With the new iPhone and iPod Touch, Apple has been promoting the new screen with a higher resolution, and gave it a fancy name “Retina Display”
With an increase of resolution from 480 x 320 for the previous models to now 960 x 640 you would expect a drastic improvement in terms of video playback, however there are some pitfals.
Over the last week or so, I have been doing some tests on my new iPod Touch (8GB model), and here are my findings. (this applies to the iPhone 4 as well)
The physical size of the screen is identical to the previous generation. Even though the resolution has doubled in both width and height, the physical area used to display them is identical, meaning, the individual pixels just got a lot smaller. Most people, including myself, are aware of the fact that if you increase the resolution, you gain screen estate. Icons and text becomes smaller, so you can fit more on the screen at the same time. For this reason alone, I use a laptop with a 1920×1200 screen resolution for development and daily use.
Apple’s approach with the Retina display is different. Rather than using the increased screen resolution for displaying more on screen at once, it leaves everything at the same physical size, but uses more pixels to display everything. The home-screen icons are physically the same size, but are actually made up from 4x as many pixels. Fonts are the same physical size as the previous generation, but again, they are made up from more pixels, giving it a cleaner look.
To be honest, when I unpacked the new iPod Touch 4, I was expecting a tiny iPad. With a screen resolution (960 x 640) so close to the iPad resolution (1024×768) I was hoping for more screen estate, but nothing was further from the truth. Fortunately, my initial disappointment was eliminated the moment I ran a few of my favorite apps. Especially Stanza (a free iBooks-like eReader) as well as Safari greatly benefit from the Retina display. Comparing an eBook on the 3G iPod Touch and the new 4G one showed a world of difference. On the old one you could clearly see that characters were made up from individual dots, but on the new one, this was not noticable at all. Doing some reasing resulted into a much greater and satisfying experience.
So, after my successful reading test, of course I had to test video as well.
I used DVD Catalyst 4 (beta) to convert a HD (1080) movie trailer, and set the black-bar removal option (global settings > borders) to “remove from device”. For settings, I used the standard iPod Touch settings at a quality of 600 Kbps with the default 480×320 screen resolution, and for the new one, I used 2400 Kbps. (with the higher resolution, the amount of pixels is actually 4x as many, so by increasing the bitrate to 4x as much, the files are theoretically identical in quality. Each individual pixel gets the same amount of bits to determine the quality)
With playback on the iPod Touch 4G, I was expecting to get a different result, especially with the file-size increase.
Screenshot from the iPod Touch 4 playing a full-screen 480 x 320 file.
Screenshot from the same position on the trailer encoded at 960×480 resolution
While the screenshots might look identical, have a look at the forehead of the guy on the left (sorry, I am not into Twilight, so I don’t know his name). You will notice the wrinkles are slightly more prominent in the 960×640 file.
While there are differences noticeable, note that these are screen shots. The video itself runs at 30 frames per second AND because you are not looking at the shots on a retina display, the pictures are larger in size than what you would actually use to view them on.
cutting the resolution in half will present you with a size similar to what you would have when you view it on your iPhone 4/iPod Touch 4. Now, it is even harder to tell the difference between the two.
The above conversions used for creating the screenshots were done using a 1080 HD trailer. If you use lower-resolution content such as video files or even DVDs, the difference is even less obvious. The original HD video file used has a resolution of 1920 x 800, which is on both width and hieght larger than the resolution of the Retina display. A DVD generally has a resolution of 848×480, which means that the video itself has a resolution that does not match the retina display resolution, so it will be upscaled in a similar way as the 480×320 video file. While slightly sharper, it will not even come close to the quality of an HD file.
Conclusion:
Unless you use the iPhone 4 or the iPod Touch 4 with a TV dock, or use the files also on a different device, such as the Apple TV or even an XBOX360 for example, I don’t think it justify the 4x larger file size. If you use the files on a TV or large-screen device, you will benefit from the higher resolution of your video files, but the quality is also affected by the resolution of the original video.For my own use, I am going to continue the standard iPod Touch settings rather than filling up my 8GB with 4x larger files that look pretty much identical.
Closing:
I understand that the information in this article goes against unwritten rules in terms of video quality and screen resolution, but the retina display is advertised in a similar way. Rather than just blindly following numbers and specifications, I wrote this article to provide an honest look on how the retina display works with video.
I created an archive with the original screen shot files and the created video files so you can compare them on your iPod Touch 4 or iPhone 4 for yourself and make your own conclusion.
You can download them here:
http://www.tools4movies.com/files/retina.zip
