Comment by oktoberpaard

What you are taking about is also called HDR, but has nothing to do with what the other person is talking about. The other person is talking about the still image equivalent of HDR video formats. When displayed on an HDR capable monitor, it will map the brightest parts of the image to the extended headroom of the monitor instead of tone mapping it to be displayed on a standard SDR monitor. So to be even more clear: it defines brightness levels beyond what is normally 100%.