Hey guys,

We had an interesting anomaly that wasn't an anomaly at all but I felt it was worth noting to the rest of the world. This may be mostly common knowledge but it stumped us for a couple weeks.

Symptoms: File sizes were varying dramatically for reasons beyond our observable understandings. Some of them were 2.5GB, others were 5.5GB

Facts: Every recording was 1280x720x30 at 25MBPS. Every recording was roughly 45-52 minutes in length.

Cause: Video motion was to blame, but not in the intuitive way. The large files had mostly static camera views, while the dynamic camera tracking produced substantially smaller file sizes.

Conclusion: If you have a bandwidth cap of say 5 gigs a week to a service like Vimeo, zoom in and tell them to move! (Or dumb down the bitrate in the recording settings if you know your subject is parked for a while :)

Hope this provides some answers to someone else querying the same issue!

Mike

The mystery of the file size discrepancy is solved.

We ran a test that is repeatable and verifiable: we shot two 1 minute test clips, the first was a static shot with zero movement, and the other had 100% movement (panning left to right, back and forth). The static shot was 3 times larger than the panning shot.

I'm taking a guess here, but my assumption is that with each static frame there is more information and less than can be color grouped in compression because the lines are sharper. We shoot through a 150-500mm lens at about 40 feet, so tracking our target on stage produces a lot of motion blur for the background, which becomes very easy to compress since all the lines and colors are blurred already.

I may be wrong on that guess, but I'm willing to bet that the answer is along those lines in some capacity. I encourage you to try it and compare your results.