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