Why is the image brighter after converting H264 to Apple Prores 422 in Compressor ?

Hello -

Very strange situation, keep reading please!

I am using Compressor to convert H264 1080p footage from a D600, to Apple Prores 422HQ for editing. Normal.

I am using the default Quicktime Settings named "Apple Prores 422 (HQ)".

The converted file is a bit brighter than the original... Why is this even possible! 😁 I find this a bit problematic because I'm loosing some details in the whites, at a way too early stage for signal alterationt!

So I tried different other stuff that you will find interesting:

• changing gamma correction in the codec settings had no effect

• I can see the change happening already in the Preview window

• and this is the best one : if I apply a resize, to anything, like 1919 X 1079, or 1280 X 720... then the color change does not occur, even when exported! If I apply a resize to the same size, then the output is brighter again.

I am proof checking in Quicktime 7 of course, with "FCP compatibility" enabled and disabled.

I know this is a hot topic and there are many unsolved aberrations like this around this topic, but maybe there is something I don't get ?

Thanks 🙂