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KulaCube Jul 31, 2011 1:43 PM

Zooms -- a mechanical question
Just purchased the 40-150 M. Zuiko. Was playing with the lens prior to mounting it on my pl1. Noticed a "woosh" of air as it zoomed from long to wide. Coming from the mount end. Having only used primes in the past, never thought about this.

If the lens doubles the interior volume as it increases in length, then either air must be allowed to enter or they have to build it very strong to take into account interior pressure changes. And if air is designed to get in, then so will dust etc. Then gets released through the mount end -- guessing through the zoom barrel ring. I realize a small amount of dust in the interior should not drastically alter the image quality. But I can now understand the benefit of going to the "high grade" lenses.

Ozzie_Traveller Jul 31, 2011 4:29 PM

G'day KC

Your observations are 100% spot on - and "not to worry, she'll be right mate"
Every mechanical item needs some {microscopic} slack space so that movement can take place (think of your tripod legs sliding inside one another), and a camera lens is no different

Some very expensive pro-quality lenses are 'enviro-sealed' and they are dust proof & water proof, and that brings its own issues. However, our consumer level 'day-to-day' lenses will, over time [5-10 years] allow some very tiny dust elements into the lens

Is it a worry & all that ??? .... Not in my opinion

I have used 2nd-hand lenses after 10yrs of someone else's use, inside the lens barrel, looking at the front-inside glass elements I can see 10-20 tiny dust spots, and photographically I cannot see any issues with image quality

"Maybe" if I was a pro-'tog and producing material of 1,5metre x 3metre sizes, it would be an issue, but for 4" x 6" to 12" x 18" .... not something to worry over

Hope this helps
Regards, Phil

KulaCube Aug 2, 2011 5:16 PM

Thanks Phil
T'was more of an observation than a worry. It caught me by surprise when I first felt the whoosh. So I will keep the beasty sheltered from dusty environments (like our backyard with the construction going on behind our fence) and have fun exploring the abilities and options this lens offers

JeannieBug Aug 2, 2011 5:44 PM

If only I could keep mine out of dusty environments!

Ozzie_Traveller Aug 3, 2011 4:36 PM

G'day KC

Dunno what it's like up your way, but down here in the Oz outback we have a condition known as "bull-dust" ... a fine powdery dust just like talcum powder. As one travels thru the outback, it gets into everything - doors, windows, air vents in the vehicle etc etc. Run your hand over a table surface, you can feel it but it's too small to see till you look at your hand

It also gets into precision equipment [cameras & lenses in our case] and makes life difficult too, shortening the life of lots of things with moving parts

Regards, Phil

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