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.


Maximg4040 said...

Your completely right about CDR! and also glad to see you gave it a go!

Bob Crowley said...

Ha! It was your blog that got me going on it with Photomatix!

Thanks for the link and I am about to pay them. I enjoyed using it much better than PS. Just much more fun. Your dramatic images gave me an idea for a shot of the old Polaroid factory, now all covered in graffiti. It involves several instant photos scanned in.

You can sometimes see "real" HDR on tv, when a bright scene fades to black, but it's brief. Also intrigued about how to make the gear to use CDR/HDR on moving subjects.

Maximg4040 said...


thats a time-lapse film shot completely in "hdr" I know its not filming moving subjects as it is just time-lapse but it is still interesting to look at

The shot of the Polaroid factory sounds great let me know how that goes!

Mustafa Umut Sarac said...

Do you know how Leitz lenses create these kind of images 60 years ago ? There was no computer or modern films but they are similar to these pictures. Same thing is for russian optics !
Industar and Jupiter is creating the dense colors and strong shadows and and highlights like computer 3D rendering .
I still have no idea how did they do it .
If you have knowledge , please share with us.
By the way , thank you about good words about my blog , your blog is better than mine.

Bob Crowley said...

There is a lot of interest in this. I notice that youtube has a lot of time lapse HDR of clouds and oceans. But I think I want a simultaneous, or virtually simultaneous 3 bracket system with speed enough for a fairly quick shot - maybe not a grab shot, but at least hand held.

Today was not the day for that shot. But I'd better get over to my assumed vantage point before the leaves come in. It's sure to attract the police.

Bob Crowley said...

Mustafa- this is the magic of what we called "the front end" in music production. The microphone plus the preamplifier, and the converters, made such a difference and that was carried through all the way to the end of the finished recording, even in digital.

Now we see this with analog photography - the front end is the lens and the film, and how we process it, later which we scan or somehow get onto the screen so we can share it worldwide, instantly.

The idea of "film" is not very different to me than a storage card. Yes the process is different and affords benefits and tradeoffs. But now we are thinking that film as the spatial storage medium it is has certain qualities that have still not been recognized.

Thank you for your kind comments - your blog is amazing for its directness, and I like those little habitats!