Hi folks,
As far as I know, very little has been said about this. However, Convergent Design has recently stated that Sony has the A7s HDMI port locked to a gamma curve that is closer to REC 709 than true SLOG-2.
It's true, I have tested this myself and the A7s destroys it's SLOG-2 gamma curve on it's HDMI port.
Here is what happens:
1.) Record a SLOG-2 internal XAVC-S file.
2.) Record via HDMI to any recorder that you have.
3.) Compare both files on a scope...you will see that the SLOG-2 gamma curve has been stretched and "damaged". (compared to internal file's "proper" curve on t