I recently spent four days in Havasu Canyon shooting the various waterfalls. Due to the spring runoff, the water was fairly high and moving pretty rapidly. On the third day, I was standing knee-deep in the water shooting Navajo Falls. After my last shot, I turned the camera off, folded the tripod legs, and headed towards the shore. Unfortunately, my foot slipped on some silt and down I went...5D, 17-40L, and tripod. The camera and lens were submerged only for a brief instant. After getting to shore, I detached the 17-40L and expected to see a camera body full of water. Luckily, not a drop was inside thanks to the gasket on the lens. The Kaesemann CPL also protected the front of lens from leakage. After getting back to the campsite and praying along the way, I powered up the camera and all was well. This is one of those "intangible" characteristics of an L-series lens. Yeah, they're a bit expensive compared to other lenses, but in this case it saved my 5D from complete ruin.
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