X4 pdf files, so who only knows why Designer does this.

On top of that, when actually trying to print, you've then got colour management at the OS level, the application level and the driver level. All of which are quite happy to be set in conflicting ways. Colour management is a very fractured setup. I'm still enjoying learning about it though, and discussions on here have helped my understanding so thanks all for participating.

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19 hours ago, Chris26 said:

My obvious question mark banging up and down on the top of my nicely brushed and radiant hair as I read this was:  Exactly which of the myriad of cmyk profiles should one adopt when setting up one's document?   Should have added, assuming one is designing something but has no idea which priter one might be sending it to.

You can read up on what profiles are used and how and where to deploy them here:

http://colormanagement.org/index_en.html
This is where I get all my profiles from, but having said that a lot of printers make their own or have them made from a fingerprint of their machine using a calibration sheet or the IT8 method, so it´s always best to consult with your friendly neighborhood printer first.

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5 minutes ago, Slammer said:

This is where I get all my profiles from, but having said that a lot of printers make their own or have them made from a fingerprint of their machine.

Hi Slammer, well thankyou.  I vaguely remember this website from years and years ago but had completely forgotten it, so I am actually thankful you took the time to give me the link.


Microsoft - Like entering your home and opening the stainless steel kitchen door, with a Popup: 'Do you really want to open this door'? Then looking for the dishwasher and finding it stored in the living room where you have to download a water supply from the app store, then you have to buy microsoft compliant soap, remove the carpet only to be told that it is glued to the floor.. Don't forget to make multiple copies of your front door key and post them to all who demand access to all the doors inside your home including the windows and outside shed.

Apple - Like entering your home and opening the oak framed Kitchen door and finding the dishwasher right in front you ready to be switched on, soap supplied, and water that comes through a water softener.  Ah the front door key is yours and it only needs to open the front door.

 

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1 hour ago, BofG said:

...YEP! That's good old SWOP v2 in your output intent - which Adobe Reader certainly honours. Why???!??!? RGB colour spaces are supported in X4 pdf files, so who only knows why Designer does this. ..

Quote

A PDF/X-4 file always contains a CMYK ICC profile that defines the CMYK color space of the intended output device. This profile must be used to convert all CIE based objects in the PDF (Lab, RGB with attached ICC profile, CMYK and Gray with attached ICC profile) to CMYK.

RGB objects having an attached ICC profile have to be converted from RGB to CMYK using the RGB ICC profile and the CMYK output intend profile. Note: PDF/X-4 forbids the use of RGB objects without attached ICC profile (DeviceRGB).

CMYK  objects  having  an  attached  ICC  profile  have  to  beconverted from source CMYK to output intent CMYK using the attached CMYK ICC profile andthe CMYK output intent profile. Gray objects having an attached ICC profile have to be converted from source Gray to output intent CMYK using the attached CMYK Gray profile and the CMYK output intent profile.
 Note:  PDF/X-4 forbids the use of CMYK objects with an attached ICC profile that is identical to the output intent profile to avoid unwanted color conversions that can negatively impact separations. Note:  PDF/X-4 allows use of untagged gray objects (DeviceGray). In this case gray is mappedon the black channel of the CMYK output space.

...

...though I would have expected an ISO CMYK profile for european localized users.


☛ Affinity Designer 1.8.3 ◆ Affinity Photo 1.8.3 ◆ OSX El Capitan

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24 minutes ago, v_kyr said:

though I would have expected an ISO CMYK profile for european localized users.

Yep, this is what I mean about the software obscuring things. That profile isn't refered to at all in the output settings, I see now why it's in the document but it's very obscure and is selected by the program in an opaque manner.

It then begs the question, what colour model is being used internally? Would it be ICC tagged RGB? I don't have the tools to see the internal setup of the pdf unfortunately.

The more I learn the less I understand :)

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13 minutes ago, BofG said:

Yep, this is what I mean about the software obscuring things. That profile isn't refered to at all in the output settings, I see now why it's in the document but it's very obscure and is selected by the program in an opaque manner.

It then begs the question, what colour model is being used internally? Would it be ICC tagged RGB? I don't have the tools to see the internal setup of the pdf unfortunately.

The more I learn the less I understand :)

Welcome to the club... I think the best practice is to ignore profiles or set up generic profiles until you go to PDF.

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It's a shame that the pdf output is so badly presented. I've read the specs (although clearly not the "x" type standards) and there's some very fine grained colour control available, yet the export options either give no control or just default to questionable settings.

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3 hours ago, BofG said:

YEP! That's good old SWOP v2 in your output intent - which Adobe Reader certainly honours. Why???!??!? RGB colour spaces are supported in X4 pdf files, so who only knows why Designer does this.

Interesting thing you've got there.
I think the these PDF files are not regular PDFs. The PDF/X file format is a different type of PDF specifically used to make the printing process easier. Perhaps that is the reason why you see the SWOP CMYK color profile. I read this as well:

 

Quote

PDF/X is a subset of the PDF ISO standard. The purpose of PDF/X is to facilitate graphics exchange, and it therefore has a series of printing-related requirements which do not apply to standard PDF files. For example, in PDF/X-1a all fonts need to be embedded and all images need to be CMYK or spot colors.

In a PDF/X file that has color-managed data, each color-managed graphic gets its own color profile, so even though the file as a whole is CMYK, individual graphics may be RGB (with calibration information).

Source: https://en.wikipedia.org/wiki/PDF/X

So even though the whole PDF/X document is in CMYK as a whole, each of the color-managed graphics (objects with an already assigned ICC profile?) can be sRGB, for example. Perhaps they get converted to a CMYK profile like SWOP when printing? I'm not sure, but @BofG, I assume that when exporting a PDF/X in sRGB all the graphics are assigned an sRGB color profile. As for your example, you are looking at the Output Intent. Since the PDF/X document is made for printing purposes, the Output Intent needs to be a "printer profile" (source) which I assume is SWOP CMYK in your case. The colors are actually in sRGB internally, I believe, but the printing process requires a conversion to CMYK once the document is printed. That is how I understood it, if someone knows more feel free to correct me :)

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I was aware of the "X" types, I know they are defined specifications (technically they are all still "just" pdf files). I tripped myself up as I had read the base pdf spec and knew that the output intent can also be an RGB profile (although having double checked it is noted that is only for pdf/a). When Designer gave me the option to export from an RGB file with the output profile "as document" I assumed the spec allowed for an RGB output intent.

The whole thing is one big usability nightmare :)

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