![]() macOS 10.14.6 (Mojave) QuicktimeX Player Now we can move to final comparative tests and investigations to understand the core of the gamma/brightness shifts problem. Some monitor calibration software even warns you about possible compatibility problems and suggests to choose simpler but more compatible profile type. If you decide to calibrate your monitor manually and choose unusual profile type or some custom gamma curve, or use too complicated XYZ LUT based ICC profile type, you may expect problems with strange gamma shifts between different apps. Original bundled Monitor ICC profiles usually always designed within safe guidelines (Gamma 2.2 or sometimes sRGB and single curve+matrix profile type), so usually they don't cause any problems. Different ICC profile types provides different calibration complexity and accuracy, but same time may cause compatibility problems in some apps when it comes to color space and gamma transform from video source to monitor profile. Monitor ICC profiles may have a lot of different types (XYZ LUT based, LAB based, Curve+Matrix based, Gamma+Matrix based). As i remember, Windows OS is not system wide color managed for video, so it always relies to video players and apps own internal color management. Older versions of VLC and most other video players, as well as Firefox browser can't read any of video metadata tags and so always output video "as is" without any additional color or gamma transforms. VLC output is usually 100% match to DaVinci Resolve viewer output if “Use Mac Display Color Profiles for Viewers” turned OFF. VLC don't read Rec.709 gamma metadata from video file and don't transforms it in any way. It only transforms color space described in video metadata tags to monitor profile. It reads only "Color primaries" and "Matrix coefficients" metadata tags. ![]() VLC Player v3 use it's own internal color management processing. It reads Timeline ColorSpace and Gamma settings (or "Output Color Space" project settings if you use YRGB Color Managed workflow) and transforms them to monitor profile. When you check “Use Mac Display Color Profiles for Viewers” in DaVinci Resolve Preferences->System->General, it attempts emulate that specific macOS color management. ![]() This gamma color management method is rather exotic and unusual among other apps and video players, so as a result video output on mac always have that slightly brighter gamma look. All macOS system apps (QuicktimeX player, Preview, QuickLook, Safari browser) always read "Color primaries", "Matrix coefficients" and "Transfer characteristics" tags from video file and transforms color space and gamma described in video metadata tags to monitor profile. If you use YRGB Color Managed workflow, DaVinci Resolve adds metadata tags according to selected Output Color Space in project settings. The amount of supported metadata tags in video files is limited to few common color spaces and gammas, so if you set Timeline to some camera specific Log gamma and wide gamut Color Space, DaVinci Resolve will not add any metadata tags to rendered video file. Things may be different in older versions of DaVinci Resolve. If you use DaVinci Resolve 16.1 and set project to YRGB (non color managed) workflow, it adds metadata tags to rendered video file according to timeline settings (Rec709, Rec2020, PCI-P3, Linear, g2.2, g2.4, g2.6 and so on.). DaVinci Resolve Color Space Transform Node or LUT attached to clip or to timeline does not add or affect metadata tags. Some apps can read all those tags, some can read some of those tags, and some apps just ignore all those tags. Modern color management for video is not standardized enough between different apps and operating systems. To see those metadata tags you need some media file inspector app (Invisor, VideoSpec, VideoScan, MediaInfo) You can find full list of supported tags here "Transfer characteristics" describes gamma setting. "Color primaries" and "Matrix coefficients" describes color space settings. These metadata tags describes color space and gamma for apps that support color managed video output. There are 3 main metadata tags located inside video file: ![]() It is also NOT related to various types of HDR metadata tags.) It is NOT related to incorrect setup of Full/Video levels in Project/Render settings which may produce darker/lighter image. (This investigation is NOT related to legacy outdated Mac OSX versions gamma 1.8 vs Windows gamma 2.2 shift problems in quicktime. This problem is rather complicated and consists of multiple factors. This is my attempt to understand and explain gamma/brightness and color shifts problems between different video formats and players. ![]()
0 Comments
Leave a Reply. |