A camera file can look excellent and still be awkward to edit on a particular machine. If playback hesitates while choosing shots, the editor may struggle to judge a cut. That does not automatically mean the footage needs to be replaced or the entire project converted.
Start with a short, repeatable section containing the problem. Note what is slow: starting playback, moving between frames or running a shot with effects. Let unrelated background work finish before comparing changes. Otherwise the test may be measuring two different workloads.
A proxy is a lighter editing copy associated with the original clip. It can make demanding footage easier to decode while leaving the source available for delivery. The useful question is whether it improves this project on this machine.
The walkthrough for testing a small proxy sample in Lightworks recommends generating a few representative clips first. Selecting a lower playback-quality option does not create the proxy by itself; generation must finish before the comparison means anything.
Check detail against the original
Use the easier playback copy to make timing decisions, then compare the original when judging focus, texture or fine product detail. Keep the camera files protected and available. A small proxy should not quietly become the only surviving copy of the shoot.
Lightworks Guide’s practical tutorials explain the related media and export checks. Before a client delivery, confirm that every required original is online and inspect the completed local file. If the sample does not improve the observed slowdown, investigate storage, effects or competing tasks rather than processing all remaining footage on assumption.