Missing/Mismatch Colour Profile - Best Practice

[bazj99]

Hi,

What is the best way to approach a missing/mismatch colour profile message when opening an image in Photoshop?

Is it best to convert to the working space profile at the opening dialogue, or do nothing ('Leave as is' or 'use the embedded profile') at the opening dialogue and convert to working space after opening using Edit->Convert to profile.

Why is there a difference in colour doing it the two ways, when essentially you're asking for the same thing (to convert to the applications default working space), just at different stages?

Many thanks in advance.

Barry

[Stephen_A_Marsh · Accepted solution]

For an untagged RGB image, the best option is to not convert and initially use the working RGB. Then visually and numerically (Lab or CMYK info values) inspect the image to see if the default working space is appropriate or not. You may find that assigning another RGB has a better visual and or numerical result.

https://prepression.blogspot.com/2014/06/rgb-icc-profile-roulette.html

If the RGB image has an embedded ICC profile, then you should initially honour/accept this. You can then visually and numerically inspect the image to see if assigning another profile would change the appearance favourably over the tagged ICC profile in the file. You would need to ask yourself why you don't trust this "label".

There is often no need to convert from the source profile to your working RGB, unless the source profile isn't a working space profile. If the source profile is a device profile such as a monitor, scanner or printer profile then it is best to convert it into a predictable, "well-behaved" working RGB space for further editing. One would generally convert from a smaller space to a larger space to avoid gamut clipping.

Notice that I have not commented on CMYK mode files, as they have different considerations and are generally best not converted.

[D Fosse]

My standard advice is to disable the "mismatch" warning permanently. There is absolutely no reason why the embedded profile needs to match the working space. 

The working space is just a fallback default if there is no embedded profile. If there is, which there always should be, it will override the working space. In other words, the working space is not important, and the message tells you nothing useful.

Photoshop's default policy is to "preserve embedded profiles". Don't change that. This is how Photoshop is supposed to work. That you even have the two other options, "off" and "convert to working", is mainly a leftover from back when color management wasn't widely supported. Today, those two options just cause problems, and if Photoshop was written today, it would probably be hard-wired to "preserve embedded" - like e.g. Lightroom Classic is.

In short - if the image has an embedded profile, use that, unless it's a very non-standard profile that may cause problems later on. Then you convert to the closest standard profile. Standard document profiles are sRGB, Adobe RGB and ProPhoto RGB. Lately, Display P3/Image P3 is increasingly used in the Mac community, although it is basically a display profile and so that practice is a little questionable.

[bazj99]

@Stephen_A_Marsh @D Fosse 

Thank you both for your replies.

So if we are printing on a digital press that is running to Fogra39 standard, we should leave CMYK images with whatever they have embedded rather than converting to Fogra39. I had though that by converting to Fogra39 it would give a better representation on how it would print on a printer running to the Fogra39 standard. Is that not the case?

Kind Regards,

Barry

[Stephen_A_Marsh]

So if we are printing on a digital press that is running to Fogra39 standard, we should leave CMYK images with whatever they have embedded rather than converting to Fogra39

By @bazj99

Keep in mind that the bulk of my previous comments were specifically regarding RGB and that the only mention of CMYK was a single unqualified sentence.

You have now qualified that this is regarding digital output. CMYK for a traditional press vs. digital press may have very different concerns than digital.

The digital press may be set to *simulate* the F39/ISO Coated v2 offset press specification (not a standard), however, it will still be transformed into the final digital press colour space for the digital press "ink" and media. Therefore the original CMYK separation values will probably be transformed anyway. I doubt that many digital press workflows are configured to send through the source CMYK values without a transformation to the press/substrate profile.

If the CMYK images have a F39/ISO Coated v2 ICC profile embedded in them, there should be no reason to convert as this would be a null transform if the intermediate simulation space is F39/ISO Coated v2.

If the CMYK images have a different ICC profile embedded in them than F39/ISO Coated v2, there are two choices:

1) Honour the CMYK values, ignore the profile

2) Honour the ICC profile and convert the values to the simulation profile

There are pros/cons to both and it is conceivable that either approach may be the correct or incorrect approach for any given image.

I had though that by converting to Fogra39 it would give a better representation on how it would print on a printer running to the Fogra39 standard. Is that not the case?

By @bazj99

If the CMYK images have a different ICC profile embedded in them than F39/ISO Coated v2 does it mean that the file's CMYK values are incorrect and the profile is correct? Or could it be that the file's CMYK values are correct and the ICC profile is incorrect? 

As long as you make it clear to customers who submit files what will happen, they can't complain that they didn't know that your chosen course of action might lead to unexpected or incorrect reproduction of their intent.

[bazj99]

Hi Stephen,

Do you know why there is a difference in colour when converting at the opening dialogue compared to leaving at that stage and converting using the Edit -> Convert menu.

Thanks

[D Fosse]

If you do not convert when opening, you need to choose "preserve embedded". Then there cannot possibly be any difference between the two, because both are the same conversion (original profile > target profile).

