[midasuni]

A 32 bit float and only represent 2^32 numbers (maybe less), same as a 32 bit int.

What’s happening here is using a short (16 bit) rather than a byte (8 bit), although not quite to the same extent, for each channel. HDR allows you to represent 2^6/12/18 times as many colors as SDR.

[geocar]

HDR10 is 10-bits per component and there are plenty of 16-bit images that aren't HDR, for example: http://i.imgur.com/Wm2kSxd.png -- the main thing about using HDR is to increase the range of values, i.e. what the biggest and smallest values are, not merely how many distinct values you can represent.

[midasuni]

Well that’s just the colour space, you’ve also got the gamma curve to consider when you look at the perception of how something looks