So, you’ve heard some folks talk about “high-dynamic range imagery” or HDR, and you think you sort of understand it, or not really?  Well then, I hope to de-mystify it for you in a series of blogs.

In my previous blog, I talked (or more like bitched) about why cameras suck; and one of my reasons was that they lacked sufficient dynamic range in capturing light.

“…, let’s talk about dynamic range.  This is the whole problem of the images above.  We’re only stuck with 0-255 per RGB channels.  This means that we need to describe the brightness of what we see — from dark shadows to sunlight — within the integer range of 0 to 255.  Even RAWs don’t cover it since the dynamic range needed to describe what we see could be 0-1,000,000.  Yes, cameras suck.  There are high-dynamic range imagery, and I will talk more about that soon.”

As shown above, there are series of photos that describe this problem.  In the beach shot 1, you see that the exposure was very long, so most pixels are washed out, but you can still see some contrast in the dark parts of the palm trees as well as the dark shadows on the sand ridges.

As the series of images get darker, e.g. beach shot 2 and beach shot 3, you can see the scenery much better, but the bright area around the sun is still too washed out.  By beach shot 6, we can see some outline of the sun better but everything else is now too dark.

Somewhere in this series of variously-exposed images lies the “right” answer for the composite image — this is the dynamic range problem.  Our eyes can see much better contrast than any of these camera shots (also because we can dynamically adapt better too, but that’s some other blog).  You can imagine manually photoshopping these images to get the solution image you want.  A more automated way is to create a single high-dynamic range image from this series of images, then tone map it.

Putting aside the technical lingo bullsh!t, I hope I’ve convinced you that there is a way to combine these images somehow to get the final image you want. (And I won’t bore you with the tech details either — if you must know, let me know pls.)

There are nice software products to do just this: Photoshop, Photomatix, and Enfuse.  There are more, but these are the ones I like.  (If you have your favorite, please comment and share!)

Beach shot "combined solution" using Photoshop

Beach shot "combined solution" using Photomatix

I’m not showing Enfuse just yet since it really isn’t HDR.  But I’m gonna stop right here for now, since the blog is getting too long.  I will talk more about Enfuse and more of HDRI-related issues in part 2 of this series.