Ars was recently able to conclude that the newly launched iTunes movies encoded in 1080p do, in fact, look better than the same content encoded in 720p, despite the modest increase in file size. That's good news for iTunes customers. But the real question is: how do iTunes 1080p downloads compare to the reigning king of home video image quality—Blu-ray Disc (BRD)? This is what we set out to test.

Due to hardware and DRM limitations, we were forced to take photos of the screen instead of using screenshots. The screen was the same in both cases: a Dell U2312HM monitor with 1920x1080 resolution, with a MacBook Air connected through the DisplayPort port, and a Panasonic DMP-BD65 Blu-ray player connected using an HDMI-to-DVI cable.

I used the movie 30 Days of Night for the test. According to the Internet Movie Database, this 2007 movie was filmed in the common Super 35 (film) format and then transferred to a 2k digital intermediate; in other words, it was edited in the digital domain.

The iTunes download clocks in at a handsome 3.62GB (where 1GB = 2^30 bytes). It contains a stereo AAC track as well as a Dolby Digital 5.1 track. The video resolution is 1920x798. The BRD is a dual layer BD 50 and has a Dolby Digital 5.1 as well as a DTS-HD track, a number of special features and 30 seconds worth of unskippable copyright warnings.

Things started out well for iTunes with the movie's titles, which look very sharp on both BRD and iTunes 1080p. The images below show the individual pixels. The iTunes image is always on top or to the left, the BRD image on the bottom or to the right.

An early scene that shows a ship on the ice-filled sea also shows that iTunes 1080p almost matches Blu-ray's level of detail. At the top is a screenshot from the MacBook Air, where one pixel on your screen is one pixel from the original image. Below to the left is the iTunes version photographed from the screen, to the right is the BRD version.

Being a vampire movie that plays in (a fictionalized) Barrow, Alaska during the 30 days in the middle of winter when the sun doesn't rise, this movie isn't exactly filled with strong colors. But when they appear, both the iTunes and BRD versions show them off with equal gusto.

As you can see, these aren't your soulful, brooding vampires. Pay attention to the detail on the bright parts of the nose and the forehead. The BRD retains detail while the iTunes version blows them out.

An example of iTunes struggling a bit is this scene where the camera tracks a moving car. The Blu-ray version of the telephone pole close-up shows much more detail—including noise or grain. The trouble with noise is that it's random so it doesn't compress well. This means the stronger iTunes compression needs to get rid of both detail and noise—which are the same thing to a compression algorithm—to hit its compression target. The BRD, on the other hand, can happily reproduce the noise as present in the source, burning up untold megabits and leaving details untouched.

So far, iTunes has been able to keep up with Blu-ray for the most part. But early in the movie, there is a fade from black to dark clouds. Dark gradients are often a problem area with image compression. So it's no surprise that iTunes stumbles at this point, and shows significant banding. Blu-ray, on the other hand, has no problems. (I made the image brighter because otherwise it would be hard to make out on a white page.)

What can we conclude from this?

I was surprised to see how close the iTunes 1080p download comes to Blu-ray, considering that it's only a fraction of the file size. And let's be honest: there are lots of Blu-ray titles that look much worse than this iTunes download. But despite an impressive effort by Apple, Blu-ray still reigns king when it comes to image quality. And unlike iTunes titles, BRDs can have uncompressed multi-channel audio, multiple audio language options, and special features. Am I being greedy in wanting both good-looking downloads for convenience, as well as buy-once-play-anywhere Blu-ray discs of my all-time favorite movies?

Listing image by Photograph by Alan Cleaver