Question : why add this LPP step instead of matching the bluray to the 70mm for the first frame ?
The goal was to regrade the Owen/C-3PO frame. The assumption of the method is, that the degradation of the colors of these shots is very similar for the LPP independent of the shot. Therefore, the correction for one shot should still be pretty accurate for another shot, and can therefore be transfered to another shot. Since, the bluray was regraded on a shot by shot basis, the regrade for one shot cannot be transfered to another shot.