If your source is uncompressed and you keep rendering all effects and grading to uncompressed formats, then you should be fine. The visible loss in quality comes in when you work with compressed footage and then render out compressing again. So if you have a compressed source that you need to work on, convert that to an uncompressed format, apply effects and grading, render out to uncompressed and then use a compression software (like Adobe Media Converter) to compress to a delivery format.
Tudor "Ted" Jelescu
Senior Compositor/VFX Artist
To add to Ted's point, try to minimize the number of generations through your workflow, especially if you're using 8-bit video files, as they can accumulate rounding errors. For example, if you need to change a color grade, go back to the original grade and adjust it. Don't start a new grade with an already-graded clip as the source.
A smart workflow and lossless intermediates will keep your quality high.
Principal & Designer at Keen Live
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