Tuesday, March 9, 2010

HDR (High Dynamic Range) is probably a misnomer and should be called CDR

As you can see here if you enlarge it I have used the trick of combining three exposures with +/- 2 f stops difference using a technique called tone mapping found in photoshop and Photomatix (shown here).  This is a very useful technique. However, lots of people are referring to this technique as HDR, or high dynamic range photography. I think this is probably wrong and should be referred to as Compressed Dynamic Range or CDR imaging, when presented on limited dynamic range screens, papers, printings etc.

The reason I am so sure about this is from my experience with music recording, some of it linked here in 640 plus posts about microphones. (in case you are remotely interested). In that field, the recording device is capable of recording a dynamic range far exceeding the playback equipment.  Audio clipping - the same concept as white clipping - creates a very harsh and unpleasant sound in the digital environment.  That's where gain leveling and finally the dark art of music mastering come in - so the music will fit in the "channel".  Same as the paper, screen or printed page, the channel is limited, sometimes severely, such as an MP3, or Sirius downlink.

Compressed Dynamic Range

Anyway, CDR is what is shown, above. Just an open garage on a sunny day. CDR can look pleasant and reasonably natural, eliminating the clipped highs (except on the left car) and the all-black detail-less shadows. I think CDR is going to be a standard feature in fast, burst shooting point and shoot cameras very soon, but they will still call it HDR.

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