HD Naming Conventions?

golf4life80

At this point I feel I am pretty well versed in things HD pertaining to aspect ratio, resolution etc. But I feel as if I'm missing something related to why things are called what they are.

I'll form my question around 720, but it pertains to 1080 as well.

The way I understand it, 720p is 1280x720 pixels when in 16:9 aspect ratio. The 720 counts the horizonal lines of the picture (or could be called the vertical pixels). BUT, say when a movie is filmed in 2.35:1 aspect ratio, the resolution is more like 1280x544, Same goes for 2.40:1 which would be about 1280x534.

Yet these are both still considered "720p". So why call it by that name?? It seems the common number is actually 1280. Why not use that instead?

There's got to be some reason here or something I'm missing.

rbinck

Basically since the beginning of TV time TVs have been rated by the number of lines they will display. While the width could be a better measure as you stated, legacy says to use the lines. 720p applies only to the TV and the signals, not the source. Whatever is sending the signal to the TV that has the letterbox video is still sending 720 lines of video, just some of them are black.

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Scottnot

At the point where you wrote, "BUT, say when a movie is filmed . . . " you sort of changed the subject of your question.
How content is produced has nothing to do with specifying the resolution of the display.

The television display is 1280x720; the number of pixels is fixed and can't be changed. That's why it's called 720.

Some content will not fill the entire screen; some will not fill the screen horizontally; some will not fill the screen vertically; some will not fill the screen in either horizontal or vertical. But no matter what the content, the physical display will always be 1280x720.

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golf4life80

I guess this was pretty much the answer I was expecting. It's just the way it is.

golf4life80

Maybe I worded the question a little bit wrong. I understand what you are saying about the display, and why there are bars etc. I was refering to when content is actually labled as 720p or 1080p, but with the aspect ratio greater than 1.78:1.

I just thought it was odd that everything was labeled with the number of horizontal lines, but thats just the way it is I guess.

1080PsF

Video has always been based in scan lines and I think that is because there were no horizontal pixels before digital, but there always have been horizontal scan lines.
NTSC is 525 and PAL is 625. Now HD is either 720 or 1080 and the part I think is strange is that we no longer include the vertical blanking in the numbering. When HD started it was 1035 and then came along 1080 so I think it was just to help us know what type of HD it was because they are both 1125 including the vertical blanking.

The picture is made up of active picture info and horizontal and vertical blanking. The active video is the picture that you see and the H&V blanking are to synchronize the picture.