I received an email today asking this:
I read a post you wrote back in 2013 and I can’t find anything on my question.So I decided I want to use this to speed up my editing since it gets choppy on playback making it very hard to edit. I would like to know what is the difference in optimized and proxy? Why should I transcode to both or one of them? I have a feeling proxy is the best for quicker transcode and smaller file size. But why would you transcode to optimized or both? Thanks.
Proxy is a quarter resolution ProRes Proxy version of your clips, and not only is the number of pixels reduced by 1/4 but because of the ProRes Proxy codec, the space needed and bandwidth is reduced by another 1/3. The result is that it takes 1/7 the bandwidth and size. This means that for for footage on a codec like Canon h264 1080p material, ProRes Proxy is even significantly smaller.
Canon 1080p h264 on the left, FCPX Proxy on the right.
Proxy also switches Final Cut Pro X into1/4 resolution, so playback, rendering and sharing/export are all at 1/4 resolution. This is the big gotcha with Proxy as you need to be aware of it when exporting as it will render at 1/4 resolution, although it will still export at the pixel size chosen when you share.
Personally I use Proxy when I’m working on multicam with more than 3 angles. Instead of struggling to playback, it just flies in Proxy. I also have some older iMacs that I reserve for assistant editors or sound cleanup and transcoding to proxy lowers the CPU usage for that older Mac and also lets us have multiple streams over our gigabit ethernet network.
I hope this helps!