[Jeremy Garchow].AVC-Intra support is really strange. The lower bandwidth avc-I files take up more room than their optimized ProRes equivalents. This really doesn’t add up for me. A 145mb/sec (ProRes) file should be bigger than a 100mb/sec AVC-I file, but this is not the case.
I can’t say this with any authority yet (kind of new in working with ProRes on any regular basis and waiting to start shooting AVC-I), but I believe that AVC-Intra is a constant bitrate format (i.e. if you are shooting the full AVC-I 100 it will be 100mb/sec constantly), whereas ProRes seems to be a variable bitrate (I’ve noticed that the bitrate seems to change while encoding).
I believe this might explain the difference in size.