That would be because HDR is not a word, it's an acronym. An initialism, to be more precise.mackguyver said:I had to do it - looks like there is no definition of HDR so all of you are right and all of you are wrong:
HDR = High Dynamic Range
From a technical standpoint, 16-bit and 8-bit images don't contain enough data space to truly qualify for the HDR moniker. They are what we call LDR or Low Dynamic Range files. A true HDR image is one stored in a file format that has an extremely large data space. Something like a 32-bit float TIFF, which contains a MASSIVE data space that can represent brightness values from something say as tiny/dark as 0.000001 to something as large/bright as say 100000000.
When we merge to HDR, we usually merge multiple source exposures that represent more total tonal range than is possible to record in a single 16-bit file, then save the merged result to a 32-bit Float TIFF. From there, we either downconvert with an algorithm (i.e. local adaptation) or manually tonemap the wide dynamic range of the HDR into the narrower dynamic range of a 16-bit or 8-bit image for publication online.