HDR is a technique which addresses the problem of a camera's limited dynamic range (refer back to this older post for an explanation of dynamic range). In an image with both very dark and very bright areas, the camera can't capture detail in both the dark and bright areas, it has to expose for one or the other.
To create an HDR image, you take multiple exposures of the same scene, each at a different exposure. Then, special HDR software combines the different exposures, pulling detail from each one. Finally, in a process called "tone mapping", the software compresses the dynamic range of the image so that it can be displayed on a screen (Not only do cameras have a limited dynamic range that they can capture, but screens have a limited range that they can display).
I'm still new to HDR, so I'm hesitant to explain in more detail until I understand it better myself. Here are some of my first experiments with the technique, though.
To take these three exposures, I used my camera's auto-bracketing feature to take exposures at -2, 0, and 2 stops. Since I'm just playing around, I made things simple and didn't use a tripod. Instead, I set the camera's drive to multi-shot, or whatever it's called. I framed the shot, then held the shutter release and it quickly fired off my three bracketed exposures before the camera moved too much.
There are two options for creating an HDR image. Photoshop includes an HDR tool, but the more popular program seems to be Photomatix. You can download a free, unlimited trial of Photomatix which places a watermark on your final image. This is perfect for playing around and learning the technique. If I decide later that some of the photos are worth having, I can plop down the $80 for the full version.
Here's the result from combining the above three exposures.
Pretty stunning for so little effort, eh?
The original images are all unedited, straight from the camera. And if you give Photomatix a try, I think you'll find that it's quite easy to use. You launch the program, press "Generate HDR Image", then select the exposures you want to combine. The initial image it shows looks pretty strange because it hasn't been tone mapped. The tone mapping screen gives you a handful of sliders and settings to play with. I think you'll find, though, that the settings aren't too overwhelming. You can reasonably just play around with them until you find what you like.
Stuck in Customs has a popular HDR tutorial at his website. There may be other better-written ones out there, though. I'll share what I find.
Here are some other HDR shots that I tried. This one was in the Alice Keck Park memorial gardens in downtown Santa Barbara (funny tidbit--Alice's last name was 'Park', so it's Alice Keck Park Park).
This is the Santa Barbara mission.
There was a small compositional trick I played in this Mission photo that I was proud of. The Mission actually has this big ugly asphalt parking lot in between it and the grass. By getting really low to the ground, I cut the parking lot out of the picture and added some foreground to the image (the grass).
The HDR technique seems to really exaggerate the dust on the lens in the photo of the mission. I need to look into that, I'm worried some of that dust may be on the camera sensor.
Anyway, I'm interested in learning and experimenting more with HDR, and I'm looking forward to sharing what I find!