Take a look at this screencap from this year's WWDC session 501 "Advances in iOS photography".

Screencap of session 501 "Advances in iOS photography" of 2016's WWDC

As an app developer, you can tell the camera subsystem to either use the 'video' pixel format or the 'full' pixel format.

I don't get why someone would want to choose the 'video' formats. If you're shooting a movie, chances are that you'll do post-processing anyway, so why not just take the full color range every time and post-process away the pixels you don't need?

I apologize if this question comes across as ignorant, but in an age where storage is cheap and lossless media (like music and photos) is ubiquitous, I don't understand why this is necessary.

  • 1
    Your assumption of post processing is very broad. If you're shooting a movie you may well spend more time editing than than shooting. But most videos and most video views aren't movies, they're short clips often shot in one take, with little preparation or post processing. They are also quite likely to be shot by someone who's never even heard of colour space, hence the choice being one for the dev.
    – Chris H
    Jun 15 '16 at 16:19
  • 1
    It's not nice to publicly share information that's covered by an NDA.
    – Caleb
    Jun 15 '16 at 17:37
  • We who shoot video (news/promotion) professionally spend much time in "pre-processing" our set-up menus according to strict test values established as "best practices" for our client. We use calibration standards and test charts for broadcast conformance standards. The same is true for theatrical production with the difference that the conditions are more controlled on a sound-stage or "set."
    – Stan
    Jun 15 '16 at 18:13
  • 1
    seems to me this question would be better suited to video.se
    – ths
    Jun 16 '16 at 13:20

The IRE (Institute of Radio Engineers) has determined the luminance range and gamma for Video to render properly. This is called the 10 point IRE scale and has pre-set values for shadows (16) to highlights (235).

Different points represent different luminance levels on the IRE scale. Below 16 is a "crushed black" or 0. No detail shows below this level. The 10% (1) level will hold detail. Detail in the highlight holds to 90%. Specular highlights appear above 90% but will begin to flare (saturate) above 10. 5 on the scale is a 50% mid grey.

I use these values for all my scans as suggested by Wayne Fulton in his FANTASTIC book "A Few Scanning Tips." Get that book if you use a scanner. BTW, I see that Fulton hangs around the SE.

  • 2
    is that the @WayneF batsignal I see? =)
    – scottbb
    Jun 15 '16 at 17:17

My understanding is that by setting up a system that reports clipping limits or over/underexposure at 13 and 235 instead of the actual hard limits of 0 and 255 sort of gives a little "cushion" for exposure adjustment later. I think you're right that it wouldn't be necessary if working in raw or even at higher bitrates but at 8-bits you don't have much wiggle room.

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