Software - - Adobe RGB vs S-RGB conversion issues with JPEG

Dropbear67 · #1 11-26-2006, 01:47 AM

When I open a JPEG that has a SRGB colour pallete saved and convert it to Adobe-RGB within photoshop (which is my standard colour pallete) it works fine and I can work on the image ok, however after I save the .PSD and convert back to JPEG I find the resulting JPEG file quite different from what I see in Photoshop.

The colours are generally a lot more muted-as if the saturation has been turned way down. It's really quite annoying. I don't get this issue if no colour conversion on image opening has occured.

Does anyone have an explanation on why the resulting JPEG is quite different?

Swampy · #2 11-26-2006, 07:45 AM

Dropbear

Why, oh why are you saving back as JPEG? Are you saving a PSD or TIFF version of your file for archiving?

If you are saving out as JPEG for upload in email or to a web page, you have to remember that every time you save a file as JPEG you lose information. JPEG is what is considered a "lossy" format. Resaving JPEG files as another JPEG file is like making a photocopy of a photocopy. Each succeeding "save" deteroriates the file even more.

If you are saving to JPEG for use in email or Web graphic, use the "Save for Web" option in Photoshop. You will still encounter the lossy problem, but you will have much more control over what you lose. I know the file may become desaturated, but you can plan for this in advance by adjusting curves or levels to darken slightly before "Save for Web". If you have saved your work as PSD or TIFF (with layers), you can then trash the JPEG after uploading it.

Always save your work as PSD or TIFF for future reference. These are lossless file formats. I always use an auto "batch" action to save my JPEG files as TIFF before I ever start working on them.

Dropbear67 · #3 11-26-2006, 02:59 PM

Swampy... These issues on not getting the same colours is only occuring after saving to JPEG *AFTER* I've done a colour conversion when opening the image.

I can't avoid saving images to jpeg when I'm giving them to people to look at or putting them up on the web. Of course I am saving them as .PSD files first. I can have the .PSD file open in photoshop and the jpeg side by side and see the differences in colour in this circumstance.

It's *NOT* just a jpeg lossy thing, it happens after an image saved in SRGB format is opened as an Adobe RGB format in pshop. Well, at least that's all I can track it down to being.

Swampy · #4 11-26-2006, 03:10 PM

My bad... I thought you were getting color shift when saving.

There is a difference in the spectrum of colors available between SRGB and RGB. SRGB is more robust than RGB. Have you tried changing your color space to SRGB in Photoshop then opening SRGB files using that color space? (Edit>ColorSettings>SRGB)

Dropbear67 · #5 11-26-2006, 03:15 PM

Quote:

My bad... I thought you were getting color shift when saving.

Well...I think I am... That's the issue..

For images where I do a colour space conversion when opening,I have the image just the way I want it in photoshop, save it to jpeg and bam, the colours are washed out - less intense etc ... This only seems to be the case where I have done a colour space conversion on opening the file.

mistermonday · #6 11-26-2006, 03:39 PM

Dropbear, it sounds like there is a problem in the way you are managing color (or not).
Firstly, check you Edit>Color Settings. Under the "Color Management Policies", select "Preserve Embedded Profiles" for all of them. Then make sure you check all 3 boxes for profile mismatches. This way you will always know when you open or paste if you have a profile mismatch.
The other thing to be sure to verify that when you are saving a file as jpg, do a File>Save As and make sure that the box to save an embedded color profile is also checked.
Adobe RGB has a much wider color gamut than sRGB. If you save an Adobe RGB file but you do not embed the profile, anyone who opens it in a system that is either sRGB or is not managing color (like all browsers), then your brilliant colors will be duller and less saturated.
If you are converting an image from sRGB to A RGB, if you uploading to web or sending to someone whose graphic s/w does not manage color, make sure you save their copy as sRGB or it won't look that great.
Regards,
Murray

Swampy · #7 11-26-2006, 04:20 PM

Thank you for the correction, Murray.

I had said SRGB had a wider color range than, but I did have sRGB and RGB backwards.

mistermonday · #8 11-26-2006, 04:26 PM

Swampy, that's OK there are now soooooo many new color spaces, its hard to remember which is which. Moreover the gamuts of some of them are unevenly shaped to where you can not make a blanket statement about the entire gamut.
Regards, Murray

Dropbear67 · #9 11-26-2006, 05:00 PM

Quote:

If you are converting an image from sRGB to A RGB, if you uploading to web or sending to someone whose graphic s/w does not manage color, make sure you save their copy as sRGB or it won't look that great.

I think this may be the problem I am having. I like to work in Adobe RGB within photoshop but I don't think I'm saving them back as sRGB when I finish. Is there a particular step to do this?

Maybe for images that are given to me in sRGB mode I should just stick to working with them in sRGB mode and not colour converting them?

mistermonday · #10 11-26-2006, 05:16 PM

After you have finished working in A RGB, if you are using CS2, go Edit>Convert to Profile, and select sRGB. If you are using CS or earlier version, (if my memory serves me correctly) go Image>Convert to Profile - anyway I thing it is at the very bottom of the image menu. You can save it using Save As so that you can keep two files, one with each profile. Or keep the psd file as Swampy recommended and then you can spin off sRGB jpgs or Argb files to your heart's content. BTW, A RGB may allow you to take advantage of the wide gamut and brilliant color that many ink jet printers can now print. So that could be an advantage to working in A RGB.
One more warning: If you are sending a bunch of images to be printed at a big box store with1 hr service, and you want to have really great looking prints while taking advantage of the $0.20 per copy, make sure you save them as sRGB. Those mass production Kodak or Noritsu processors do not respect color profiles - all images are assumed to be equivalent to sRGB.
Regards, Murray

Dropbear67 · #11 11-26-2006, 05:38 PM

Cheers Murray and swampy.. you've been champs mate.. Have it sorted now..my jpegs look shiny

Littlecoo · #12 11-26-2006, 07:45 PM

Microsoft Imaging (most windows users have this at the very least) can open flattened tiffs and does have some basic colour profile management that will recognise standard embedded profiles and display them (and default settings are such that it should)... so tiff files are feasable. I also use pdf files if I want to have some control over image colour profiles and how it displays.
For the hell of it I deliberately set up a colour profile missmatch(sRGB and aRGB in a sRGB space), eye-droppered some colour chips for ease of comparison, Mmmmm...shifty!