On Wed, Sep 8, 2010 at 10:40 AM, Alan McKinnon <[email protected]> wrote: > Which raises another layer of confusion: when a spec says "16:9" does it mean > physical dimensions, or pixel density? I've yet to find a device that clearly > states *how* it arrived at the numbers it quotes in it's spec.
I think DPI is irrelevant in the aspect ratio calculations. The aspect ratio only describes the relationship between the width and the height of the display. AFAIK all LCD TV and monitors have pixels which are 1x1 size, so the aspect ratio should apply both to the physical dimensions of the screen as well as the pixel count. Basically, divide width/height or X/Y pixels and you will get the aspect ratio for an LCD monitor/TV. For example, my monitor is an obviously clear mathematical case, the screen is exactly 16" wide and 12" high and has a resolution of 1600x1200. Both 16/12 and 1600/1200 can be reduced to 4/3, or 4:3 (also referred to as 1.33 aspect ratio). 16:9 is 1.78, and 16:10 is 1.60. When you get into source media, things can get crazy, as the pixel aspect ratios are all over the place. Even with HD the source media is not always 1:1 pixel aspect ratio, for example HDV cameras use a 1440x1080 image resolution for 1080i recording, which is a 4:3 pixel aspect ratio but 16:9 frame aspect ratio. In other words, in this mode each pixel is 1.33 times as wide as it is tall. Old (pre-HD) televisions, CRT monitors, PAL vs NTSC, DVD, anamorphic widescreen, etc. It's all a bit of a mess. They've really eliminated that headache with HDTV and LCD displays for the most part. (I'm using the term LCD generically to also include other LCD-like technology such as plasma etc.)
