Can I downscale a 4K video source during editing?

[한솔252694865ydg]

hello. I was wondering if there is a way to  downscale 4k or 8k video sources in After Effects or Premier Pro editing. When creating a 4K video, I can reduce the lag by using a proxy. However, if i want to output FHD video instead of 4K video, and the video source is 4K video, it will take longer and have lag to edit and render, even if i reduce the composition size to FHD. If i reduce the scale of my footage to make it fit the screen, it will only reduce the visible scale, but the lag will remain when i edit the footage.

Is there a way to downscale source footage to FHD without having to encode it separately and then edit it in real time? I really need it.

[Rick Gerard]

In After Effects and Premiere Pro, you can set the resolution of the Comp/Program panel. I always keep mine set to Auto. If your Comp is 4K and you set the Magnification Ratio to 50%, you will be generating the same HD previews you would if you were working in HD. 

[한솔252694865ydg]

Thank you for your answer. However, when applying video effects to 4k source footage and rendering them, even if I resize the composition to FHD, it takes a lot of lag and longer rendering time than working with FHD sources.

For example, if i create the same 8-second FHD video with a plugin that changes the color with AI, and i create it using an FHD source, it will take 1 minute to render. However, if i create an even FHD composition using a 4k video source, it will take over 4 minutes.

Is there a way around this? Other than rendering a 4K source in FHD and importing it?

[Rick Gerard · Accepted solution]

After Effects always looks at every pixel on every layer when rendering the final output. If your output is HD (FHD), and you want to minimize render time, then you'll need to transcode the original 4K footage to HD. You may not save any time in the long run.

Personally, I'm always looking for the highest quality renders, so my Project settings are always 16-bit or better. My source footage is never an MP4 (8-bit color only) unless that's the only footage available, and I never pre-render anything to anything less than a 10-bit visually lossless intermediate. 

[한솔252694865ydg]

Thank you so much for your kind reply, I was wondering if there was some way to do it that I didn't know about because I couldn't find it, but it turns out the only way is to re-encode it! Thank you.