Apple introduced many new features to its iPhone 12 lineup. Many people know about its 5G cellular capabilities, better camera (improved sensor and new ProRAW format), and faster processor (A14 Bionic chip with better performance and power efficiency). However, fewer people are aware that it also introduced a Dolby Vision HDR video recording option. This is kind of a big deal if you are a serious videographer, and it may also be a very useful feature for casual videographers like me. The purpose of this primer is to help you understand what high dynamic range (HDR) video is and why you might or might not want to enable it on your video recordings.
Let’s start by discussing what HDR video is. In short, there are limitations to the colors that computer screens can display as compared to what colors the human eye can actually perceive. Standard dynamic range (SDR) video is captured with 8-bit recordings which capture a very good representative sample of all the colors that human eyes can see. HDR video ups the game to 10-bit recordings which capture an even better representative sample of what humans can see (but still falls short of capturing everything humans can see). The result is truer pure red, pure green, and pure blue colors, as well as all color combinations of reds, greens, and blues.
Taking this a step farther, techies refer to these representative samples of colors as a “color gamut” or “color space” which you can liken to an artist’s palette. The more colors you can mix on a palette, the better you can paint the true colors of a scene. Color spaces are represented by CIE chromaticity diagrams. CIE is French for Commission internationale de l'éclairage which was established in 1913 and is also known as the International Commission on Illumination. In a CIE chromaticity diagram, the full range of colors is represented by a horseshoe-like shape, and triangular shapes represent color spaces of a variety of different SDR and HDR video formats as depicted here:
A given display can only reproduce the color combinations that reside inside the triangle that is formed by its primary (red, green, and blue) colors. As you can see, HDR video (e.g., Rec. 2020 color space) can reproduce a larger subset of colors than SDR video (e.g., Rec. 709 color space). The end result is higher luminance (brightness intensity) and more detail in both shadows and highlights.
From what I can tell, there are similarities and differences in HDR videography and HDR photography. From a technical perspective, HDR video boils down to a wider color space. HDR photos, on the other hand, are images that are the result of the blending of multiple different exposures of the same scene, all within a single color space. Also, HDR photos can be viewed on any display, while special HDR displays are needed to fully leverage the wider color space of HDR video. So the HDR look is achieved in very different ways between HDR photos and HDR videos. However, what HDR photos and videos share in common is that you can get better representation of tonal range. Note that one can go overboard with HDR photography, and that might be the topic of another blog.
Although HDR video is “better” than SDR video, there are potential tradeoffs. First, HDR video requires more storage space than SDR video, so this may impact how much video you can save on your iPhone as well as iCloud (if you use that service). Second, because there are lots more computations involved, recording HDR video requires more energy and can drain your battery more quickly. Finally, if you share and/or edit your HDR videos, you may need to be mindful of the color spaces you want to support. Most of the common sharing options automatically adjust for differences in color space and ensure compatibility. For example, when editing and sharing HDR videos in Photos, Clips, iMovie, and other applications, you will be prompted to specify the color space. Things are currently a little more complex for Final Cut Pro where you need to create a new Final Cut Pro library and set the color processing for the library to Wide Gamut HDR and then tweak some other settings. Color space conversions and tone mapping might be the topic of another blog post, but for now check out this Apple support page and this Apple white paper for more information.
All of this leads us to a single question: Should you enable HDR video recordings on your iPhone 12? I’d say yes if all of the following are true:
- You care about getting better color quality (it might not be noticeable to casual observers but might make a difference to those who have an eye for color “trueness”)
- The differences in storage space and battery life are not a concern (probably not a significant deterrent for most people)
- You are sharing videos by “conventional” means (i.e., via Apple software applications) which automatically make adjustments or prompt you to ensure color space compatibility
- If you edit videos for the purpose of publishing them to other platforms (e.g., YouTube), then you are willing to learn about supported color spaces and the conversions between them, in case issues arise
To enable or disable HDR video on your iPhone 12, go to Settings > Camera > Record Video and toggle the “HDR Video” option. If you’re interested in learning more about color spaces, a good starting point might be this series of lessons in Khan Academy.
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