[fillest]

The thing about compression is wrong. "HDR photography" compresess for the eyes (let's simplify and leave the brain out), it has nothing to do with displays. If a part of a photo is too dark, the details will be clipped out for your eyes, no matter how much bits they will be encoded with - it will be just too dark.

In reality eyes can adjust the "exposure" on the fly because they recieve all the needed information always. But in a displayed digital image this information is already lost - eyes don't recieve all these bits, the display doesn't send them.

In the editor you can adjust the "exposure" for the RAW files too - they have the needed information - but! - it is not a static image, because you are adjusting it, you are sending continuously different information to the eyes.

[jillesvangurp]

Actually, your eyes have a better dynamic range than cameras or displays. More specifically, the process of going from a scene, to a photo sensor, to your monitor, and eventually to some paper is basically reducing dynamic range and either compressing or clipping to deal with the physical reality that each subsequent medium has less dynamic range.

Real life has an infinite (practically) dynamic range that is perceived by our eyes with about 20 stops of EV (exposure values or stops). A high-end sensor would capture maybe 12-14 of those. So, at that point you are already making creative choices (e.g. expose for shadows or highlights).

HDR in photography is the notion of combining multiple exposures to recover detail from a wider range of exposure values; which then get compressed down to the EVs of your monitor, which would be something of 8-10 stops typically (maybe more with these new fancy screens). And finally, printed materials have a dynamic range that is far less than that. 4-6 EVs.

High bit rates in raw files (12 or 14 bits are fairly common) means you have more data to work with when compressing values or otherwise manipulating the image data; which is a lossy process that involves rounding errors that can build up. When black and white can be apart by as many as 14 EVs, those extra bits are nice to have as well.

The point of high bitrate displays is more accurate color reproduction. Higher bit rates allow for more smoother gradients between colors. 8 bit color spaces were good enough for displays for a long time. But now that we have displays with higher contrast, deeper blacks, and brighter whites (i.e. a better dynamic range) the few extra bits of precision are useful. Especially on high end screens intended for graphics professionals, this is nice to have.

Of course this only makes sense if the input has a large bitrate as well. Apple is involved in HDR video formats with high bitrate that are getting common on cameras. Also recent beasts like the new Sony Alpa 1 produce 8K video with 10 bits. So that requires some beefy hardware to process, which Apple of course provides. Down-sampling 10 to 8 bits on a monitor is nice to be able to avoid while you are editing; even if your output is going to be lower quality after you finish editing.

[dreamcompiler]

You're describing perceptual clipping, which is orthogonal to dynamic range (DR) compression. There's no reason you can't do both, but HDR photography has traditionally been about capturing a wider range than the camera's sensor can handle and then mapping that data into a narrower range. That "narrower range" is determined by what the display technology is capable of and what common file formats assume. Nonlinear perceptual response curves and clipping can of course be factored into the mapping, but that mapping process is still DR compression.

None of the above has anything to do with data compression which JPEG does to decrease the number of bits needed to store a file; that's a different concept from DR compression.