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Fungus/Oil/Glue? Canon EF 70-200mm f4 L IS II USM Lens


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Recently I bought a Canon EF 70-200mm f4 L IS II USM Lens in fantastic condition on eBay. However after inspection noticed some kind of residue or something within the elements of the glass? It doesn't effect the image but does raise slight concern. No sign of any previous fungus on the glass optics just this strange white residue around the edges.

 

Does anyone know what it is, and if it's to be concerned about?

 

i01_IMG_20210202_141901__01.jpg

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It might be black paint flaking off or the lens element separating a tiny bit from the barrel in which it sits. This happens due to lenses being exposed to high heat; the metal barrels will expand slightly and the glass won't expand at the same rate. Think, leaving the camera bag in a car trunk in the summer. If the lens makes a good image, it's nothing to worry about. The separation that you may be seeing is almost immeasurable. Usually lens elements and groups will be coated with a flat black paint on their edges. When the paint separates, bubbles or completely flakes away, what you can see is the frosted edge of the lens element from the inside. Your lens is probably in otherwise fine condition and even sending it off to Canon probably wouldn't make a difference.

Phil Forrest

Edited by Philip Forrest
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