Q: I’m currently adding album art images to my MP3 files via iTunes. I was wondering whether there is an ideal width and height that would enhance their appearance in the iPod photo and would make them look sharper while minimizing “pixel distortion.” Is 170×170 pixels OK?
A: There are two answers to your question. The easier answer is to use high-resolution artwork and let iTunes handle the sampling for you, and this would be our recommendation. We tried one set each of practical and theoretical tests with the iPod photo’s screen, and found that in our practical tests with an actual piece of album artwork, the differences between iPod album art downsampled from various resolutions were barely if at all noticeable.
However, when you sync your files to your iPod, iTunes downsamples album art to 140×140 pixels for full-screen display, and 56×56 pixels for the thumbnail view (the one that displays with the name of the track and other information). If you want to optimize your artwork for one of these views, choose the appropriate size. For example, if you add 140×140 pixel album art in iTunes, it will appear with no subsequent distortion on the iPod photo when you display it full-sized. However, you will have some distortion when you view it in iTunes, as iTunes has to resample it to display at 200×200 pixels.
If you’d like to try and see exactly what the results are, here are two graphics: this one is a 140×140 pixel pattern, and this one is a 280×280 pixel pattern (which we used to check the 1/4 downsampling). You’ll notice that the 280×280 image looks better in iTunes, but the dots look like flat gray on your iPod photo, whereas the 140×140’s dots display identically on iTunes and the iPod.