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Confusion over pixel aspect ratio and frame size
I had a good understanding of pixel aspect ratio, but I must still be confused.
For NTSC a DVD resolution frame is 720*480 at a ratio of 0.9. This is evidenced by my DV camcorder giving me frames at that resolution. If I bring them into Photoshop with a PAR of 1.0 they look wrong. At 0.9 they look good.
So if I want to create frames that are at a PAR of 1.0, then the resolution needs to be 720*543 (543 = 480/0.9). So I take a photo of a circle and import and crop the picture to 720*480 (PAR 1.0). This I import into Premiere Pro 1.5. The picture looks round but it does not fill the frame. I need to change is scale to about 89% to go end to edge. Strange.
So what resolution is 89% of a 720? Its 640! So why does Premiere want still frames at PAR=1.0 at a resolution of 640?
I have read here and at the Adobe Forums that the proper native resolution is 720*543, but this experiment is confusing me. Any have an idea why a 720*543 PAR=1.0 frame needs to be scaled by 89%?
I have a very large photo slide show job to do, and I want to maximize the resolution but also take it easy on Premiere by prescaling the photos in advance so the render times will be less.
-Skye Sweeney
FLL Freak Productions
https://www.fll-freak.com -
3 Replies
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Your thoughts were on the right mark – once upon a time, you’d have to create a 720 * 540 image in your image editor so that the PAR would look good, make your graphics, then rescale them to 720 * 480, save, & import into Premiere (or what not).
That, happily, is in the past. Two things:
1) in Photoshop (don’t remember which version that this showed up in), you have presets when creating new documents. There’s one for NTSC (0.9 aspect ratio).
2) if you used the preset above, importing the resulting file into Premiere should automatically set it to a 0.9 PAR (you can see this in the project window’s header info when selecting the imported PSD file). If it isn’t, you can still adjust it manually if necessary by right-clicking the file & selecting ‘Interpret Footage’. The subsequent dialog has a dropdown that allows you to override the PAR to conform to 1.0, widescreen, etc.
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Thanks for the reply. Unfortunately, I have several hundred pictures that are all at PAR 1.0. I would rather not convert to 0.9 using Photoshop as I have an automated process using custom software to trim the pictures to my 720*543*1.0 format.
I guess I am looking for the best resolution to input a PAR 1.0 file at. Should it be 720*543, 720*540, or something else.
-Skye Sweeney
FLL Freak Productions
https://www.fll-freak.com -
If you’re using custom software & if it doesn’t allow you to specify rendering out to anything other than a PAR of 1.0, then you’ll want to render out at 720 * 540, and then scale the images back to 720 * 480 prior to importing into Premiere. (Point being you definitely want to import NTSC-sized images into Premiere for maximum efficiency.)
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