> > From: Cotty <[EMAIL PROTECTED]> > Date: 2005/09/06 Tue PM 06:46:14 EDT > To: "EOS list" <[email protected]> > Subject: Re: Wide-angle & DSLR (was: EOS Moving to Canon for Digital > > On 6/9/05, Huber, Richard, discombobulated, unleashed: > > >I seem to remember a complaint by several people that the zooms cause > >MORE dust on the sensor than the primes. Evidently, by changing the zoom > >length, the influx of air and dust went straight to the sensor on taking > >a photo. Whereas a prime, once attached does not continually draw in, or > >expel air from the mirror cavity. > > IIRC all lenses move elements internally to focus. By design, they are > effectively weak air pumps. If the physical size of the lens changes a > lot when focussing, then perhaps not so weak a pump..... > > > > > Cheers, > Cotty > > > ___/\__ > || (O) | People, Places, Pastiche > ||=====| http://www.cottysnaps.com > _____________________________ > That would be the 100-400 f4.5-5.6 L IS USM. Its pushme/pullyou design seems optimal for pumping air in and out. But I wonder how much air gets past the rear element, on any lens, including that air pump...
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