… for Codecs & Media
Tip #1158: File Size is NOT Image Quality
How long is a piece of string? Don’t focus on file size, focus on image quality.
During a recent webinar, Lane asked:
I’m creating a program of Christmas carols that may run about 30 minutes. I’m concerned about the file size because, when compressed, this program will likely give me a huge file. What should I do to keep file size down?
All too often, editors obsess about the size of their compressed file. This is the wrong thing to worry about.
File size is determined by two factors: bit rate and the duration of the movie. Longer programs will, by definition, have larger file sizes. There’s just more movie than in something shorter.
Instead, we need to focus on image quality. This is a combination of six factors:
- The codec you are using
- The frame size of the compressed file
- The frame rate of the compressed file
- The amount of movement between frames
- Whether the movie is for streaming, download or posting to social media
- The bit rate at which you compressed it
In general, for a 1080p movie, assume a ROUGH compressed file size of 20 MB/running minute. For a UHD file, assuming 60 MB/running minute. Both of these use the H.264 codec, which I recommend instead of HEVC.
These are rough guides, but any longer program is going the create some really large files.