View Single Post
Old 25th September 2018, 16:59   #52729  |  Link
nevcairiel
Registered Developer
 
Join Date: Mar 2010
Location: Hamburg/Germany
Posts: 10,344
Quote:
Originally Posted by huhn View Post
the banding part is a myths a proper dithered image will not show banding
Sure, you can prevent banding with dithering, but you do that at the expense of the noise floor.
All these transfer functions exist to move bitdepth around into areas where it matters for the format in question, because bitdepth is ultimately limited.

Gamma/SDR transfer functions are designed for a limited range of brightness, ie. the SDR brightness, so it spreads the bits around for that. If you try to push 1000 nits of brightness into a image transfer designed for ~120 nits or so, there will be a downside to that, because its not aware of the increased range of brightness.

PQ is designed to keep more bitdepth for the relevant parts (ie. 0-100 or so), and waste less bits on the 900 remaining nits, which are of less importance then the actual image detail.

Of course you can mask these differences with dithering, but ultimately a PQ curve is going to give you a better bitdepth distribution for HDR images, which have the majority of image data in a small subsection of the bitdepth range, and only highlights in 90% of the remaining space - as the transfer should reflect that.
__________________
LAV Filters - open source ffmpeg based media splitter and decoders

Last edited by nevcairiel; 25th September 2018 at 17:01.
nevcairiel is offline   Reply With Quote