HDRI, making tough shots easier since 1850!

Tone-mapped image from three exposures using Photomatix

HDRI (High Dynamic Range Imaging) is a relatively new trend in mainstream photography, but I bet there are many who don't know it actually began as early as the 1850's by Gustave Le Gray and his use of multiple negatives in the printing process.

It's the process of combining different exposures of the same scene into one image that shows the entire luminosity range of the exposures. And while it can't turn a bad composition into a good one, it can make a good picture really pop.

So what's so special about it, you say? Can't I just use a neutral density filter--which reduces scene contrast, and therefore increases the effective dynamic range--and get the same result?

Well yes, and no. Using an ND filter will allow your camera's sensor to capture a larger tonal range. But the inherent drawback in that is the increased amount of time that the shutter must be open to gather enough light. That lends itself to more sensor noise and motion blur, which may or may not be desired.

By not using a neutral density filter, shorter shutter speeds may be used, which will result in less motion blur. On the other hand, since multiple exposures are required, this may be a moot point since acquiring those exposures may take the same amount of time as a single shot with an ND. And what if you need to capture ten or more stops? That would require some pretty serious filtering.

HDRI was only introduced to the general public a little over ten years ago, but it's an increasingly popular trend these days. There are several programs specifically made for processing HDR images, like Photomatix or FDRTools. I encourage you to try it out for yourself and let me know how it goes. And if you've never used a neutral density filter, well, those are pretty good too, so I'm told. ;)

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