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Author Topic: Document Profile vs Printed Image  (Read 207 times)

nirpat89

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Document Profile vs Printed Image
« on: June 07, 2018, 03:02:17 PM »

OK, this is probably very basic but can't find answer to this precise question from usual sources:

If I created an image file from scratch using a broad swath of colors without any document profile, then make a copies of it and assign sRGB, AdobeRGB and ProPhotoRGB respectively and printed them all with Photoshop Manages Color using identical conditions: printer profile, rendering intent, etc, would I get different or identical prints?
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aaron125

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Re: Document Profile vs Printed Image
« Reply #1 on: June 07, 2018, 03:27:08 PM »

That would depend on whether or not the colours in your image exceeded the gamut limits of your output profile.

If you have defined one of your colours as L97a125b114, then, yes, youíd almost definitely see a difference as that colour should be outside the gamut of most any output device/profile (if said profile is of a physical, actual device which is currently available to the public at large - not some special, one-off prototype device which has almost magical properties, if the colour I mentioned is within its limit).

If you have a large number of colours which exceed the gamut of your output device/profile, again, youíd definitely see some differences between the various incarnations if your image. If you chose the Perceptual intent (and have just 1 single colour which exceeds the gamut of your output profile), itís highly possible (and quite likely) that some number of colours that are within the gamut of your output device will also be shifted, and shifted to different resulting colours for each of your source profiles.

And hey, donít sell yourself short, itís not a basic question at all. Not to mention, it shows an inquisitive mind and itís a great question, which would make me think that the person asking said question is going to be highly competent in the subject of colour management, if not already, then sometime soon.


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Doug Gray

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Re: Document Profile vs Printed Image
« Reply #2 on: June 07, 2018, 03:44:20 PM »

OK, this is probably very basic but can't find answer to this precise question from usual sources:

If I created an image file from scratch using a broad swath of colors without any document profile, then make a copies of it and assign sRGB, AdobeRGB and ProPhotoRGB respectively and printed them all with Photoshop Manages Color using identical conditions: printer profile, rendering intent, etc, would I get different or identical prints?

In gamut colors will be shifted except that neutral colors of sRGB and Adobe RGB will be quite close. All non neutral, in gamut, colors will be significantly shifted. Most out of gamut colors will also be shifted. They will be mapped to the printer's gamut boundary. Some may wind up at the same place but most won't.
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aaron125

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Re: Document Profile vs Printed Image
« Reply #3 on: June 07, 2018, 03:52:36 PM »

I might also add that technically, a colour canít be ďmadeĒ or created or even considered to be an actual colour unless and until it has an associated profile. This is because an RGB triplet doesnít define any real, Lab colour until it has a profile. Only Lab triplets define actual, physical colours and they too have a profile, that being the CIEL*a*b* profile. Iím not sure how Photoshop decides to show on-screen, the colours in self constructed files which have been made in a blank canvas. Perhaps it assumes the monitor profile to be both source and output, Iím not too sure.

All colours in an image are, in a manner of speaking, defined as Lab triplets because thatís one of the most essential functions of any profile, is to define how the source colours (be they RGB, CMYK or some other colour space type) will be converted to Lab output colours.


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digitaldog

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Re: Document Profile vs Printed Image
« Reply #4 on: June 07, 2018, 04:02:28 PM »

If I created an image file from scratch using a broad swath of colors without any document profile, then make a copies of it and assign sRGB, AdobeRGB and ProPhotoRGB respectively and printed them all with Photoshop Manages Color using identical conditions: printer profile, rendering intent, etc, would I get different or identical prints?
Yes, you should. The profiles define the scale of any numbers encountered. So if I tell you I live 1000 from you, meaningless. If I say 1000 miles OR 1000 feet, OR 1000 meters, the scale assigned is different, the numbers are the same and without a scale attached, ambiguous. R255/B45/G90 isn't the same color in two different color spaces. Assigning a different scale would provide a different meaning and hence, colored output.
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Andrew Rodney
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aaron125

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Re: Document Profile vs Printed Image
« Reply #5 on: June 07, 2018, 04:14:26 PM »

In gamut colors will be shifted except that neutral colors of sRGB and Adobe RGB will be quite close. All non neutral, in gamut, colors will be significantly shifted. Most out of gamut colors will also be shifted. They will be mapped to the printer's gamut boundary. Some may wind up at the same place but most won't.
If Absolute or Relative Colorimetric intents were chosen, then wouldnít the colours which are in gamut be output the unaltered, with respect to each source profile? As in, only those colours which are out of gamut should be altered?

Also, how could just some out of gamut colours be shifted, not all? AFAIK/understand, all out of gamut colours, by definition, must be shifted to some alternative colour which is within the gamut of the output profile/device?


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Doug Gray

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Re: Document Profile vs Printed Image
« Reply #6 on: June 07, 2018, 04:26:57 PM »

If Absolute or Relative Colorimetric intents were chosen, then wouldnít the colours which are in gamut be output the unaltered, with respect to each source profile? As in, only those colours which are out of gamut should be altered?
No. The key point in the OP's post is this: "... and assign sRGB, AdobeRGB and ProPhotoRGB..." When you assign a document RGB image the colors represented by the rgb pixels are established by the assigned colorspace. Until they have a colorspace they have no real meaning. This is quite different from converting from one colorspace to another but to do that the image has to be in a colorspace first.
Quote
Also, how could just some out of gamut colours be shifted, not all? AFAIK/understand, all out of gamut colours, by definition, must be shifted to some alternative colour which is within the gamut of the output profile/device?
Some OOG colors will wind up at the same place on the printer's gamut because gamuts have bumps and points and one that sticks out in the direction of an OOG color tends to get mapped to that place because it's closest.
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nirpat89

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Re: Document Profile vs Printed Image
« Reply #7 on: June 07, 2018, 06:20:19 PM »

Thanks Aaron, Doug and Andrew.  I'll digest these a bit.  Might have some more questions later...

:Niranjan.
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smilem

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Re: Document Profile vs Printed Image
« Reply #8 on: June 08, 2018, 08:19:15 AM »

If it's difficult with sRGB, AdobeRGB and ProPhotoRGB
imagine how it is with myriad of colorpaces for CMYK.
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