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Thread: Canon 17-40L weather sealing warning

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    Canon 17-40L weather sealing warning

    Like everyone else I did the testing and determined that UV filters degrade image quality, and in the case of Canons AF accuracy and reliability as well, and only use UV filters when things are flying at my front element. However, it appears that Canon lenses need the filter for sealing.

    This past week we were shooting video with a 7D and 17-40L, including two close car to car shots on a dirt road - one with the camera attached to the front of the video car with a suction cup, the other with the photographer holding the camera and shooting out the back of the lead car. After those two shots, totaling at most three minutes, with vehicle speeds at 25 mph, the INSIDE lens elements were completely caked with dust. Not a little dust, totally covered. I would say that the lens was exposed to about as much dust as getting caught on the prairie on a windy day.

    This is the second time the lens is going back to Canon for disassembly and cleaning after shooting in a dusty environment. However, to put the level of dust in perspective, we shot with three cameras, changing lenses on all of them every few minutes and never got a spec of sensor dust on any camera.

    All I can surmise is that the lens needs a filter on the front to seal it as it looks to have some space between the plastic on the front and the outside of the lens barrel. However, when we noticed the dust was after the shot with the photographer hanging out the back of the lead vehicle. In that shot, the dust was moving straight up from the road, hitting the lens perpendicular to the barrel.

    As much as Canon touts their weather sealing and quality of their L lens construction, this was a bit of a surprise. I don't have any specific recommendations since I don't know exactly how the dust entered the lens, but consider yourselves warned.

    On a side note, this was my first exposure to the 7D. I never shot with it, but was extremely impressed by it.

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    Re: Canon 17-40L weather sealing warning

    I know the 17-40 needs a front filter to provide weather sealing. The description of the 17-40, in the Canon web site, concludes with: "Finally, it offers weather-resistant construction similar to other high-end L-series lenses."

    I think if you look at your manual, it will mention that the lens is not sealed without a filter.

    Like you, I don't use filters. But after reading your experience, I may keep one in the bag when the dust kicks up.

    Jim

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    Re: Canon 17-40L weather sealing warning

    Bill,
    Sorry to hear about that experience with the 17-40. I do think that Canon does say in its specs about that lens (plus a few others in the "L") line that they do need a front filter for best sealing. Many of the longer lenses either have an optical glass already in place as a protector, or are sealed differently and do not really require any other front filter to be in place. I have found the even using something like a lens hood, which has no direct sealing to anything does help cut down on incoming dust. (I shoot at a lot of horse shows, and when the ground is dry, the super fine dust raised can get into places you would never imagine. Shooting the 24-70 f2.8L in those situations, always with a lens hood, I have never had any dust nor moisture problems, even in heavy rain storms. Also have never had any issues with the 70-200 f2.8L under same shooting conditions. My 400 f2.8L IS has a separate optical glass sealed over the front element, and that makes it pretty environment proof....especially in heavy rain situations. Have not had a single dust or moisture problem yet.....knock on wood. All that being said, I do recall folks having problems with the 17-40 ever since it was released, and I do think there is something in the lens manual that says it requires a filter to complete the sealing.

    LJ

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    Re: Canon 17-40L weather sealing warning

    Thanks LJ, good to know. I will pass that on. I shot in extreme weather for years without problem with my Canon gear and my total equipment failure in 10 years was one battery.

    Looking back at production stills, the only time the filter was off was the shot where the camera was hand held in the car. On the driving shots with it attached to the car, and the Morocco trip where it got dusty the first time, there was a filter in place.

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