How to best use different resolution camera and final render footage

[John Br]

Hello,

I am working with a chroma key setup and using external photos.

In order to get the most data I can for better keys I am recording at 4k, the best I have available to me, but I am rendering in 1080p. In order to get the most from my 4k footage should I be working in the 1080p timeline that I will render to, or at the native 4k of my footage? I want the 4k data to be available for subsampling, hoping someone knows the best way to do this.

Thanks!

[R Neil Haugen]

If it is placed on a 1080 timeline using "set to frame-size", then Premiere always will do the calculations for any size changes and processing from the original pixel data. If you used "scale to frame-size", then Premiere computes the image at the (in this case) 1080 resolution of the sequence, and all further processing including resizing you set would be calculated from the 1080 image.

So ... using Set to Framesize, you should be fine.

Neil

[Richard M Knight]

Is there any advantage to do the keying with a 4K sequence then placing that sequence into a 1080 timeline and reducing the size there. Will it make the keying edge artifacts smaller?

[R Neil Haugen]

Richard ... I know people who work always to key at the 'higher' size, then nest that into a smaller sequence. And others who normally just work the smaller sequence. There are occasional processing differences between the two.

Sometimes it seems to work better to key first, perhaps it is more "pixel-accurate". But sometimes, in the re-calulation of the image to the smaller size then process the key, a bit more smoothness (?) seems to occur.

What work I've done, I simply keyed at the smaller sequence, and it was fine. However ... I wasn't needing to meet a broadcast QC machine, either. So that should be taken into account. Like most things, testing this media in this situation is wise if there's any critical review it will need to pass at the end.

Neil

[Andy 1968]

If you drop 4K into a 1920 X 1080 timeline you do have the advantage of cropping out portions of the shot with no loss in quality. You can pan and scan as needed. Some people do this even if they don't use a green screen. I use this method myself.

[John Br]

Thanks to all who took the time to reply to this, there are many good tutorials out there about things like "how do I do X" but far fewer on optimizing workflow and getting the most from your footage in post.