THE SHORT ANSWER
Here's the approach.
Create proxies with Transcode Media. In the 10.8 guide, Apple lists ProRes 422 Proxy and H.264 as proxy formats, with selectable frame sizes. Proxy media provides a lighter editing representation while the original files remain available.
Creating proxies and choosing them for playback are separate actions. Before sharing the finished project, switch the viewer back to Optimized/Original so the export uses the higher-quality media.
Related tutorial.
Full tutorialThis is a supplemental tutorial. Its compatibility with Final Cut Pro 10.8 has not been confirmed. Use the written steps and version-specific sources for the controls.
By Ripple Training. YouTube oEmbed confirmed the title, creator and thumbnail. The software version shown in this video has not been verified. No watched-content review, answer timestamps, transcript, duration or upload date is asserted. Playback was not tested.
WORKFLOW OVERVIEW
Conceptual proxy workflow
Original media
Keep the full-quality source files available.
Create proxies
Transcode smaller editing representations.
Edit with proxies
Choose proxy playback in the viewer.
Return for export
Choose Optimized/Original before sharing.
A conceptual workflow illustration. Follow the version-specific steps below for the actual controls.
Step by step.
Final Cut Pro 10.8- 01
Select the source clips
Select the clips or projects in the browser and choose File > Transcode Media.
- 02
Choose the proxy settings
Enable Create proxy media, choose a format and frame size, then click OK. Monitor progress in Background Tasks.
- 03
Choose playback media
Use the View menu at the top right of the viewer to choose proxy playback after transcoding finishes.
- 04
Prepare the final export
Choose Optimized/Original in the viewer before sharing the finished project.
Sources & version notes
Written for Final Cut Pro 10.8. Menu names and available features can differ in other versions.
Version reference: Final Cut Pro 10.8Written answer checked against the linked official documentation for Final Cut Pro 10.8. Related videos have metadata verification only; they are supplemental resources, with no verified answer-specific timestamps or software-version compatibility assertion.