HDR video - Isn't that 90fps from the image sensor?

[TechLord]

The Sony Xperia Z introduced HDR (high dynmic range) video to mobile phones in early 2013.
HDR combines an AEB (auto exposure bracketing) of 3 images usually onto one frame.

Does the image sensor (IMX135 Exmor RS) maybe process HDR itself? The Xperia Z never has sufficient processing performance for 1080p at 90fps if S4 does not even reach 1080p at 60fps.

[sneaker]

...

[Cornucopia]

That is not how the camera works.

Remember, this camera like most modern cams can do many megapixels (13MP here). In photo mode.
In video mode, it is not possible to get 13MP due to speed constraints. Like others, it commonly shoots 1080p, which equates to 2MP. Lots of extra pixels not used for video, or used & combined/averaged together.

So with HDR photo, it does multiple bracketed photos of progressive exposures (usually chg shutter speed to avoid shifts in DoF). It takes the pix, then the cam app uses the CPU to combine them into sort of HDR (though usually just optimized Tone-Mapped SDR). This can be done because of still photo so little worries about motion.

With HDR video, however, in this version at least, the sensor makes use of some of those extra (wasted) pixels, and much like binning & interlacing, it switches between alternate high & low sensitivity lines. They aren't necessarily normally higher or lower sens., but odd lines could be std 1/60th elec sec shutter speed (common 180degree, 1/2 dwelltime), with even lines at 1/120th sec (90deg, 1/4dwelltime), to give lower sens.
Then, much like deinterlacer, lines are combined (and then tone-mapped). Maybe in realtime, maybe with delay. Yes, it interpolates, like when debeyering.

Note that rarely is a true HDR-format photo saved (or for that matter, the contributing brackets). Even rarer is a true HDR-format video saved (e.g. *.exr, *.cin). Maybe never, in current consumerspace.

Under no circumstance does the cam do over 60fps (rarely over 30).

Scott