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Confused on FARs, PARs, and Pixels

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Eric HartmannConfused on FARs, PARs, and Pixels
by on Jan 14, 2011 at 2:29:48 pm

I have video captured from a SD DV camera.

When I bring it into Premiere, it sees it as 720 x 480 (.91). When I bring it into After Effects it sees it the same way.

When I look at the video in Quicktime, it appears on my computer as 640 x 480 (I screen shot it and sized it in Photoshop). This is confusing to me, but it looks fine to my eye. Is this resizing of the frame aspect ratio, maybe to deal with viewing the non square pixel on the square pixel monitor?

When I launch a NTSC DV sequence in Premiere, it has the following specs: 720 x 480 (.91) 4:3. When I put the video into the sequence it looks fine, just like the Quicktime. When I export the video, it looks fine, just like the Quicktime. This works like I expect. I am pretty sure this is how things work in Final Cut Pro, the system I am most familiar with.

When I launch a NTSC DV sequence in After Effects, it has the following specs: 720 x 480 (.91) 3:2. When I put the video into the composition it looks fat, stretched compared to the Quicktime. When I export the video, it looks fat again, stretched compared to the Quicktime. This is confusing the hell out of me.

What am I missing? Why do the programs define NTSC DV differently? And what is the aspect ratio of NTSC exactly, 4:3 or 3:2? 640 x 480 technically seems like it is 4:3 and 720 x 480 technically seems like it is 3:2, but I have always heard 720 x 480 referred to as 4:3. I always assumed that the non square pixel that a factor in this, but I don't know for sure, and After Effects has me completely confused.

Please help!!


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Michael SzalapskiRe: Confused on FARs, PARs, and Pixels
by on Jan 14, 2011 at 2:42:51 pm

What version of After Effects are you using? Some versions didn't quite read non-square things accurately. This page [link] has a ton of useful info on pixel aspect ratio.

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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Eric HartmannRe: Confused on FARs, PARs, and Pixels
by on Jan 14, 2011 at 2:52:35 pm

I have CS5 open in front of me, but CS3 seemed to operate in the same way when I look at that last night at home.



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Eric HartmannRe: Confused on FARs, PARs, and Pixels
by on Jan 14, 2011 at 3:10:31 pm

I read that link (thanks) and I am still confused.

I understand that what I am seeing in AE as a fat image is likely non-square pixels displayed as square pixels. But why does Quicktime and Premiere handle them differently? And I still don't understand why Premiere calls NTSC DV 4:3 and After Effects calls NTSC DV 3:2.



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Tudor "Ted" JelescuRe: Confused on FARs, PARs, and Pixels
by on Jan 14, 2011 at 3:49:08 pm

720 x 480 is the NTSC DV format with .91 pixel aspect ratio. Thus the frame aspect ratio is 3:2, but with a .91 par.
720 x 540 is NTSC with square pixel aspect ratio, and thus 4:3.
There is also- to confuse you some more- a D1 NTSC standard, which has 486 instead of 480...
The pixel aspect ratio comes into play if you are displaying your video on a tv screen that has pixels that are not square but rectangular. Basically you squeeze the image from the 540 square pixels from your computer image to be correctly displayed by the 480 rectangular pixels on your tv screen.
You just need to make sure that AE interprets your clips correctly. If you have NTSC DV footage you work with, make sure that your Comp in AE is setup for that standard. For correct preview use the toggle par button to see the image displayed at 720x540 (CS5 will say 720x536 for NTSC square pixels... don't worry). When you render, just make sure your output is the size/par NTSC DV. Do this and you should be fine- if something is not right in your final output just check the interpretation for your clips, comp settings and render settings.
Hope it helps.

Tudor "Ted" Jelescu
Senior VFX Artist


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Eric HartmannRe: Confused on FARs, PARs, and Pixels
by on Jan 14, 2011 at 4:09:25 pm

OK, the toggle PAR button is the thing I was missing. I think Premiere and Final Cut Pro does this automatically (at least I never remember having to mess with it). It was messing with my head, lol.

This is the first project where I have been mixing PARs on the same timeline. I was understanding interpreting the footage, but confused when it looked distorted in the window. I see the reasoning for displaying the pixels so they conform to the square PAR of the monitor, though - that way you can do accurate pixel level editing.

Thanks for the toggle tip!



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Dave LaRondeRe: Confused on FARs, PARs, and Pixels
by on Jan 14, 2011 at 4:19:05 pm

[Eric Hartmann] "When I launch a NTSC DV sequence in Premiere, it has the following specs: 720 x 480 (.91) 4:3....
When I launch a NTSC DV sequence in After Effects, it has the following specs: 720 x 480 (.91) 3:2."


It is indeed confusing! I'm not sure who's responsible for the confusion, but rest assured they're both 4x3. It's just that the second one above does NOT describe the screen aspect ratio -- it's the ratio of the pixels on the screen. Do the arithmetic and you'll see what I mean.

So why do they do that? I have abso-flippin'-lutely no clue. It's one of those things that must be learned and endured, and it really stinks on ice.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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