Whitewater Rafting -- Bulldog Bend

This weekend saw the annual whitewater rafting festival in Blount and Cullman Counties in north-central Alabama. For the most part, it was a tough weekend for the kayakers, with intermittent hard rain on Saturday and chilly weather on Sunday.

Here's a shot of an intrepid whitewater kayaker:

(Click on the image for a full-screen view of the photo.)

This shot was taken with a Nikon D700 camera and a Nikkor 80-400mm lens. The ISO was 400. Amazingly enough, I shot the entire event hand-held (no tripod or monopod), owing primarily to the difficulty in getting to down a steep, damp hillside to my vantage point while carrying anything more than the absolute minimum amount of gear.

The photo was taken at 400mm. Notice the compression -- how the foreground and background are brought close together. Compression is a side-effect of using telephoto lenses, and this is often a reason to make the selection to use a tele- lens rather than a shorter lens and a closer approach. The compression (and the associated loss of focus in the background) can be used to add emphasis to the subject, and to separate the subject from the background.

Colors were tricky. It was a heavy overcast, and Lord knows what "auto" WB would have given me. I used an Expo Disk to calibrate the White Balance, and it looks pretty accurate. Technically, the hardest aspect of delivering this shot had to do with getting consistently sharp focus on my shots. Here's how it was done:

Use AF-C, the Continuous Autofocus setting. This employs predictive autofocus, where the camera detects and follows motion, using the speed and direction of the subject to predict its position at the moment of exposure. Then, I used the 51-point 3-D tracking setting. This alloed me to select an active AF point, locate my subject and focus on it, then allow the system to continuously track the subject as it moved through the frame. Then, finally, I had to get a shutter speed sufficient to stop the subject's motion as the kayak bounced and glided through the course. I found it took about 1/250 second to stop that motion and generate a sharp shot. To get that, I found that I needed to use and ISO of 400 to get 1/250 second or higher at f/5.6.

All in all a fun day at the river, and lots of good shots to remember the occasion.