Color space conversion problem when importing JPEG's

Question

Hi,
I'm currently playing with the trial version of LR. While importing JPEG's with different color spaces (sRGB and Adobe RGB) to LR I've noticed a strange effect: There is a small but noticable difference in color, depending if the JPEG was previously saved in AdobeRGB, or sRGB. All the images I've tested so far should not contain critical colors that exceed normal sRGB. When opened in CS2 both versions of a JPEG, AdobeRGB and sRGB, typically look perceptually identical, no matter if I leave the sRGB image to sRGB, or convert it to the working space (AdobeRGB). Also my color-managed image viewer behaves as it should. So I don't think it's a matter of the different color spaces.
Looking at the imported images in LR I would say that the AdobeRGB image is correctly converted while the sRGB image suffers from a slight reddish cast, most noticable in skin tones. The effect is not as strong as if I would load the sRGB image into CS2 and skip color conversion to my working space (AdobeRGB).
The sRGB versions of the JPEG's were obtained from the AdobeRGB JPEG's using CS2 for conversion.
Anyone else here experienced a similar problem? Is this a bug in the xRGB-to-ProPhotoRGB conversion of LR, or a feature?
/Steffen

Answer 1

Hi Uli,
thanks for pointing me to your thread. I followed the discussion with great interest. Actually, I think the effect I am describing here is of different nature and a LOT stronger, at least for the type of images I've tested.
I did some more experiments yesterday with interesting results:
1) When I export a processed RAW from LR to JPEG or PSD, no matter what Color Space (I tested AdobeRGB, sRGB and ProphotoRGB), and re-import those JPEG/PSD's to LR, they look absolutely identical to the RAW I started with. Also, at first glance, they look similar when opened in CS2, but only because I tested with color images. I can indeed see small differences when testing with B/W, as you described in your "Color management bug" thread.
2) When I change the color space of an PSD or JPEG inside CS2 (I used the default setting 'relative colorimetric') and save it to JPEG and then import this JPEG to LR, colors are far off. The strength of this mostly reddish color cast depends on the color space of the imported JPEG, strongest for Prophoto, less strong for Adobe and sRGB. Interestingly, when I convert the color space inside CS2 and save the result to PSD, it will display correctly when imported in LR. Another interesting side effect: the thumbnails of LR-exported JPEG's in the "Open" dialogs of CS2 and LR (I guess those are not color-managed) show the typical color-flatness for the Adobe and even more the ProPhoto version. For the CS2-converted JPEG's, all thumbnails look just a colorful as the thumbnail of the sRGB version.
3) Such an image which doesn't display correctly in LR will keep its color cast when exported again to a JPEG (not sure about PSD). So something goes wrong with the color conversion during the import of such CS2-converted images.
My explanation so far is that CS2 uses a slightly different way of coding the colorspace information in the metadata of JPEG's which somehow prevents LR to recognise the color space correctly.
Can you confirm this behaviour?
Steffen