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Why is the camera at 702 and not 720?
I have been running some test with my HVX for 3D camera tracking. When I bring the footage into Shake it is compressed to 960 so I first open it in Quicktime and export out a 1280 x 720 HD version.
When I select the in information box in QT it tells me the size of the files are 1248 x 702. I thought the camera shot at 1280 x 720? The smaller size is still 16:9 but smaller.
Why is this? Does the camera not shoot at 720 but 702?
Thanks,
-Lars
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11 Replies
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WHy not work on it at the native frame size of 960×720?
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If I do a 3D track with the image compressed like that then I need to work with it compressed in Cinema 4D. I would have to render out all of my CG models compresssed and then try to expand them later to 1280 x 720. It is easyer for me to see the CG over a correct looking plate. that is why I bring it into QT and export out a version that is 1280 x 720 to start with. After that part it goes into Apples shake to apply Lenswarp node to undistort the image for a better track. hard to see what is happening at 960 x 720.
I’m just wondering why the file wants to be 1248 x 702 instead of 1280 x 720
-Lars
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If you do this- switch out of the DVCPROHD codec into say 8-bit uncompressed. DVCPROHD likes certain frame sizes and is probably causing this issue. Or use an image sequence- better for heavy VFX work.
Noah
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That is what I have been doing, I switch up to a codec called Microcosm. In QT under the export options in the size I select HD 1280 setting and not the current. So will that be streching the image? If the native size is 1248 x 702 I would be streching the image to 1280 x 720.
Thanks for the help in understanding why it is not a 720 image.
-Lars
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First, it sounds like a quicktime reporting error to me, just like quicktime has a tough time telling you the real frame rate. If you exported it 1280×720, I’m sure it is 1280×720 it’s just that quicktime is broken somewhere in it’s reporting capabilities.
Second, I still don’t know why you need to re-export the movie. If I were you and wanted to work at 720 resolution, I’d take in my native DVCPRO HD clips, and then change the aspect ratio to square (I know this is possible in After Effects and I’m sure Shake has something similar) and then I would start my compositing. Changing the frame size and putting the footage though and unnecessary round of compression is, well, unnecessary.
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I’d be very surprised if it didn’t have something to do with microcosm. Seriously use a TIF or TGA sequence- that is what all VFX houses work with to avoid this sort of issue.
Noah
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An image seq. might be the best way. I never thought that QT would be reading it wrong but you might be right about that. Apples shake seems to think it is 1280 x 720 and when I make an aspect adjustment in that porgram then it works fine to.
Thanks for your help!
-Lars
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[Noah Kadner] “I’d be very surprised if it didn’t have something to do with microcosm.”
You could be right, Noah, but I think it’s just a quicktime error. It’s just like frame rate. When you play a movie back in quicktime, it never reports the correct frame rate. It’ll always give you something weird and non standard and it also does this for the aspect ratio of some movies as well. It will attempt to show you a square pixel movie from a non square pixel source and it’ll report the wrong frame size. As long as everything is lining up in Shake, I wouldn’t worry about quicktime.
Jeremy
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Right- this sort of hassle is precisely why you’ll rarely see an .MOV or AVI used in VFX production houses. Also because if a 3D render fails in mid render all frames are lost to a QuickTime output but if you’re rendering frames you lose one frame and you can restart the render from that point on.
Noah
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This is an insidious new feature in QT 7.1 I think having to do with the “presentation aperture” being a 10% crop. When I run QT Pro for Windows on a DVCPROHD movie for example, (using the Raylight decoder) I can see the setting in the movie track properties, “Presentation” tab. Fortunately it can be turned off.
Why did they do this? I really wish someone in the know at Apple could respond here and explain it. From the other responses here it’s obvious that No One Was Informed.
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