Is Color Profile destructiv ?

[mallokw]

Hello everyone,

I ask myself a question concerning color profile management : if I open an adobe rvb profile image in Photoshop but apply an sRVB profile, is it possible to assign again the original profile and find again the original gamut colors (that are not included in the SRVB gamut) ? I mean, is the profile assignement a destructive fonction ? And also if we choose not to apply any color profile when image opening, is there any loss ?

Thanks for your help !

MK

[davescm · Accepted solution]

First, with the exception of a document having an incorrect profile, you don't 'Apply' an alternative profile. You 'Convert' from one color space to another.

With that out if the way, yes converting from a large colour space to a smaller colour space is destructive to any colours outside the gamut of the smaller space. Converting back to the larger color space does not expand those colours again.

For completeness of answer, Applying is non destructive in that only the meaning of the color values are changed. So changing back restores the original meaning, but only one of those meanings can be correct.

Dave

[mallokw]

Thanks for your answer and detailed explaination, Dave.

Regards.

Mallokw

[D Fosse · Accepted solution]

Not applying a profile on opening is completely pointless. All you're doing is remove the reference, so that the numbers are stripped of specific meaning. Two days later, you have no idea what the file is supposed to look like.

Not to repeat everything Dave said, but you open a file in the color space the file was created in. That's the correct profile. To move the file into a different color space, if you decide the original one isn't optimal, you convert. That changes all the numbers; everything is recalculated and remapped into the new color space, in order to maintain appearance. If colors are clipped in this process, they are gone forever.

It should perhaps be mentioned that converting is in fact slightly destructive, because you're changing all the numbers. It's like an adjustment. In a 16-bit file this is no problem, but with 8-bit files you might want to be careful.

[mallokw]

Thanks for these explanation on destruction when converting profiles...

Regards

[NB, colourmanagement net]

Depends what you mean by "Apply" 

I think you mean Assign - if so, then its not destructive, all Assign does is change the appearance by altering a conversion table within the profile - leaving the file numbers unchanged. 

For completeness I'll add that:

If you "convert" then, yes, it can be quite destructive because the numbers in the original file are recalculated in the conversion between the colour spaces.

Should you convert RGB file to CMYK, for example, then converting back will not give the original RGB values.

If you were to convert to a smaller colour space [say Adobe RGB to sRGB ] then, since any colour values beyond the boundary of sRGB have inevitably been clipped, you have lost the original information and converting back does not recreate the lost data. 

I hope this helps

neil barstow, colourmanagement.net :: adobe forum volunteer

[please do not use the reply button on a message within the thread, only use the blue reply button at the top of the page, this maintains chronological order]

[mallokw]

Message to NB_color management :

Thanks for your explanation.

If I understand well, there is a difference between Assigning a profile to an image inside a color space and converting a file into another color space (from rvb to cmjn for instance). According to what I understand, you mean that it is not destructive to assign a profile because it does not change the file numbers ? But if the profile is more restrictive than the first one (for example from adobe rgb to sRVB), there can be a loss, isn't it ?

I am a bit lost maybe...

Thanks for your help.

Mallokw

[davescm · Accepted solution]

Assigning does not change any numbers , only the colour that is displayed, as a result of those numbers, changes.. It's use therefore is to assign a profile when a document has no profile, or to assign the correct profile if the document has an incorrect profile embedded in it.

Convert is used when changing a document from one colour space to another. The numbers are changed so that the colours displayed remain as unchanged as possible. The aim is not to change colours and that aim can be achieved when the color space being converted to is large than the space being converted from.  However, if the color space being converted to is smaller , then the out of gamut colours (those that cannot be described in the new space) have to be changed. That change is not reversible by converting back again.

Dave

[mallokw]

Thanks Dave, that's clear now for me !

[NB, colourmanagement net]

Hi

There is NO loss when Assigning a profile, the only thing that changes is the profile assigned, so you can go back and reassign the earlier profile with no damage.

If you tell us what is is you are attempting to achieve we may be able to explain more fully. 

As dave explained, assigning a profile is normally only done to replace an incorrectly assigned one, although there are some possibilities for creative use of assigned profiles too.

https://www.josephholmes.com/profiles/about-my-profiles.

So, what does the Assigned profile do?

The assigned profile is the 'source profile' for that document in any later profile to profile conversion - 

so - a source profile is used in various ways 

e.g.

1: There's a constantly running conversion from the file's source profile to the monitor display profile to provide accurate viewing [this does not change the document]

2: Later, there may be a conversion from the source profile to the printer profile to provide accurate printed results.

Basically, the source profile tells the color management system what the RGB [or CMYK] numbers in your file mean in relation to visual appearance - 

More here about that: here is some reading on ICC profiles and how they work for you to provide accurate colour through the digital workflow: https://www.colourmanagement.net/advice/about-icc-colour-profiles/

I hope this helps

if so, please "like" my reply and if you're OK now, please mark it as "correct", so that others who have similar issues can see the solution

thanks

neil barstow, colourmanagement.net :: adobe forum volunteer

[please do not use the reply button on a message within the thread, only use the blue reply button at the top of the page, this maintains chronological order]