Colour in h.264 slideshows created by Lightroom 3
This article is about a Lightroom 3 quirk we’ve recently become aware of: a colour shift when exporting slideshows as self-contained movies for use iPhone, iPad, YouTube and Facebook. We see the problem on all our Macs; we haven’t tested yet on Windows.
Summary of the issue
Playing back self-contained slideshow movies that you create using Lightroom 3 might show significant colour shifts if you export at 720p or 1080p. (Tests done on Mac OS X 10.6.4 and Lightroom 3.2.) Update: a 720×480 movie also shows the issue, and I’ve updated the example zip file to include a sample at this resolution.
Background
We do post-processing work for weddings shot by a local professional and, as part of the package of print-ready and screen-ready images we produce for him, we now include two movie slideshows with soundtracks. (Good for wedding gusts to have a chuckle over.) The smaller slideshow movie (480 pixels) is for use on an older iPhone or Android device and the bigger one (at 720p HD) is for upload to Facebook or YouTube, or for use on an iPhone 4 or iPad. Both movies use the h.264 codec, which allows excellent compression and relatively small file sizes.
Colour shift at 720p and 1080p
What we’ve noticed is that the colour palette displayed in movies exported from Lightroom 3 varies with movie resolution and is not consistent when played back in different players; in particular, the 720p and 1080p sizes, coming straight from Lightroom 3, display different colours from the other sizes. (Other resolutions show some subtle colour shifts but their colours are still acceptable and are consistent across sizes. Not so for 720p and 1080p.)
Here are are some screen shots from two example slideshows, with a gaudy background colour wash, chosen so that you can see the affect on both warm and cool tones.
Above: a screen shot of a 480-pixel movie slideshow playing.
Below: a screen shot of 720p slideshow. Resolution aside, no differences in the settings between the two. Compare the colour of the blue MINI in the two pictures above and below.
Finally, below is the picture exported from Lightroom 3 as a JPEG in sRGB colour space, to act as a comparison against both movie screen shots. You can see that the 480-pixel shot is closer to displaying accurate colour.
When we originally saw the phenomenon, we were using Lightroom 3.0; the screen shots above are from the Mac version of Lightroom 3.2. The player was Apple’s QuickTime Player X.
Different results when movies are played in VLC or QuickTime Player 7
If you use VLC (free for the Mac, Windows and Linux) or QuickTime Player 7, colour is at least consistent across all movie sizes but is consistently wrong—VLC 1.1.3 (current version as of August 2010) and QTP 7 running on Mac OS X 10.6.4 appear to be ignoring the display’s ICC profile (ColorSync profile).
Download examples of h.264 slideshows from Lightroom 3
Here’s a seven-megabyte zip file containing a single-image slideshow at different movie resolutions, together with a 960-pixel JPEG of the same image in the sRGB colour space, for comparison. All the movie files came directly from Lightroom 3.2, with no change of settings between exports other than output resolution. You might notice that the colour in the 720p and 1080p versions are different from the rest.
AVC vs h.264
In QuickTime Player X, the 720p and 1080p clips also list “AVC” instead of “h.264″ as the codec used; in theory, h.264 and AVC should be identical so it’s not clear whether different code is actually used by Lightroom 3 to generate these two HD resolutions or whether QuickTime Player just identifies the same codec differently at these particular resolutions. In other words, this particular point could just be a client issue. QuickTime Player 7 lists all the movies’ codecs as being AVC and get the colour wrong on all of them, too.
The importance of your display profile (ICC/ColorSync)
Our tests suggest that your display profile will make a big difference in determining whether you see these colour shifts or not. The further it is from a regular, canned sRGB or “Color LCD” profile, the more difference you’ll see between the two AVC files (720p and 1080p) and the rest. Switch to a custom profile generated with a colorimeter or spectrophotometer and there’s a good chance you’ll see a bigger difference. (If you want see a huge difference between the two AVC files and the rest, set your display’s profile to “Wide-gamut RGB”.)
Preliminary advice on h.264 movie slideshows from Lightroom
We’re reporting the issue to gather feedback and direct it to the right place. We don’t have any definite answers (we don’t even know whether the problem is definitely a Lightroom issue or an OS issue) but here are some suggestions.
- Test your own h.264 slideshow output from Lightroom 3 at different sizes to see if you experience the problem and if you do, decide whether it’s a show-stopper. (It may not be—our example is likely to show a worse problem than most real-life files.) Compare your own results with our zip file of examples.
- Be aware that your clients who use different movie players might see different results from you when you provide h.264 output at 720p or 1080p. The differences will probably most important for product photography, portraiture and fashion. Colour in slideshows with music isn’t usually quite as critical as it is with files you submit to a stock agency or an art editor so this may not be a huge problem. If your results vary from ours, please report your findings on the Adobe Lightroom support forum, where I’ve just started a new thread about this problem. If you report the issue, provide as much information about your environment as you can (hardware, OS version, Lightroom version, display profile, details of media player).
- We only see the problem in 720p and 1080p slideshow exports from Lightroom 3. One workaround for now is to stick to 480-pixel or 960-pixel output. That way, when it’s played on another colour-managed computer in QuickTime Player, its colour will stand a better chance of being acceptable.
If and when we find out more, we’ll post something. This problem may be something to do with Lightroom, Mac OS X components, Quicktime Player or, erm, user error. More to come on this if we get something interesting for you.
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September 3rd, 2010 by Bahi