[manntax]

From what I understand, when one zooms a lens, air is pumped in and out of it. This will eventually bring in fine dust. I suspect even focusing would do the same to a lesser extent.

I never though of zooming moving air, but it's entirely common sense.
My shiny new q7 lens looks horrible with a torch, but I'm still a happy bunny :-)

Jeff

As far as I know it has nothing to do with zooming action or focusing - especially that brand new and unused lenses has this microscopic particles inside. What we talking about is often glass itself which contains micro-micro scopic contamination and also during production process they are unable to filter out *everything* - up to certain size yes - but anything smaller will get through and can enter the space between the glass elements. These particles are invisible to the eye in normal conditions. I advise anyone who is in doubt to take a brand new, shiny, unopened and unused lens and backlight it with flashlight - I guarantee that it will look similar. But we talking about particles entirely invisible to the eye so when one is looking through the lens it IS absolutely clean - even against the light. Only a strong beam of light and at a certain angle will reveal these particles that due to reflections becomes visible.

Absolutely normal and expected --manntax