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  1. #1

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    Canon Lens Coating Issue

    I'm looking to buy a Canon 70-200 f4L from a co-worker but the lens has some weird spots on the front glass (the protective "filter"). I suppose I could get that glass replaced but anyone have any idea what's causing this?

    THanks,
    Dan
    Attached Thumbnails Attached Thumbnails IMG_8347.jpg  

  2. #2
    hoffy's Avatar
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    I'm no expert, that looks nearly organic. I won't say fungus....yet, as the fungus I have seen looks a bit more spider webby

  3. #3

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    Some kind of etching ?
    Is it realy on the front surface of the frontlens ?
    Having the frontlens replaced could be a tad expensive and I wonder if you would see any effect of it on your photo's.....

    Put it onto your camera and see what kind of result you get and if it does not show up at high maginification get it for cheap.

    Peter

  4. #4
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    Hello fungus my old friend....

    Try keeping the lens on a sunny window sill for as long as possible (weeks, months) to kill/stop the growth.
    Try to determine if any inner elements are affected.
    Get an estimate for a clean-up.

    A good way to bargain the price down, though.
    M6, SL, SL2, R5, P6x7, SL3003, SL35-E, F, F2, FM, FE-2, Varex IIa

  5. #5
    hoffy's Avatar
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    As I thought. Fungus is treatable and if caught early enough will not damage the lens.

    I have just had one cleaned from fungus. It was there and it was not overly big. It cost me $45Aust. I have to admit, I haven't seen a lens element as clean as the job that I had done!

    Mind you, this was an enlarger lens. I could imagine a 70-200L might cost a tad more, especially if then need to get down to the nitty gritty

  6. #6
    Rol_Lei Nut's Avatar
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    I've had several lens with fungus like yours and most cleaned up nicely. Even the worst cases (within reason, when the fungus looked a bit like yours - I've seen lenses which looked like someone had stuffed a cotton ball inside) left tiny specks on the coating which are insignificant as far as the image is concerned.

    In some cases, though, the fungus returned after a few years and those lenses are on my windowsill again...
    :-(

    Incidentally, they seem to be the lenses which have gotten the least use, so maybe regular use lets through enough UV rays to keep things under control.
    M6, SL, SL2, R5, P6x7, SL3003, SL35-E, F, F2, FM, FE-2, Varex IIa

  7. #7
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    Looks like some kind of fungus/etching which you can definitely use as a bargaining point.

    It won't affect image quality with the way it is now. Atleast, not in any way you'll be able to spot with your own eyes.
    Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.

    http://www.flickr.com/kediwah

  8. #8
    Rol_Lei Nut's Avatar
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    Quote Originally Posted by clayne View Post

    It won't affect image quality with the way it is now. Atleast, not in any way you'll be able to spot with your own eyes.
    Here I have to disagree... Uncleaned, that kind of fungus will affect the lens' transparency and lower the contrast, especially in flare-type situations.

    Cleaned, I agree that it will not affect quality.
    M6, SL, SL2, R5, P6x7, SL3003, SL35-E, F, F2, FM, FE-2, Varex IIa

  9. #9

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    I was afraid it was fungus. I don't think the lens has been used much, if at all, for the past few years. I tried it out over the weekend and it yields nice images - whether there's degradation due to those spots, I couldn't say though. The reason I'm looking to buy the lens is to take on a trip to Rocky Mountain National Park in two weeks (instead of my 70-200 f2.8L IS, which I don't want to leave in the car while hiking, and which is too heavy to carry on some of the hikes we're planning). I'm thinking this lens is still better than Canon's 100-300 f4.5-5.6 (which I can pick up from KEH in EX+ for around $150). What do you think is a fair price for it in its current condition?

    THanks,
    Dan

  10. #10

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    You might try cleaning it off with some ROR (Residual Oil Remover) which should be available at a good camera store.

    I cleaned fungus spots like those off the front element of a Minolta lens using plain white vinegar. It did a great job. I followed that cleaning with a more routine cleaning to get rid of any possible vinegar residue. I, however, cannot recommend you use this because the vinegar may, since it is acetic acid, be harmful to the lens coating. It didn't hurt that old Minolta lens but I would hesitate before I used it on one of my newer Canon or Nikon lenses.

    Once you get it clean, make sure you store the lens properly. If you keep it in a case or bag, make sure you keep a bag or two of desiccant in with it.

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