As I recently found with my FS100 Macs really seem to hurt your AVCHD footage from Sony cameras and the Panasonic GH2… But especially the Sony FS100.
It is no wonder these cameras often get a bad reputation for limited dynamic range, crushed shadows and blown highlights – when you are only seeing the middle part of the full 8bit range of luma.
This Rec.709 portion of a 601 space (16-235 instead of the full 0-255 the FS100 shoots in) is incorrectly remapped to 0-255 by Quicktime. Therefore apps that use Quicktime at their core like Premiere, trip up. This makes a huge difference to the image. When fixed, you recover over 10% of your dynamic range, highlight and shadow detail, along with a much smoother roll off to whites and blacks.