Converting to different color space

Dear Color Management Guru's,
I have a question regarding converting digital files between color spaces. Is it correct to convert a file from a large color space like Adobe RGB to a smaller color space such as sRGB, or visa versa?
Thanks in advance,
TC

I recently participated in a webinar and the instructor advised that you should 'never convert from from a large space like Adobe RGB to a smaller space like sRGB.
That's not good advice.
Convert when you need to convert. sRGB for web. CMYK for offset, etc.
Furthermore, the instructor recommends that photographers set their cameras to capture in the sRGB space and then later convert to a larger space if the output device can accommodate it.
Also bad advice.
Capturing in sRGB hamstrings you from the outset. Almost every output device (monitor, inkjet, digital press, offset press) can exceed the color gamut of sRGB in at least one dimension. sRGB is the lowest common denominator of color spaces.
My training as a film photographer makes me think that you would want to capture your files with as much data as possible.
You are correct.
At the very least, capture in Adobe98. But you really should be capturing in RAW. It gives you the most leeway when editing the image.
My thinking is that files that are recorded in Adobe RGB and converted to sRGB do indeed loose date. However, the data that is discarded are colors that do not exist in a sRGB file, may be outside of what is perceptible by the eye, is outside of the ability of the output device to record, or colors that do not naturally exist in the subject to begin with.
Well, kinda...
The changes are definitely NOT "outside of what is perceptible by eye."
When moving from Adobe98 to sRGB, you lose a significant amount of color in the blue/cyan part of the spectrum. Try it. Take an image that's been captured in RAW and processed into Adobe98 (or, just captured straight into Adobe98) and contains a deep blue sky or the kind of turquoise you see in a swimming pool or tropical ocean. Convert that image to sRGB and notice what happens to those blues and turquioses. Yuck. But, it is what it is. If the image is headed for the web, that's what you're dealing with.
One question:
Did you pay money for this webinar? You may want to try and get it back.
Beware of the advice you hear on the internet.

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I know I should have a better handle on this whole question by now, but am still confused by the 1.8 vs. 2.2 Gamma issue.
On the recent advice of an Apple PhotoServices tech, I've just changed my main display's Gamma from the default 1.8 to the darker 2.2 -- hoping to maximize consistency between what I see onscreen and what I'll receive in my printed Calendar order. (Everything else is still based on the default "Cinema HD" profile.)
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In Aperture, the image's thumb and its full-screen version look basically the same. But in iPhoto, that same image looks quite different depending on whether I'm viewing it as a thumb (or as an image placed in a Calendar theme), vs. when I double-click that image and see it in iPhoto's Editor window.
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Okay --
The plot thickens. I followed your suggestion, Terence, and did some tests. Here are the interesting (if confusing) results:
When I open anything from within the iPhotoLibrary folder using Preview, Preview gives the Color Profile info as follows:
Color Model: RGB
ColorSync Profile: Generic RGB Profile
This seems to apply to anything from within the iPhotoLibrary package, whether we’re talking images from the Originals folder, from the Modified folder, or thumbs from the Data folder. And they all (when viewed in Preview) look the same, and they all look “correct” in terms of general contrast.
BUT...
When I do a Finder “Get Info” on those same files, suddenly there are differences.
1) from the Modified folder:
Most images from the Modified folder now say (in Get Info’s “More Info” pane):
Color space: RGB
Profile name: Adobe RGB (1998)*
* (A few give the Profile name as “sRGB IEC61966-2.1”, and the one that got saved as a .psd file says “Camera Sync Profile”. The strange thing is I can’t seem to find any pattern between the images which were modified using my “external editor” -- Photoshop Elements -- vs. the ones which were edited using only iPhoto’s adjustment tools. The bulk of them all say “Adobe RGB (1998)” as the Profile Name.)
Note that these are the same images which, when opened in Preview, ALL claim the “Generic RGB Profile” -- and all look correct under those circumstances.
2) from the Data folder:
Meantime, ALL the thumbnail images which iPhoto has created for its Data folder, when “Get Info’d” in the Finder, all state their Profile name as “sRGB IEC61966-2.1”.
Open the same thumb image in Preview, and it’s back to “Generic RGB Profile” (as well as back to looking correct and not too dark).
3) from the Originals folder:
Finally, images from iPhoto’s Originals folder give no color profile data whatsoever in the “More info” pane of the Finder’s Get Info window. So is this the same as having the “Generic RGB Profile”?
In any case, here are three different folders (Originals, Modified, and Data), and iPhoto appears to be using a different color profile for the images contained in each one -- and in the case of the Modified folder, several different profiles.
Yet all of these images, when opened in Preview, appear to use the “Generic RGB Profile” -- and all appear as they should in terms of Gamma/contrast on screen -- while when viewed within iPhoto the same image will look quite different depending on whether it’s being seen in iPhoto’s regular window (as a thumb or as part of a Calendar layout, for instance -- all too dark) or in iPhoto’s editing window, in which case it suddenly looks fine.
The other mystery is why this discrepancy between iPhoto’s regular viewer and its editing window wasn’t apparent when my display was set to the default 1.8 Gamma; it’s only become an issue under the new (AppleSupport-recommended) 2.2 setting.
= = = = = == = = = = = = = = = = = = = = = = = = = = = = = =
My brain officially hurts now. (I guess this is just more evidence that Computers and the Internet will all be very nice if they can finally just get them working.)
Any help in interpreting this data will, as always, be much appreciated.
Thanks,
John Bertram
Toronto

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Hi,
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Thanks.
Message title was edited by: Brett N