Problems happen with the third option (discard profile). Then you throw it all to the wind and anything can happen.

But again, as I said, the best advice I can give is to completely disable this dialog, and stick to "preserve embedded profiles" as a universal policy. That's how Photoshop is intended to work, and with this policy you are always safe.

[Stephen_A_Marsh]

@D Fosse 

Agreed, even more so for CMYK with black channel considerations.

[bazj99]

Many thanks for your help.

[bazj99]

I just dont understand why the colours are different when 'converting the documents colours to the working space' on opening compared to opening using embedded profile and then converting using the Edit->Convert to profile.

[D Fosse]

They cannot be different unless you have untagged files (without an embedded profile). Then the working space takes over, and that may not be the color space the file was originally created in. Then you get a color difference.

[NB, colourmanagement net]

@bazj99 Personally, I'd generally advise users to leave profile mismatch checked, for 2 reasons,

1: As evidenced by it's, embedded profile, an RGB file may be in, say, a scanner colour space (which is quite possibly non linear), thus it should be converted to a working colour space (those are linear) before editing since edits in a linear colour space are more predictable.

2: With a CMYK file - then in your situation you need to know that it's been converted (separated) to CMYK incorrectly. 

When you receive CMYK image files which have been converted to a colour space other than a FOGRA 39L one (as evidenced by the embedded profile)  you could proof as-is and, if the appearance is OK, just accept and print the file.

IF appearance is poor and you need to convert then it's best done using a colour server (GMG make a great one) otherwise any black-only areas like text or drop shadows could get converted to 4 COL.

Best practice is to ensure your clients convert to the right CMYK colour space.

I hope this helps
neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management
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[D Fosse]

Personally, I'd generally advise users to leave profile mismatch checked, for 2 reasons,

1: As evidenced by it's, embedded profile, an RGB file may be in, say, a scanner colour space (which is quite possibly non linear), thus it should be converted to a working colour space (those are linear) before editing since edits in a linear colour space are more predictable.

By @NB, colourmanagement net

There is a much simpler way:

It's not that the mismatch warning does any harm in itself. It's more that it misleads inexperienced users into thinking it's actually important, and that the document profile should match the working space. Every time that warning comes up, this misconception is reinforced.

So to be absolutely clear: the embedded profile does not need to match the working space.

Now CMYK comes up, which wasn't originally mentioned. All explained above, but it needs to be particularly emphasized that there are scenarios where you don't want to convert at all. It mainly involves overprinting black plate, 0-0-0-K. This applies to e.g. text, but also things like comic book illustration and so on. If you convert, those K-only blacks will be turned into four color blacks, and that can be a minor disaster in some situations.

[NB, colourmanagement net]

@D Fosse "

There is a much simpler way:

It's not that the mismatch warning does any harm in itself. It's more that it misleads inexperienced users into thinking it's actually important, and that the document profile should match the working space. Every time that warning comes up, this misconception is reinforced."

Yeah, that does miss a step, BUT users have to be aware to take notice and I prefer the warning so they don't forget. I think the mismatch IS important and users need to understand what to do about it. 

Just my 2p having worked with hundreds of clients, many of whom were forgetters. 

I hope this helps
neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management

[Conrad C]

I strongly agree that it’s better to leave the mismatch warning deselected, and instead, keep an eye on each document’s profile in either the document window status bar and/or the Info panel, which lets you decide later (researching if needed) after determining if a profile conversion is even necessary.

Partly because I agree with D Fosse that generally, the document profile does not need to match the working space in current workflows. (In the past, noticing profile mismatches with the working space was much more important when most printing workflows enforced device-specific CMYK from end to end, but not with today’s workflows that are more color-managed, device-independent, and even RGB-based with a late conversion to press-specific CMYK. In a current late-binding workflow it almost doesn’t matter what profile an image has, it’ll get converted to the correct press color space eventually.)

Another big reason is user fatigue when opening many documents. When the mismatch alert comes up, it is modal. Which means Photoshop cannot continue to be used until that dialog is closed one way or the other…all work stops. This is very frustrating for the user if they don’t actually know what the profile is supposed to be or if the current working space is actually what opened documents should all be converted to. And if they open another image, they go through it all again. There is a risk of making a big mistake by the user guessing, or for a user to just hit OK for everything so that they can keep working. (If it is preferred that a user click OK for everything, then interruptions should be avoided by disabling the mismatch warning and enabling the Convert To option, for a silent conversion of all images to the working space.)

Also (this has happened to me), when the mismatch warning is on and you are importing multiple selected files at once, now the dialog box is going to appear for every image you selected, over and over again. I found this to to be extremely frustrating when I had left the mismatch warning on after some testing, and then tried to place a bunch of images at once.

If instead there is no mismatch warning but each document profile is visible in the status bar or Info panel, then all documents can be opened first and then the user can take the time to think through whether each image needs a conversion, without being impatient to get through modal dialog boxes.