Question about Canon 75-300mm f/4-5.6 III USM EF Lens

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I have dust under outer lens on my 75-300mm f/4 -5.6 III USM

I keep having a dust spot on my pictures so afters lots of cleaning and trying it over and over, I found the dust but it is under the lens, I think I can just unscrew the 3 little screws and use my blower to remove it then replace the screws, but not sure what would happen do things need to be aligned? with it still make nice photo's any ideas kinda of nervous to just started taking things apart

thanks
Justin

Posted by on

  • Anonymous Mar 21, 2009

    I was about to give away an old Canon zoom lens ef 75-300mm 1:4-5.6 II that I couldn't seem to dismantle to clean until I read this. Thanks guys!!!

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Front element? You can remove this without alignment worries. The lens zoom mechanism tends to **** in the dust.

Have a look at the front element outer ring. There are 3 black screws. Remove these using jewellers screwdriver (y'know, a very small posi-drive one!). Remove this plastic outer ring. Now you can see three small silver screws, that are about the same size - when you try to unscrew them, they just rotate...

This is as they are not screws, but as mentioned elsewhere - they are plugs (if you notice, they are slightly under the casing. Get a small flat bladed screwdriver, and gently prise them out. Now you can just drop the front element into something sensible - like a microfibre cloth (give it a clean whilst you're there.

Get a rocket blower (NOT canned air), and blow away the dust, and you can use the microfibre cloth (or similar) on the small inner front element.

Then replace the outer front element - you will see where it drops into place - there are plastic guide tabs. Push back the silver 'screw' plugs.

Then screw back on the plastic outer ring and you're done - takes 20 minutes at the most.

Posted on Jul 30, 2009

  • Megan
    Megan May 20, 2014

    how do you remove these small plugs aside from the flat screw driver?

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Well I just found that the y are not screws but plugs, and if you use a small screw driver you can pull them out and th elens drops out . Now all I need is some pne to tell me how to get the outer case off the inner.

Posted on Jul 29, 2008

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If you wish to attempt that, there are other steps involved before removing the 3 screws. The circuit connection is attached to the mount ring, held by 2 screws in the channel of the mount. You may need to free the center plastic on the mount to remove the ring itself. ( I am going from memory, I don't have a lens on hand to look at )

Posted on Jul 08, 2008

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