The Preview Scaling setting may be used to reduce the resolution of video processing when you are using a fair amount of filters, transitions, and track blending. This may help with the performance during the editing process.
However, keep in mind that the source video or images must typically be scaled down to the designed preview scale, and that will have a processing cost. See Settings > Proxy Editing for the remedy to that. Proxy generates substitute clips at the same resolution as preview scale to eliminate the overhead of this scaling.
The submenu lists only the vertical resolution. The horizontal resolution depends on the aspect ratio of your project.
- 360p is a good choice on a 1080p screen or less
- 540p is good choice when working on a high density screen or screen with resolution > 1080
- 720p is a good choice when working on a 4K screen or with 4K UHD footage and you want to get a
little more clarity
Preview Scaling was added in version 20.02.
Export
Export > Advanced > Video has the option Use preview scaling.
This is intended to provide a faster export for draft review. You should leave the export resolution set to the project resolution unless your preset or video codec dictates a resolution.
Caveats
- The Stabilize video filter disables preview scaling for the clip on which it is applied because it is incompatible.
- Preview scaling is a step further away from WYSIWYG (what you see is what you get) and does not provide perfect fidelity and full precision. Some differences are unavoidable especially where blur, softness, and noise are concerned.