August 23, 2012
Grizzly Bears and a Hoary Marmot in Glacier National Park, Montana, and Long Lens Shooting

The Grizzly Bear sow and yearling cub walked along the shore of Lake Sherburne yesterday morning in Glacier National Park. The cub is doing a great job following the example of its mother: in step and looking the same way. In the afternoon, I hiked up the Hidden Lake trail from Logan Pass. I photographed Columbian Ground Squirrels and Hoary Marmots in the wildflowers and Mountain Goat nannies and kids. It was great to photograph something other than bears from the road. I only took my small tripod with ball head and 500 up with me, and I couldn't believe how clunky the ball head was with the 500 after using a Wimberley Head for a few months. My knee was quite happy on the 1.5-mile (2.4 km) hike up to the top, but it wasn't happy on the way back. :(

Long Lens Shooting

I've started to change the way I shoot with my 500 f4. I used to shoot almost everything at f8, with and without the 1.4x, in order to get some depth of field. After talking with photographers in Yellowstone back in May, I consulted an app (simpleDOF for iPhone) to see what the depth of field really was for a long lens and a subject 100 yds (91 m) away, the usual distance for the bears. For 700mm (500 & 1.4x), f8, and a subject 100 yds (91 m) away, the depth of field is about 19 ft (5.8 m). This is for a circle of confusion of 0.00085 in (0.022 mm), so your mileage may vary. That's a lot of depth of field. Even reducing the f-stop to f5.6, the depth of field is still 13.4 ft (4.1 m). By comparison, for 700mm, f8, and a subject 20 yds (18 m) away, the depth of field is only 0.74 ft (8.9 in or 23 cm).

So, with that information, I've been shooting wide open more for subjects far away. That helps with the shutter speed and I can keep the ISO lower. For the image of the Grizzly sow and cub above, even though I was shooting with the straight 500 f4, I selected f8 to (hopefully) get enough depth of field to get the sow's eye and the cub's eye in focus, and I got it. (The depth of field for a 500mm lens, f8, at 50 yds or 46 m is 9.4 ft or 2.86 m.) For the image of the Hoary Marmot above, I closed down half a stop when using the 500 and 1.4x to get a shallow depth of field, and I really like the way the nearby flowers are soft which really makes the marmot pop.