High dynamic range video is without question going to look best in a dim viewing environment. However, given that content on mobile devices is viewed under a wide variety of lighting conditions, what are the best monitoring & delivery practices when editing Dolby Vision Profile 8.4 for social media?
Apple’s developer document Ambient Viewing Environment metadata with Dolby Vision™ Profile 8.4 playback notes that typical mobile device viewing conditions are 20X brighter than the reference viewing environment recommended for professional colorists:
“Starting with iPhone 12, apps can capture, play back, edit and export HDR Video with Dolby Vision. The normal office or home lighting when using an iPhone indoors is around 314 lux (a measurement of light level intensity). This is significantly different than most of the theatrical movie content graded by professional colorists, which is typically done in a dark room with the ambient condition at around 16 lux. In order to provide an optimal viewing experience, it’s useful to differentiate between the two types of content for wider viewing conditions. This is especially beneficial when playing back HDR contents on mobile devices where the ambient lighting condition can change dramatically.”
Not only can viewing conditions fluctuate wildly when consuming content on handheld devices, but the peak luminance of displays can vary from 600 cd/m² to 4,500 cd/m². Apple metadata assists in preserving the original intent:
“Ambient viewing environment [metadata] assists the receiving system in adapting the received video content for local display in viewing environments that may be similar or may substantially differ from those assumed or intended when mastering the video content.”
Dolby Vision Profile 8.4
“The ambient viewing environment atom (‘amve’) shall be present. Apple APIs will by default preserve the ambient viewing environment metadata when exporting HDR Video in Dolby Vision Profile 8.4.”
iPhone Auto Brightness Feature
The hidden auto brightness feature on iPhones adjusts the screen brightness for current light conditions using the built-in ambient light sensor.
Discover Reference Mode
This video explains Apple’s reference modes. Always use reference mode HDR Video (P3-ST2084) for grading.
HDR Monitoring
“For accurate HDR preview in most workflows it is recommended that external 3rd party hardware be used. AJA, Blackmagic Design and other manufactures have developed a range of commonly used devices that support connecting various monitors to a Final Cut Pro workstation. When using a 3rd-party I/O device, this bypasses the OS color settings and allows direct output from your editing software.” Alternatively, an Apple Pro Display XDR may be connected directly to a Mac, or you can use the built-in XDR display on recent MacBook Pros. No I/O device is required. Whichever monitoring setup is decided upon, 1,000-nit peak luminance is the minimum requirement for HDR editing.
Naturally, video can also be shared directly from mobile devices to social media platforms. Dolby Vision capture is the default setting on the iPhone 12 and later and is captured whenever HDR is enabled in the Camera app settings.
Average Picture Level: Let’s Talk
(1) When the mastering environment matches the end-user viewing environment, PQ and HLG should both have comparable image quality. It’s when the end-user viewing environment of PQ does not match the mastering environment that issues arise. That’s why Dolby Vision IQ (Level 11), which uses the TV’s ambient light sensor data to optimize playback, was developed.
(2) Whether watching content on Netflix, Apple TV+, YouTube or Vimeo, or mindlessly scrolling through Instagram Reels, it should not be necessary to leap for the brightness control whenever content mastered in HDR appears – if the picture is too bright, it is of poor quality, plain & simple. Speaking of quality, viewer expectations for HDR are not infrequently higher than for SDR content, and banding, compression artifacts, excessive sharpening, clipped highlights, motion artifacts, over-saturated colors and obtrusive noise in the shadows are all unacceptable – just as they have always been in SDR, only more so.
(3) Peak brightness of the deliverable should never exceed that of the mastering display. Furthermore, the brightness of uploads to video sharing platforms should be similar to that of the original footage. If not, the color management workflow needs to be examined. We’ve uploaded videos edited in DaVinci Resolve to YouTube, Vimeo and Moj and they are consistent across all platforms. Dolby Vision clips recorded on an iPhone and exported directly to Instagram Reels from the camera roll look pretty much identical. For content destined for television, bear in mind that the power budget of OLED TVs is considerably lower than that of many mobile devices, with full screen brightness often capped at ~150 nits or so. Full screen brightness greater than 25% of the display’s peak brightness is uncomfortable to look at anyhow.
(4) Preview your work on as many different types of devices as reasonably practicable.
Photo credit: Apple
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