HDR Photography (High Dynamic Range) is a set of techniques that allow a greater dynamic range of luminances between the lightest and darkest areas of an image than standard digital imaging techniques or photographic methods, according to the Wikipedia entry. Typically you would snap a number of photos for the same subject, altering the exposure in each: under expose to capture detail in areas that would otherwise be too bright (the sky), over expose to pull out detail in darker areas, and one in-between. Then, using special software (Photoshop has some HDR abilities built in and there are HDR apps) to combine the photos so as to blend the best elements of each. The resulting HDR Images are some times surreal and other times you might not notice other than to wonder how the photo managed to be so nicely exposed.

In their iOS 4.1 update Apple added HDR as an option to the iPhone's (and upcoming iPod Touch 4?) camera program. When you snap a photo it quickly takes two or three pictures and performs a quick HDR composition. You are left with the normal image and an HDR version (there's a setting to turn off HDR and another to not save the original). Why two? Well, you'll quickly discover that not all images are conducive to HDR. If you are capturing a fast moving subject in low light (i.e. 3yr old on a hike) a normal photo might have a slight bit of blur. On the other hand with an HDR image, since each of the images are taken micro-seconds apart, the resulting photo may have multiple or misplaced fragments of the subject, as shown in this example.

Last night Faith and I were out on a date. After our meal we went for a walk around Lebanon. The photos are of a house for sale right on the green. Since it was around seven in the evening and the light was starting to go I figured it would be a good test of HDR on the iPhone. As for the house, let's just say it's a fixer-up special. Built in 1813 it has 8 bedrooms, 4 or 5 bathrooms, attached apartment/office and a decent sized yard. On the other hand there's not an unbroken window on the garage and it may have been a quarter century since any of this has seen a decent paint job. Great location, lots of potential, you can pick it up for only $795k!

Each of the photos shows the original on the left and the HDR version on the right. All in all the HDR versions came out better. On the final photo, taken a half hour or more later, the Sun was going down and while the HDR pulled out some details in the yard, I think the sky lost a little something. The only adjustment I made to these photos was resizing them in Photoshop and saving as JPG.