Styles and Techniques
High Dynamic Range (HDR)
Chances are, if you take a peek at the camera on your smartphone, you’ll notice a setting marked “HDR.” If you happen to use it, you’ll be treated to an image of vibrant, high-saturation colors and strong contrasts that almost mimics a painting. The truth is, this isn’t an HDR image at all (although they are fun to look at.) HDR is an acronym for High Dynamic Range. The method combines specialized multi-exposure shooting techniques with digital post-processing to produce contrast ratios that are generally un-achievable with a single exposure. It all sounds rather complicated doesn't it? The idea is actually fairly simple: If your camera can't get it all in one shot, shoot several and blend them together.
So what is dynamic range anyway? In real-world scenes, it's defined as the ratio between the lightest and darkest regions and can exceed 50,000:1. Unfortunately, digital camera sensors aren’t capable of capturing these ranges. In fact, traditional media has historically been limited to around a 300:1 ratio...that's a big gap. Ever shoot a picture inside your house on a sunny day? One of two things happens: (1) The interior is exposed and the exterior as seen through the window is blown out to white or; (2) the exterior is exposed perfectly but the interior is so dark you can barely make out any features. It’s not your fault. Cameras just aren’t capable of capturing such a broad range of light brightness…even with the groovy filter your iPhone applies.
To a large degree, this problem can be solved using High Dynamic Range shooting and processing techniques. With HDR photography, several exposures of the same image (1-4 underexposed images to catch the highlights that would otherwise be blown out, 1 properly exposed, and 1-4 overexposed to pick up the shadowed areas) are taken with a fixed camera (on a tripod) then digitally tone-mapped or blended together resulting in a much higher dynamic range. I find this method invaluable in a number of applications from architecture to (as seen below) scenes where the bright sun would make a single exposure nearly impossible.