Notice anything interesting about this group of photos? I took them in succession, but at different exposure values using the exposure compensation feature with my Canon Digital Rebel XTI. The first image is two "stops" underexposed, the second is one stop underexposed, the third image is what the camera's computer thought was an ideal exposure for this scene, and the fourth and fifth images were overexposed by one and two stops, respectively.
The bottom line is that before digital photography, you had to choose one exposure and stick with it. Especially when using slide film. Which image would you have chosen to best represent the scene? More detail in the sky, or more detail in the plants in the foreground?
The bottom line today is that with digital imaging, you don't have to make this choice anymore. There's a technology, and an art really, known as HDR imaging that solves this age old problem and really puts digital photography over the top.
How did I found out about HDR? Upon joining FLICKR last fall, I was noticing some incredibly interesting images that looked like they were taken in real life, but had the lighting and look of computer animation. Images like this one and this one.
After doing some research, I found out that these fantastical looking images were called HDR, or high dynamic range images. These images, are in fact, a compilation of differentially exposed digital camera photographs all compiled into one image, in order to fully express the range of dark and light tones in a scene. Dynamic range is simply the difference between the lightest light and the darkest dark in a scene. Today's digital cameras don't capture a very wide dynamic range (neither did slide film, print film's range was slightly wider).
Have you ever noticed that your camera can't capture a sunset very well? Even though you might see color in the foreground of the scene you are viewing, the camera isn't able to pick that up. Or if your camera sees the foreground, then the sunset is washed out and really bright? Let's look closer at the first and the last image.
High dynamic range imaging looks to eliminate that problem that I have so crudely illustrated above. The goal is to present an image that more accurately represents what the eye sees rather than the camera sensor. After putting together an HDR image, you go through a process called tone mapping, and voila, you've got a pretty darn cool looking image.
And producing a high dynamic range is quite easy. Making it look really good is something that I'm still trying to figure out. I have seen some incredibly realistic looking HDR landscape images that don't look fantastical or computer generated.
There are several free downloadable software packages out there to get you started on the HDR path. I've been using Photomatix. What else do you need? Well, a digital camera with some type of exposure compensation (most Canon cameras have this, even the bottom of the line models), and preferably a tripod, but this is optional. I didn't use a tripod to capture the above images, and the Photomatix software can align a series of images for you if you shoot with a steady hand. It even has a feature to remove "ghosting" from the images, usually things like moving people, which certainly was helpful for me in this beach scene of Sanibel Island.
So, you're probably thinking, "OK, I'm ready to see the final product". Well, for that, I might draw this out just a little bit longer! I'll post my final image tomorrow. But for now, try going outside and taking a few image series, download Photomatix, and give HDR a try!
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