While in the field during my recent photo tour to Lake Clark National Park in Alaska to photograph brown bears I usually had my Canon Eos 1D MkIV attached to either my 300mm F2.8L IS or my 500mm F4 IS on a Gitzo CF tripod fixed with a Mongoose 3.6 gimbal head. Over my shoulder I would have a Canon 7D attached to the 70-200mm F4 IS using the excellent Black Rapid Strap system. This strap system allows me to quickly react to action when it happens.
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I was photographing a bear walking the opposite bank of the creek with my 500mm on the tripod when suddenly the bear charged into the water to attempt to catch a silver salmon.
I try to keep my exposure settings on the 7D and 70-2oomm correct for the expected shooting conditions. As soon as the bear rushed into the creek I was quickly able to grab the camera and photograph the intense action.
By keeping my ISO at 320 I knew that I would have adequate shutter speed to stop the action when it happened.
When the bear stood up to look for the salmon it had just missed I quickly flipped the camera to the vertical format for a stronger composition.