aspect ratio- beginner question

T

tmp309

Member
Hopefully this won't be too silly a question:

We shot some footage w/ the DVX100a in 24p, and when I captured the video into FCP, it came in as 720x480. Looks fine. But when I export it using the same settings, or open up any of the capture files in Quicktime, or open them in After Effects, the picture is stretched horizontally. If I export it with the NTSC 4:3 settings (640x480) it looks correct again.

If anyone can help a beginner out, what is going on?

Thanks so much.
 
yeah i noticed that too. My import and timeline settings are 720x480. The video says it is 720x480. But it is actually 640x480. Is it recording this size, or getting chopped at some point? What's the deal?
 
This is a big concern because aren't DVDs 720x480? So if I'm recording DVX footage 640x480, then it'll have to be digitally scaled and lose quality for DVD! I know there is probably some obvious solution to this, but I had to send in a rebate form for Barry's book and it isn't here yet! AGHHH help!
 
DerrickTempleton said:
This is a big concern because aren't DVDs 720x480? So if I'm recording DVX footage 640x480, then it'll have to be digitally scaled and lose quality for DVD! I know there is probably some obvious solution to this, but I had to send in a rebate form for Barry's book and it isn't here yet! AGHHH help!
Click to expand...

They shouldn't be..... should be the resolution of NTSC TV (for NTSC DVDs.)...

640 x 480

If you take 4:3 (SD Aspect ratio) and divide 4 by 3, you get 1.3 repeating.

720 divided by 480 is 1.5

640 divided by 480 is 1.3 repeating.
 
ah yes that makes sense...on my old sony handycam that shot 720x480 the sides were always cut off on a tv anyway. So DVX does in fact record at 640x480? I was confused because all the presets in FCP, Compressor, DVD Studio Pro are for 720x480.
 
DerrickTempleton said:
ah yes that makes sense...on my old sony handycam that shot 720x480 the sides were always cut off on a tv anyway. So DVX does in fact record at 640x480? I was confused because all the presets in FCP, Compressor, DVD Studio Pro are for 720x480.
Click to expand...

Yes, very roughly.... it's slightly higher than 640 by 480, cause it's marketed as 310,000 active pixels..... 640 x 480 is 307,200.
Could just be rounded up though.

but 720 x 480 is 345,600.


I think the Native Pixel count is 380,000; which would be 720-ish by 525-ish, but that just the size of the sensor not the Active pixels.
 
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Well you're ignoring Pixel aspect ratios; the pixels arent square, they're actually 9/10 wide what they are tall when shooting in 4:3, and 12/10 wide when shooting widescreen.

4:3
720*.9 = 648
648/486 = 1.33333

16:9
720*1.2 = 864
864/486 = 1.7777777 or 16:9

Why it appears streched is because when you play the file in something other than FCP, it displays the pixels as square, even though they shouldn't be.

The reason why when you export at 640*480 it looks ok is because at a square pixel format, it displays correctly, as 640/480 = 1.33333, and a computer monitor is a square pixel format.
 
ALove said:
Well you're ignoring Pixel aspect ratios; the pixels arent square, they're actually 9/10 wide what they are tall when shooting in 4:3, and 12/10 wide when shooting widescreen.

4:3
720*.9 = 648
648/486 = 1.33333

16:9
720*1.2 = 864
864/486 = 1.7777777 or 16:9

Why it appears streched is because when you play the file in something other than FCP, it displays the pixels as square, even though they shouldn't be.

The reason why when you export at 640*480 it looks ok is because at a square pixel format, it displays correctly, as 640/480 = 1.33333, and a computer monitor is a square pixel format.
Click to expand...

Very true, forgot about that, the pixels that is, my mistake......
 
yes...so many things to keep in mind. Well I think I get it now, hopefully be able to keep track. They taught this stuff to me in school but I usually skipped lecture classes so I could actually film my movies instead! Who'd a thought it was actually useful lecture!
 
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