Canon 100mm f2.8 L is owners, dust circle inside lens?

[fohtohz]

Hi all, I just got a 100L and was looking down the front of the lens through to the rear under a light and noticed what seems to be a weird circle of stain or dust on the inside of the lens(around the edge and 2/3s near back element), was wondering if anyone with the same lens has the same thing.

This lens is supposed to be weather sealed and the stain is not on the back element, so was wondering what it was. Apart from this strange circle, everything functions great, maybe it's a reflection off something. thanks

[iaind]

Had mine for 18 months and still dust free

[fohtohz]

mine doesn't really have dust, it's more like a circle of gray stain or glue on the outer edge inside the lens itself, it doesn't show looking from the rear element, only when looking from the front with a light and with aperture blade wide open.

have to look carefully, no one else has this??

[ideaworx]

All clear here, not seeing this ring

[neuroanatomist]

No 'ring' except I do see the edge of the iris diaphragm.

[imkev]

Mine looks clean too...Might want to think about swapping it out if you just got it.

[swrightgfx]

Is it fine white powder? (No, I am not implying Canon or the retailer are involved in drug trafficking!)

I have seen this before. It is from some sort of low-density plastic or rubber, from what I gather, probably as an agent to keep it dry enough not to harbour fungus (think talc). From what I have read, it being of the amount that it is visible is rare (perhaps limited to a particular batch), but is also quite stationary and "stuck" to the surface upon which it sits. I guess it isn't a good idea to throw your lenses around, which would likely loosen it, but that probably applies white dust or not.