GIMP 3.0.2 bug (?) - TIFF image

[dziadekles]

The image: CR2 file. The system: Win 11. Display profile: none.
No processing was applied in any of the images listed below.

I compared the following:

-CR2 file opened in RawTherapee
-and subsequently opened in GIMP
-GIF export from GIMP, viewed in Photos & GIMP
-JPG export from GIMP, viewed in Photos & GIMP
-TIFF export from GIMP, viewed in GIMP

-CR2 file opened in DPP4, (Digital Photo Professional)
-TIFF created in DPP4, viewed in Photos & GIMP

CR2 file opened in PW8, (Picture Window 8)
-TIFF created in PW8 viewed, in Photos & GIMP

All these images match in terms of color and lightness (they are identical, at least to my eyes).

The TIFF files created in GIMP, DPP4 and PW6 all can be opened in GIMP and look the same.
The TIFF file created in GIMP can be opened in Photos, but the luminosity is off (the image is much lighter).
The TIFF file created in GIMP can't, however, be opened in DPP4 or in PW8. 


Conclusion: there is some problem with file conversion in GIMP3.0.2. The TIFF standard is not supported to the extent that it can be opened with different photo processing software. Neither DPP4 nor PW8 have this problem: their respective TIFF files are fully interchangeable, produce identical images using all processing software or image viewers - but can't be opened in GIMP...

This looks like a bug to me (unless there is some sensible explanation), but I am not sure how to report this...

[rich2005]

You might be lucky, there is a Gimp dev who does visit and is involved in color management.
I would give details of the actual color profile used that gives that odd version for the tiff image.
Edit: Just had another compare with RGB tiff images and I can not repeat your result between Gimp and other file viewers.
Maybe post that tiff image (or similar) and perhaps a cause determined.

-------
Differences in the way the same image shows in different programs has been noted in the past, especially CMYK jpegs, but I believe improved now.

I would be careful using MS Photo (this is MS Photo ?) it will automatically brighten images.

If I do a comparison  kubuntu linux / Gimp 3.0.2 / Krita 5.2.6 A very bright image that will never print as RGB - too much out-of-gamut. There is no real difference betweem Gimp soft-proofing / CMYK export (SWOP) and the exported image opened in Krita. As a comparison the CMYK file open in a non-color-managed file viewer.

   

Typo - that should be CMYK - I once read a short story where everything was typed one key to the left
...but then I have a run-of-the-mill Brother inkjet, know the limitations of computer display / printer and print very much as intended from RGB images. If I send off to a commercial printer, then it depends on the printing company as to color profile used.

Edit: Just had another compare with RGB tiff images and I can not repeat your result between Gimp and other file viewers.

[dziadekles]

(Yesterday, 09:12 AM)rich2005 Wrote: You might be lucky, there is a Gimp dev who does visit and is involved in color management.
I would give details of the actual color profile used that gives that odd version for the tiff image.
Edit: Just had another compare with RGB tiff images and I can not repeat your result between Gimp and other file viewers.  
Maybe post that tiff image (or similar) and perhaps a cause determined.

-------
Differences in the way the same image shows in different programs has been noted in the past, especially CMYK jpegs, but I believe improved now.

I would be careful using MS Photo (this is MS Photo ?) it will automatically brighten images.

If I do a comparison  kubuntu linux / Gimp 3.0.2 / Krita 5.2.6 A very bright image that will never print as RGB - too much out-of-gamut. There is no real difference betweem Gimp soft-proofing / CMYK export (SWOP) and the exported image opened in Krita. As a comparison the CMYK file open in a non-color-managed file viewer.



Typo - that should be CMYK - I once read a short story where everything was typed one key to the left
...but then I have a run-of-the-mill Brother inkjet, know the limitations of computer display / printer and print very much as intended from RGB images. If I send off to a commercial printer, then it depends on the printing company as to color profile used.

Edit: Just had another compare with RGB tiff images and I can not repeat your result between Gimp and other file viewers.

OK, part of the puzzle found its explanation:
It appears that after opening RAW file in GIMP and converting to the default color profile - all exports WITH THE EXCEPTION of TIFF are saved with the default color profile. TIFF exported by GIMP needs to be saved WITH color profile.
Both files, however, show in GIMP as identical images...

But both files still CAN'T be opened in DPP4 or PW8.

One more thing: TIFFs from DPP4 and PW8 have the same size: 48,483 KB.
The TIFF from GIMP is 96,361 KB (without profile) and 96,362 KB (with profile).

EDIT: this makes sense for TIFFs from PW8 and DPP4: Image size is 3514x2340 pixels, so TIFF file size is 3514x2340x16/1024 = 48,181 KB (plus some embedded TIFF data).
So - why is TIFF from GIMP TWICE THE SIZE?

There is definitely something strange with the TIFFs created in GIMP.

[rich2005]

I know you are wanting to explore Gimp 3 but since you are using Cannon stuff why not stick with Digital Photo Professional.

..sorry.. linux user here, no idea about Picture Window 8

File size ? have you checked the bit depth ? 8 / 16 / 32 and encoding linear / non-linear

Hopefully a Gimp dev will come along and examine the issue.

[dziadekles]

(Yesterday, 01:16 PM)rich2005 Wrote: I know you are wanting to explore Gimp 3 but since you are using Cannon stuff why not stick with Digital Photo Professional.

..sorry..     linux user here, no idea about Picture Window 8

File size ? have you checked the bit depth ?  8 / 16 / 32 and encoding linear / non-linear

Hopefully a Gimp dev will come along and examine the issue.

 no Linux here, I am on Win11 and too old to learn new tricks. 
Your comment about encoding may be actually pointing in the right direction - since the TIFFs produced by GIMP are exactly 2x bigger than standard 16-bit TIFFs.
I am getting some questions from the GIMP team, and also I am providing more data and info - including the TIFFs in question.
Hopefully all will be explained and/or fixed.

[rich2005]

Ok, you have Alx Sa on the case, good job of reporting an issue.

Just for info, you can get image info just from the Gimp Window, where default setting shows bit depth and image size in pixels.  Not a big image but it is 32 bit floating point.

It does have a colour profile but it is just the default Gimp sRGB

   

[dziadekles]

(Yesterday, 03:33 PM)rich2005 Wrote: Ok, you have Alx Sa on the case, good job of reporting an issue.

Just for info, you can get image info just from the Gimp Window, where default setting shows bit depth and image size in pixels.  Not a big image but it is 32 bit floating point.

It does have a colour profile but it is just the default Gimp sRGB

Thanks, I am in the process of rapid info intake right now   and as far as GIMP - I have spent altogether maybe 12 hours on it...

I think another part of the puzzle uncovers itself:

I looked at the image info for both TIIF files - one exported W/O saving color profile, and another exported WITH it.
They are both 32-bit floating point...why? 
Firstly - I do not know of any programs which can use 32-bit image for processing.
And if they can - then what's the advantage?

I always used RAW files, converted to 16-bit TIFFs, processed the TIFF, converted to sRGB for screen and printing. 
OK, some people may want 32-bit for some mysterious reasons - but here are the questions:

-why both TIFFs (the one exported WITH and the one W/O color profiles) have identical info (looking at the Image Properties - screenshot attached).
-why are they both exported as 32-bit floating point by default (well, that explains their double size and problems with opening in other image editors...) - if Export Image as TIFF option is not checked (screenshot attached)?

Don't take me wrong: I really like the new incarnation of GIMP. Yes, this is a community project, and it is free, so there is no point of wanting something else: WYSiWYG and all...
Anyways, I am sure that someone smarter than me will sort it out (although sometimes there is such a thing as too much of a good thing).