It’s hard to browse Flickr much now without running into a lot of these eerily-lit, surreal, colorful photos. These photos tagged with “HDR” are quite common in Flickr’s daily “interestingness“, and the HDR group pool is seeing a lot of activity. Here are a couple shots I took trying out this new technique:
So what the heck is HDR? It stands for High Dynamic Range, and the Wikipedia entry on HDR imaging does a good job of explaining it. Now, the above images are not actually HDR images (as Andy corrected me early-on), they’re tone-mapped images generated from an HDR image. Seems like semantics, but it’s sort of an important distinction that’s been completely lost during this trend.
Using software such as Photoshop CS2 or Photomatix you load multiple exposures of a scene, including full exposure data (you’ll need to shoot in RAW), and the software combines them into a single HDR image. The image contains the varying exposure possibilities for highlights and shadows, using the starting images you gave it. You can think of it as giving you control over the actual light in different areas of the scene. The tone-mapping process is essentially a way of taking all that HDR information and generating an image that shows all the best-exposed parts. It brings out details in shadows, under-exposes bright highlights, etc.
So what’s the point of all of this? Well, the HDR techniques and algorithms have a lot of applications in computer graphics, effects and video games, where natural light is one of the toughest things to simulate. In photography though, this tone-mapping is just a processing step, not unlike a Photoshop filter, which makes for a pretty image. Like shooting in infrared, or macro, or lomo, it’s another tool (some would argue a gimmick) which creates a unique photographic look.
If you’re looking to play around with it, the Flickr HDR group has a lot of tips and links to resources. Looking for interesting things to shoot? Scenes with high light/dark contrast work well since you’ll be under/over exposing your shot to pick up the details in both extremes. Skies and clouds end up looking pretty neat, and so do reflections.