Towards the end of 2008, YouTube announced a change to the aspect ratio of the default player for the site. The standard ratio for online video had been 4:3, but the new player standard is now 16:9. Aspect ratio is simply an expression of the relationship of height to width. Something that is 4 to 3 might be 4 inches wide and 3 inches high, and if it is shown on a screen that is 40 inches wide it will be 30 inches high.
Google opted for the new 16:9 format because it had become the universal standard for HDTV and the ensuing onslaught of wide screen HD monitors. As it turns out, most large plasma TVs and even smaller personal viewing devices such as laptops, iPads, and smart phones are set-up to view the 16:9 ratio more fully than the older standard. The standard computer monitor used the 800 x 600 (or 4:3) ratio but most laptops use the 1280 x 720 (or 16:9) resolution for viewing.
Virtually all modern still and video cameras have the wide screen format as a setting or as the default factory set-up.
Over the last year or so I’ve noticed a trend in the world of presentations. I have been asked on more than one occasion to submit my slides to a conference where I was speaking in the 16:9 format. Larger conferences in particular are finding the wider screen works better in very large rooms and commonly employ supplemental monitors around the room or conference that are often wide plasma screens.