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Colour Space When Editing And Downloading to EPZ


Chris_L 5 5.0k United Kingdom
16 Nov 2018 1:51PM
Four full size versions here





Out of interest, the same images uploaded to the forum:

sRGB
250184_1542375996.jpg



sRGB
250184_1542376044.jpg



ProPhoto RGB
250184_1542376068.jpg



ProPhoto RGB
250184_1542376093.jpg

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Chris_L 5 5.0k United Kingdom
16 Nov 2018 3:02PM
Adobe RGB without a profile
250184_1542380253.jpg



Adobe RGB converted to sRGB but uploaded without any profile
250184_1542380306.jpg



Adobe RGB converted to sRGB with a profile (sRGB profile)
250184_1542380345.jpg



Adobe RGB saved with the correct Adobe RGB profile embedded and uploaded like that
250184_1542380391.jpg

Chris_L 5 5.0k United Kingdom
16 Nov 2018 3:15PM
So you can see the difference in skintone etc a little bit more clearly, click the thumbnail below to see the four large versions (click variations to compare)

All were edited in Photoshop in the Adobe RGB (aRGB) colourspace and output as 4 JPEG files.

Two had their colourspace converted to sRGB on save, one was tagged sRGB, the other was untagged

The other two had their colourspace left alone, one was tagged aRGB but the other was left untagged.

Tagged with a profile and profile embedded have the same meaning when talking about these jpeg files





Chris_L 5 5.0k United Kingdom
16 Nov 2018 6:15PM
After re-reading the thread I think that the OP might be making a really bad mistake.

I've done a screen video of where I think the workflow is wrong and will cause problems in future, I might have some of this wrong so would love to hear opinions of others

This is the video




JJGEE 14 7.5k 18 England
16 Nov 2018 7:28PM
Sad Far too technical / complicated for me.

I just process using the profile I am outputting too.
So for here it is sRGB and for printing ( on-line labs ) the relevant paper profile

Might be the wrong approach but processing in say Prophoto then having to " tweak " with the relevant profile in soft proofing mode seems like extra work me !
daniel66 3 61 United Kingdom
16 Nov 2018 11:13PM
My theory was that the colour had been converted from sRGB to Adobe RGB using "Assign Profile", which boosts the saturation (as below). You can't boost saturation using a conventional conversion between sRGB-Adobe RGB because the RGB values are altered to give you the closest possible match. Plus, you've already lost the wider gamut by truncating to sRGB in the first place, so there's no point to this conversion ordinarily.

The only thing that makes me doubt the above is that Firefox assigns an sRGB profile in the absence of an embedded profile, so would effectively undo any saturation increase and differences between the two files would probably be subtle (they look pronounced in my browser). It would depend to some extent on the monitor/browser combo and how the two photos have been edited.

293844_1542407971.jpg

293844_1542408077.jpg

293844_1542407968.jpg

Chris_L 5 5.0k United Kingdom
16 Nov 2018 11:31PM
That's what I'm saying in my video. Assigning a profile isn't a profile conversion though. You just tell the computer to interpret the numbers differently. If you convert, as you say, the program will avoid colour shift as much as possible.

If your workspace is sRGB and you bring in an aRGB image, as a new layer for example, it will be converted to sRGB and if it has an aRGB profile it will be treated as aRGB and converted accurately.

In the video I start with an 8 bit sRGB image in sRGB colourspace. When I assign an aRGB profile no conversion to a profile takes place, the profile of my workspace, my canvas if you like, remains as sRGB. The colour shift happens because the file's info is reinterpreted and rendered for the sRGB workspace.

Quote:
Firefox assigns an sRGB profile in the absence of an embedded profile, so would effectively undo any saturation increase

no it wouldn't.
1 ) Load sRGB image
2) Assign aRGB profile (this will give false colour / saturation boost)
3) Save as an sRGB jpeg with or without an sRGB profile and the damage remains
daniel66 3 61 United Kingdom
16 Nov 2018 11:55PM
If you assign an Adobe RGB profile to an sRGB image in Photoshop, it temporarily becomes Adobe RGB. This is a Bruce Fraser quote that knocks about on the Internet:

Quote:You could change profiles a thousand times via Assign Profile and the image would not degrade... inasmuch as the numbers in the file wouldn't change, this is true. But it would display incorrectly, and convert to any other space incorrectly, so it's fair to say that while the integrity of the data hasn't been compromised, and you can rescue the file by assigning the correct profile, for all practical purposes, it's hosed.

You can get back to where you were, but as soon as you save or convert with an assigned profile, it sticks. It can still be effectively undone after the event if the profile is not embedded (e.g. an sRGB file encoded in Adobe RGB via Photoshop will often be turned back into sRGB in Firefox).
Chris_L 5 5.0k United Kingdom
16 Nov 2018 11:59PM
I get what you are saying now.

1) sRGB image gets assigned aRGB profile - numbers are wrong, artificially boosting colours

2) Image is saved as an aRGB jpeg without an embedded profile

3) Browser assumes it is sRGB and actually reverses those numbers

What OP may have done at the save stage is converted to sRGB, keeping the false colour, doesn't matter that she doesn't embed an sRGB profile as that will be assumed colourspace in the absence of profile anyway?
daniel66 3 61 United Kingdom
17 Nov 2018 12:50AM
Yes to all three, with the slight caveat that not all browsers assign an sRGB profile to untagged images (in fact, Firefox is the only one that I know of). In other browsers, the colour will be subjected to Monitor RGB (no colour management), which will have a similar effect unless you happen to be using a wide-gamut monitor.

Your last assertion is also right. If you converted to sRGB by ordinary means ("convert to profile") after assigning Adobe RGB, you'd end up with a more saturated image than the original.


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