Experimenting with HDR Photography

November 5, 2007 | Tags for this entry: hdr, Photography

Earlier this year I saved up and grabbed a Canon 20D. It was something I had waited a long while to get my hands on so that I could finally replace my Rebel film camera. Finally, after I wrapped a few freelance web projects, I got it!

Then, I put it on a shelf in my closet next to my film camera.It’s sad, I know. But the Web is a busy place, and I have been working on all this CSS, Ruby and Ajax stuff. However, in my link hopping a few months ago, I came across a tutorial of HDR photography. It seemed interesting, but quickly got too complicated for me to take a real interest since I was only casually browsing links on the ‘Net. Well, this evening I came across a few more links featuring HDR or High Dynamic Range techniques and tools that are used to achieve the effect.

What made me stop long enough to really read what was going on was the striking images that I was seeing produced with tools that are common to most graphic and web designers already. After a few minutes reading the previously-linked HDR tutorial at Vanilla Days, I grabbed my 20D and went to take some bracketed photos at 9:30 PM on a Sunday night! I took several sets, but here is the image I used to get started with HDR, (which is probably going to my new reason to keep an SLR on my hip 24/7).

Original Image, 2-second exposure, before any RAW white balance adjustments:

Basically, the technique involves bracketing your images with a difference of -2 or +2 stops. Your settings can be different and you don’t have to limit your composites to just three photos. Another option is to shoot a single RAW image and create your under- and over-exposed images that image. RAW offers you much greater image data than you’ll ever see in standard formats like JPEG and TIFF. (Don’t get the benefits of RAW mixed up with benefits of HDR. You could shoot regular images and then move on to HDR techniques, but all that does is limit your control in post-processing and kills some of your possibilities.)

HDR Experiment 1 – November 4, 2007

These images were taken using a 2 second shutter speed with a tripod and timer in RAW. Since I shot these in RAW, I was able to manipulate the white balance that I wanted applied to the images. I tested several and settled on ‘Tungsten’, since this pulls the orange out of images.

The three original photos: Tungsten-balanced, original -2 +2, respectively:

I used Photomatix to create my composite because I was less than pleased with Photoshop’s ‘Merge to HDR’ results (Found under File > Automate). Since I am only using the Trial of Photomatix, I saved the Radiance RGBE (.hdr) file that can be opened in most of the latest graphics programs. I did all of my color adjustments in Photoshop, since the ‘tone mapping’ option watermarks the images in the trial of Photomatix. No big deal there. Here is the result of my first experiment with High Dynamic Range photos:

Converted to 8bit with exposure of +13.13, gamma 1.00. I also pushed the saturation up to about +24.

As proof that there is definite value in this technique, I decided to try to replicate the results by simply taking the original RAW image and pulling the levels up and attempting to match the HDR version. Even if the color could be matched, it wouldn’t be as crisp. The reason is because the biggest benefit of HDR is being able to display greater detail in the highlights and shadows of the image.