For those that don’t know what HDR is …. its an acronym for High Dynamic Range and it’s a method of blending multiple images together to create a single image composed of the detailed elements of all the images.

Why do it?
The main reason is to do with limitations of a camera sensor/film Vs the human eye.
If you were to look into shaded woodland with the sun overhead then the human eye can almost cope with the extreme bright and extreme dark that’s visible …. almost.

Ansel Adams created a zone system which segments the extreme Low and High tones.
The human eye (amazing thing that it is) can see a huge range of zones, most film can see about 4/5 of the range at a time and 35mm digital cameras about 3/4 (although they’re getting better every year). But the bigger the sensor chip, the bigger the range of tones captured.

11 stop zone chart from Imroy at wikipedia

Because the camera sensor is limited, when you take a picture of a subject which is an extreme zone you can "bracket" your exposure over multiple shots and pull all the data from each one to create the single image with the composite detail from the darks to the lights.

You can do the composite in-camera, but more often than not people use software which’ll do an HDR composite for you in a minute or two.
Most commonly Photoshop and Photomatix.

Good right? Not quite 😉

  • The good is that if you don’t have time or experience in editing then you can pull together an interesting image quickly and with little effort.
  • It also can create surreal images which are more like paintings than pictures, although some photographers tend to look down their nose at those

But there are downsides.

  • You have no control over the final result. Ok, you can adjust the intensity of the tonemapping, but it’s applied to the whole image
  • If you have any noise…. any at all in the image, then the HDR process will multiply it and it can look pretty bad (esp. in extreme tone mapping)
  • You have to take up to 9 exposures to get 1 final image which eats into storage space.
  • If you move the camera, even a fraction, between shots then chances are it won’t work.
  • It’s ok for 1 static subject, but a nightmare if you want to do a panorama, stop motion sequence etc…
  • If anything moves in your shots (trees, water, politicians, skateboarders…. :)) then they’ll repeat as ghosts – ruining the final image

So …. do I use it?
Yes and No. I rarely do HDR as I’ve developed a workflow that means I don’t need it, but that’s not to say I won’t do it if I’m in a pinch …..

The closest I get in reality when in extreme conditions is to take a 5 stop bracket (-2 to +2) and when I’m editing I’ll choose the best one of the 5 to edit rather than doing an HDR composite.

I’ll explain how to create a dynamic image with a single exposure in my next post. More to come…. 🙂

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