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Thread: What could I do? Blemish on my EFS 18-75 mm kit lens that is 3 years old?

  1. #1

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    Arun

    What could I do? Blemish on my EFS 18-75 mm kit lens that is 3 years old?

    My EOS 40D kit lens: EFS 17-85 mm Lens bought with my camera body in 2008.
    I put a lens protecting neutral filter on the same day as I bought my equipment.

    This sunny noon I was just inspecting my lens & happened to discover through the front filter and deep to the front surface of my lens glass on the front surface of the real convex surface of the lens, I could see a very tiny web looking [like a dendrite pattern-shape of a neurone] disfigurement. I cannot reach to clean this.
    This is off centre of the axis of the lens. This I wondered if caused by cracked flacking of the lens coating?!!

    I am sure this may influence the light at larger aperture. However I have not noticed any interference on the photos[May be I do not know how to identify if this has any detrimental effect on the photos!!]. I now feel like a thorn in my side.

    I do not know how to get rid of this blemish? I am from UK.
    Have I got to contact Canon?

    Regards
    Last edited by snowshine; 6th August 2011 at 09:39 PM.

  2. #2
    benm's Avatar
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    Re: What could I do? Blemish on my EFS 18-75 mm kit lens that is 3 years old?

    Read this article first and you will see that it will probably have no effect on your photos. If you are really concerned take a photo of the defect and post it here for comment.

    http://kurtmunger.com/dirty_lens_articleid35.html

  3. #3

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    Re: What could I do? Blemish on my EFS 18-75 mm kit lens that is 3 years old?

    Quote Originally Posted by benm View Post
    Read this article first and you will see that it will probably have no effect on your photos. If you are really concerned take a photo of the defect and post it here for comment.
    I have not noticed any degradation in my photos too.


    That said all a side, I have also observed something in my work that may be worthy of note. I am by profession an Ophthalmic Surgeon, & I routinely perform cataract surgery during when put in Intra Ocular Implant Lens. From time to time some individuals will go on to develop some haziness of their vision few years following their surgery due to a thin membrane that was left in place with intention turning hazy. This thin membrane is less than mm in thickness just situated behind the Intra Ocular Implant Lens that was put in during their cataract surgery. This inserted intra ocular lens implant is a very polished biconvex lens, made of PMMA [Poly Methyl Metha Acrylic] with a built in UV filter, power varying from -2.00 dioptor to 35 Dioptors.
    To improve the vision back to their original standared, I use a LASER beam to split this membrane and in few cases few blemishes are created on the front surface of this inserted implant lens by LASER procedure -LASER induced lens scretches-craters appear but no patient is aware of any reduction in their visual quality or experiece. They do not notice glare either for a direct light source such as low direct sun in the visual axis or an artificial light source such as a torch.
    I presume that is because the blemish is more close to the anterior nodal point of a compound optical element and hence not interefered with much of the refraction induced interference.
    This may apply to EFS 17-85mm Lens too, I wonder?

    I do not know If I will be able to capture and the other lens of mine is a 30mm Sigma for my Canon 40D body.

    Thank you benm for your link and an answer.
    Regards

  4. #4

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    Re: What could I do? Blemish on my EFS 18-75 mm kit lens that is 3 years old?

    What could I do? Blemish on my EFS 18-75 mm kit lens that is 3 years old?

    This is the photo of the blemish.
    This is found on the front convex surface of the lens but deep to the front flat glass of the lens. I could not reach the surface.
    [By the way I am not an obsessional cleaner of my lens every time I use my camera.] This came to my attention through accident when inspecting my camera in sun light yesterday. Never dropped my camera in the past.

  5. #5

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    Have a guess :)

    Re: What could I do? Blemish on my EFS 18-75 mm kit lens that is 3 years old?

    Hi Arun,

    Really only a couple of choices ...

    - Either do nothing (which is "logical if it isn't having any effect on your images, albeit somewhat annoying" -- it would drive me nuts), or

    - Have it replaced (either by having Canon replace the lens element, or by buying a new lens) (upgrade?)

    Might be a good time to think about using a UV filter for front element protection if you go for option 2

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