Strange spots behind front lens of EF17-40mm

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Fotookes New Member • Posts: 13
Strange spots behind front lens of EF17-40mm

Hi Everyone,

I recently pulled out my venerable EF17-40mm wide angle lens from storage and was a bit shocked to notice multiple small spots behind the front lens element! This is not mould nor dust, but seem to be consist of 'flakes' of some kind. Could it be that the coating of the front lens or the one behind it (from the optical design it seems like there are two elements in the first, front, group) has started to break up and that these flakes are the result?

Usually a little dust wouldn't bother me much, have some really old Pentax lenses with a lot of dust inside which doesn't harm at all, but if the coating of the big front lens element is breaking up, especially on a wide angle (tele would be less of a problem?)

For your reference: there is one internet posting with pictures of the problem you can easily find under the name "strange spots on the front lens of my ef17-40mm"!

The person who posted it didn't know what the cause was, he just illustrated his attempt (failed!) to disassemble his lens in order to clean it, but had to give up because the front element was clearly part of a group and could not be cleaned individually.

For those wondering, I did shoot a few shots to test, but do not have anything big screen with me on this trip, so cannot really judge much if anything is bad, image quality wise!

Thanks for any helpful feedback!

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