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Thread: Dust found in lens, Normal or Abnormal?

  1. #41
    Member jsprtan's Avatar
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    Default Re: Dust found in lens, Normal or Abnormal?

    Quote Originally Posted by Rashkae View Post
    Thank you for proving my point. You're the one who goes on and on about the L lenses being airtight, yet you just contradicted yourself.

    I suggest you read up on what "weather-resistant" means. Simple water splashes are fine so long as there is no additional barometric pressure on the seals.
    Did I? Please read the post again.

    Well, the Key word here of is barometric pressure.

    Here I think simplest way for the lens to seal is with a simple old ring assembly with a certain amount of pressure to keep it tight. So at normal atmospheric pressure it will not fail thus creating a tight seal that prevents air or liquid from flowing through.

    However at higher pressure, the reaction to the assembly of the system will be entirely different. As the pressure increase under water (1 bar per 10m), the difference in pressure internally and externally will create a certain amount of deformation on the housing hence reducing the pressure that is applied on the seal and causing it to leak.... This is where the difference is between submerging and splashing. That is why all underwater cast have to rated to a certain pressure rating as it is not logical to over design.

    I am not the one designing L -Lens so sure I have no idea what they have done..
    Last edited by jsprtan; 23rd July 2010 at 02:21 PM.

  2. #42

    Default Re: Dust found in lens, Normal or Abnormal?

    Quote Originally Posted by jsprtan View Post
    Did I? Please read the post again.

    Well, the Key word here of is barometric pressure.

    Here I think simplest way for the lens to seal is with a simple old ring assembly with a certain amount of pressure to keep it tight. So at normal atmospheric pressure it will not fail thus creating a tight seal that prevents air or liquid from flowing through.

    However at higher pressure, the reaction to the assembly of the system will be entirely different. As the pressure increase under water (1 bar per 10m), the difference in pressure internally and externally will create a certain amount of deformation on the housing hence reducing the pressure that is applied on the seal and causing it to leak.... This is where the difference is between submerging and splashing. That is why all underwater cast have to rated to a certain pressure rating as it is not logical to over design.

    I am not the one designing L -Lens so sure I have no idea what they have done..
    http://gdlp01.c-wss.com/gds/7/090000....2L_USM_EN.pdf

    Maybe the manual will give more light...

    Look at Point 5 at on the right side.

  3. #43
    Member jsprtan's Avatar
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    Default Re: Dust found in lens, Normal or Abnormal?

    Quote Originally Posted by paesyl View Post
    http://gdlp01.c-wss.com/gds/7/090000....2L_USM_EN.pdf

    Maybe the manual will give more light...

    Look at Point 5 at on the right side.
    Hahaha.... it says dust and water proof... Here Canon is buying insurance from claim. As they would have propablilty used a rotating seal assembly and it is naturally with all things this will wear off over time.... Which is dependent on the usage. SO if it wears it will leak....

    BTW, AN O ring is just a fancy name for a rubber ring to seal things out....
    Last edited by jsprtan; 23rd July 2010 at 03:08 PM.

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