-
Aspect Ratio Differences
I’ve encountered some strange behavior with Quicktime’s aspect ratio. While projecting my film at a film festival on Digibeta, I got a comment from a projectionist that my images look slightly “fat”. My film was originally shot in NTSC SD DV format using the DVX-100, so the aspect ratio is 720×480. While doing color correction the post house recommended using 10 bit material to better handle titles, and that’s when I discovered that 10 bit aspect ratio is 720×486. So I wondered whether that might be the cause, although going from 720×480 to 720×486 would make the images look thinner not fatter. So I just did a quick test, opening a 10 bit Quicktime self-contained movie and this is the image:
But when I drop this into an FCP sequence the image looks “normal”:
I was wondering why the aspect ratio for Quicktime would look different. I guess I don’t need to worry so much because the images seem fine, but I don’t really have a Digibeta deck to double check and see what the problem is. Any info would be much appreciated!
Thanks.
-
16 Replies
-
Once more for luck then Alexander ….
The difference is apparent because of the non-square Pixel Aspect Ratio of your encoded video … by default Quicktime is displaying your video using a square pixel ie using it’s Clean Aperture setting, but you want it to display using the Production Aperture instead (this mode compensates for pixel aspect ratio and is the default display mode that FCP uses).
You can change that in Quicktime Player by modifying the clip’s Conform aperture to: setting in the clip’s Movie Properties window. Step by step here:
https://support.apple.com/kb/TA24215?viewlocale=en_USBest
Andy -
As well, when they transferred your footage to 720×486, it should have in no way been elongated. The process should add black lines to the top and bottom to fill out the extra 6 lines.
-
h Andy,
I don’t see that very clear.
Normally QT display Square pixels so make faces more elongated, Greco like. The typical post of “I exported Anamorphic but my QT movie now is 4×3′.
Also you said that FC by default uses “production aperture”.
Up to the link that you added: “Production aperture scales according to the pixel aspect ratio but does not crop the video”.
But in the FC picture (lower) there is a big cropping on top of the head of the boy.For me in the upper picture the boy may look a bit “fat”, but in the lower picture think that looks too much elongated for a kid.
rafael -
Thats a good catch Rafa.
What we’re missing are some more details as its hard to know quite what we are looking at with these screen shots, like how and where they were captured …. we know that they visually describe the problem but we don’t know quite what they contain eg are those letterbox bars or is it just the capture background? if they are they letterbox bars then are they part of the original source / master? was the footage shot full frame 4:3, letterboxed 16:9 or anamorphic 16:9? where are the screen captures coming from ? (the loss of headroom in the FCP image is conducive with a clean aperture representation of a 10 bit uncompressed image).
On reflection, the upper image looks like a letterboxed 16:9 clip thats been incorrectly given a 16:9 display size (ie its a letterbox 16:9 that is displaying with an anamorphic stretch).
-
720×480 or 720×486 are not aspect ratios. Those are resolutions, and either one will display the same if it’s being shown right.
Your aspect ratio is either 4×3, aka 1.33 or 16×9, aka 1.78. In standard def, 3×4 and 16×9 have the same resolution, 720×480 or 486. IOW they use the same number of pixels regardless of the aspect ratio.
Your FCP manual explains this in some detail, so if you want a better explanation, I’d refer you there.
the difference between 480 and 486 is irrelevant to this problem. It’s purely a mistake in how the file was setup & flagged on your DVD or Quicktime movie.
Arnie
Post production is not an afterthought!
https://www.arniepix.com/ -
[Arnie Schlissel] “Your aspect ratio is either 4×3, aka 1.33 or 16×9, aka 1.78”
4×3 1.33 is full frame. You can still have 4×3 1.78, 4×3 2.35, 4×3 2.40, etc.
Likewise you can have 16×9 1.78, 16×9 2.35, etc.Not arguing but just don’t want people to think that all 4×3 is 1.33 and all 16×9 is 1.78
Joey
-
[Joey Burnham] “4×3 1.33 is full frame. You can still have 4×3 1.78, 4×3 2.35, 4×3 2.40, etc.
Likewise you can have 16×9 1.78, 16×9 2.35, etc. “You’re confusing the issue. SD video can only be 4×3 or 16×9. Don’t ask me, ask SMPTE.
The image inside of it can be letterboxed to be anything you want, but the shape of the video itself can only be those two aspect ratios.
Judging by Alexander’s screenshots in his original post, his video may be letterboxed inside a 3×4 video. Or maybe not. It’s hard to tell from just one screenshot.
Arnie
Post production is not an afterthought!
https://www.arniepix.com/ -
Sorry I didn’t mean to confuse the issue. I just thought it should be noted that by stating that the above stills are 4×3 1.33 is misinformation. As you said, they could be letterboxed 16×9 footage, or any flavor of SD 4×3.
Joey -
Sorry I was out of the loop, just checked my e-mail…
Anyway, the film was shot 4×3, but my editor decided that adding a 1:66 matte would give it a more “filmic” look. No anamorphic and no 16×9 used.
Rafael, I think the kid’s head is actually that long :-p
-
Hey again Alexander
When you open this file in Quicktime Player and press Cmd-J to open the Movie Properties window, what is the Display Size and Normal Size as noted in the Video Track’s Visual Settings tab? If they differ then uncheck “Preserve Aspect Ratio” and set the Scaled Size to the same settings as given for the Normal Size.
That should bring your files display size back to where it should be.Best
Andy
Reply to this Discussion! Login or Sign Up