Jeff Schewe wrote:
Bob_Peters wrote:
The rendering intent in the Export dialog is Perceptual.
Actually, an RGB color space to RGB colorspace is always only Relative Colorimetric...and adding Perceptual would only work with certain V4 ICC color spaces (you can find perceptual V4 color spaces for sRGB and ProPhoto I think but I'm not sure they would work in Lightroom anyway).
When using an RGB print output profile you can select either Perceptual or Relative and have the intents actually applied.
True.
The case of interest to me is when I have to print a lot of files using a third-party profile and maintain the original filename so it appears on the back. That is why I made the request more than a year ago.
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I am a new user of Lightroom and I find color spaces topic a bit confusing so far. My main question is: when exporting a photo, does Lightroom convert to a profile or assign a profile? Because there is no way to choose. I tried to export a photo with 3 different color spaces (sRGB, AdobeRGB and ICC profile from laboratory where I print my photos). After exporting them to JPEG it turned out that all of them look differently on my monitor - does it mean that Lightroom assigns a profile? If it was converting, shouldn't they have the same colours? What is more, after printing them in laboratory, results were completely different than I expected - the photo which had closest colours to what I saw in Lightroom was that in sRGB, but that with ICC of Lab was very different (much colder colours).
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I would like to have a little bit of control over what I'm working on, depending on whether I want to publish it on a website or print. I know that my monitor can be a problem (I have an iiyama with IPS), but surely there has to be any way to make results of my work a bit closer to my expectations.
Just for information, my workflow doesn't require Photoshop, as I rather prefer to use only tools from Lightroom. I hope that my problem doesn't require the use of Photoshop.
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Marcin S wrote:
Thank you for you helpful replies. Now I know a little bit more about it. But still, this is not completely clear to me.
My main question is: when exporting a photo, does Lightroom convert to a profile or assign a profile?
Both.
What you mean by both? How should I interpret it? I cannot choose "convert" or "assign", so how they both work together? What does it mean for me wanting to process photo and print in Lab?
I can only add, that those 3 photos which I exported to JPEG with 3 different colour spaces, they look different when viewing outside of Lightroom, ie. IrfanView. But when importing those JPEGs into Lightroom, differences are extremly slight. Is that because Lightroom operates in ProPhoto, which covers all colour spaces which I used, and other programs work in sRGB and those photos differently?
And the last question for now: will the hardware calibrator help in monitor which is, let's say, medium cost and medium quality? I mainly use it for preparing photos to put them on the website gallery, but would be nice if I could print better ones with a bit of certainty about what I will get from Lab.
Many thanks!!
Marcin
When you export a photo from LR, it converts to the colour space you select (e.g. sRGB) and embeds the appropriate profile in the exported file.
If your monitor were calibrated and profiled, and you view with a colour-managed viewer then images should look pretty much identical no matter which colour space you export in. (W7 Photo viewer is colour managed, the XP equivalent isn't, Mac s/w generally is. IE and Chrome aren't properly colour managed, Firefox is for all images, Safari is for images with embedded profiles. Other viewers vary.) With colour-managed viewers, the only difference should be with very highly saturated colours outside sRGB colour space (and then only if your monitor can display those colours).
LR is colour managed. If the monitor isn't calibrated/profiled then I think LR assumes the monitor has a colour space equivalent to sRGB (which is generally roughly right but won't be accurate). Internally LR uses ProPhoto RGB colour space in develop module, but uses Adobe RGB in Library, and previews are stored in Adobe RGB. However, the colour space LR uses won't explain why other viewers show things differently. It's simply that LR is colour managed (which means it converts to/from the image colour space), and I guess the other viewers you're using aren't; they just throw RGB data at the screen without converting.
Is it worth calibrating and profiling your monitor? Quite possibly. Does the colour and brightness vary with viewing angle as you move your head from side to side? If so, it may be TN technology, and perhaps not worth profiling. If it looks reasonably stable with different viewing angle then probably yes.

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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.
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/Steffen

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

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Hey Claude,
if it did not have an attached profile it is almost definitely in sRGB or, more rarely, Apple RGB. Lightroom always assumes sRGB for untagged files which is typically a safe bet. Photoshop generally uses the working space for untagged images. Since you had adobeRGB there, you should get a more saturated image in photoshop then in Lightroom. The same data is simply interpreted in a different color space leading to different colors. This has nothing to do with the monitor profile therefore and my initial hunch was wrong. So for untagged images in photoshop, you should usually assign sRGB to them instead of working space.
>As for calibration hardware we do use them here so I will use it but since the Mac was brand new out the box I assumed that it was ok...
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Please use the Acrobat SDK forum to reach the specialists who might help.

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Try editing the project as Pro Res 422.
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I wonder if it is considered normal behavior for a camera to produce AdobeRGB photos that are not tagged as such, or if it is a peculiarity of this particular brand or model.
(It also occurred to me later that the color space tag set by the camera only matters when shooting JPG, not when shooting RAW. The Camera RAW converter always converts to the color space that I have set PSE5 to, regardless of how the photo is tagged.)

ED
Your post has prompted me to investigate as I have recently come across the same issue.
I have a Canon 20d and have set it to use AdobeRGB colour space. I recently noticed that a JPEG image file appears as untagged in the metadata in Elements 5 Organiser but when in the editor it confirms it has the AdobeRGB space as the "Image/Convert Colour profile" instruction only offers to convert to sRGB or Remove Profile options. Furthermore the print dialogue confirms the presence of the AdobeRGB colour space. This has not been applied since importing from the camera as I have set the colour management option to "Let Me Choose" for this test.
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Hello all,
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3. Export the footage as "Uncompressed Microsoft AVI" V210 at 10bit YUV 4:2:2
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Looking forward to hearing some expert advice on the matter at hand!

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3. Use Avisynth to frame serve AVI to x264 (only line in avisynth script is AviSource ("inputYV12.avi") )
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Again - Thanks for making me think alternatives here!!
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Converting to different color space

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