P: Export As is changes the colour values significantly when it converts 16 bit to 8 bit Prophoto

[davescm]

It looks like there is a colour management bug in Export As.

To test my working colour space is Adobe RGB, but I created a document in ProPhotoRGB and followed the process below:

a. I created a 16 bit document with a gradient running from RGB 07,53,25 to 50,98,50 in ProPhoto. (Readings are in 8 bit but document is 16 bit)

b. First I changed that to 8 bits - No visual change, Info from eydropper still shows gradient running from RGB 07,53,25 to 50,98,50 so no change in values either. That is as expected.

c. I stepped back in history to the 16 bit document

d. I used Export As to export a PNG in PNG24 format with no change of profile and the profile embedded. On reopening it opened in Prophoto but the values had changed as had the visual appearance. The gradient now ran from 0,77,33 to 53, 125, 60. Expected behaviour would be no change in teh colour values or visual appearance.

e. I repeated step "d" but used Save For Web (Legacy) again exporting PNG24 and with no change of profile and the profile embedded. This opened in Prophoto but the values were unchanged at RGB 07,53,25 to 50,98,50 Save for Web is working as expected.

So for some reason Export As is significantly changing the colour values when it converts from 16 bit to 8 bit Prophoto.

As a further test I converted the original 16 bit Prophoto document to Adobe RGB (which is my working space). The numbers changed to 0,77,33 and 53,125,60 but of course in the Adobe RGB space the appearance had not changed. Those numbers exactly match the numbers that were being appearing in the 8 bit exported Prophoto document. So for some reason, Export As is converting to 8 bit and at the same time changing the colour values to those appropriate for the Adobe RGB working space but then assigning the ProPhoto document space. By any definition this is a bug.

Dave

[davescm]

It looks like there is a colour management bug in Export As.

To test my working colour space is Adobe RGB, but I created a document in ProPhotoRGB and followed the process below:

a. I created a 16 bit document with a gradient running from RGB 07,53,25 to 50,98,50 in ProPhoto. (Readings are in 8 bit but document is 16 bit)

b. First I changed that to 8 bits - No visual change, Info from eydropper still shows gradient running from RGB 07,53,25 to 50,98,50 so no change in values either. That is as expected.

c. I stepped back in history to the 16 bit document

d. I used Export As to export a PNG in PNG24 format with no change of profile and the profile embedded. On reopening it opened in Prophoto but the values had changed as had the visual appearance. The gradient now ran from 0,77,33 to 53, 125, 60. Expected behaviour would be no change in teh colour values or visual appearance.

e. I repeated step "d" but used Save For Web (Legacy) again exporting PNG24 and with no change of profile and the profile embedded. This opened in Prophoto but the values were unchanged at RGB 07,53,25 to 50,98,50 Save for Web is working as expected.

So for some reason Export As is significantly changing the colour values when it converts from 16 bit to 8 bit Prophoto.

As a further test I converted the original 16 bit Prophoto document to Adobe RGB (which is my working space). The numbers changed to 0,77,33 and 53,125,60 but of course in the Adobe RGB space the appearance had not changed. Those numbers exactly match the numbers that were being appearing in the 8 bit exported Prophoto document. So for some reason, Export As is converting to 8 bit and at the same time changing the colour values to those appropriate for the Adobe RGB working space but then assigning the ProPhoto document space. By any definition this is a bug.

Dave

[TheDigitalDog]

On Mac: Export As (setting convert to sRGB and Embed) works fine, the preview is wrong as seen below.

Export As, (Setting do not convert but Embed) is wrong; I end up with the RGB Working Space (for me, ProPhoto RGB) and the original (in this case Adobe RGB (1998)) profile embedded. So yeah, it's screwed up.

Preview is wrong, result is correctPreview is correct, result is wrong

[davescm]

Thanks for confirming Andrew. So the bug affects Windows and Mac.

Dave

[J453]

Thanks for confirming and the bug details, Andrew. Engineering can take a look.

[BrettN]

I found through testing what happens is the 16-bit image is converted to Adobe RGB and then the orginial profile (ProPhoto) is assigned to the file. This results in the color numbers as well as appearance changing. If you Assign Profile with Adobe RGB, the appearance will then be correct. But this is definitely a bug and not how it should be working. I'm pretty sure we addressed something similar in the past, but it seems 16-bit files still run into the same issue. I found your bug report on our end and have updated it with the details of what I verified, we'll get working on this soon. 

[TheDigitalDog]

The other issue is the preview in the dialog when setting convert to sRGB.

[BrettN]

That's a separate and known issue (something else we are working on). Luckily, that is just the preview being inaccurate, the exported file should be correct. 

[davescm]

@BrettN 

Thanks for confirming. Let me know if you need any further testing.

Dave

[Mohit Goyal]

Hi all,  

We're happy to announce the release of Photoshop 23.2. This update includes the fix for this issue. To see the list of all fixed issues, click here

To update Photoshop to 23.2, click "Update" in the Creative Cloud desktop app next to Photoshop. More detailed instructions for updating  

Let us know if the update resolves the problem for those affected and share your feedback with us.  

Thanks,

Mohit