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12-03-2010, 04:47 PM   #1
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WR - more than weather benefits?

At first glance, the WR attributes of the Pentax lenses seem to revolve around weather; usually wet weather or snow. When considering the value of WR it's useful to expand the thinking to a more varied environment.

While the WR seals aren't absolutely pressure tight, they do serve as a filter against airborne particles and act as a buffer against rapid changes in the pressure differential and temperature between inside and outside of the lens (and the body, too).

I recently had the opportunity to ferry a small, unpressurized aircraft from near Reno, NV to northwestern Tennessee. Over the course of three days a K100DS with the DA 18-55WR experienced effective pressure changes from slightly below sea-level to 10,000 feet relative to pressure altitude. Rapid pressure altitude changes of as much as 7,000 feet in about half an hour were common -- that's the sort of change that repeatedly pops your ears and isn't normally experienced in land transportation vehicles.

[ Special Kit Decisions - Aviation! - PentaxForums.com ]

It's accepted that zooming a lens pumps air (and dust and humidity) into and out of the lens barrel. Even focusing and the expansion and contraction associated with temperature changes has some small but detectable effect.

I chose to carry the DA 18-55WR specifically because I felt the WR seals would either eliminate or at least slow the flow of air in and out of the lens and camera mount.

Did one three-day trip make a difference? I don't know. Over time though, it makes sense that minimizing the exchange of air and airborne particles with the WR seals must have a beneficial effect.

And shooting through old Plexiglas windscreens certainly negated any value of higher definition glass.

Since dust and humidity are factors in fungus, it may be that WR has benefits beyond the obvious.

H2

12-03-2010, 05:31 PM   #2
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QuoteOriginally posted by pacerr Quote
Since dust and humidity are factors in fungus, it may be that WR has benefits beyond the obvious.
Certainly - but what's really going to save you in the long run is internal focusing (which many WR lenses already have), no moving external parts (i.e. DA 18-135 focusing vs DA 17-70 focusing) and internal zooming (something only found on select zooms):

The 50-135mm immediately comes to mind as a lens that fits all of these categories, and as it's also a weather-sealed lens, it's THE ideal choice for bad weather or simply to be a workhorse!

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12-03-2010, 05:46 PM   #3
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The sealing on the da18-135 has an additional reward I have never seen mentioned. The air seal is just right so that when I zoom in then quickly back out, it WHISTLES! If I can learn to modulate the whistle it and play a tune it will be my first K-5 video posted.
12-03-2010, 05:48 PM   #4
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QuoteOriginally posted by Adam Quote
The 50-135mm immediately comes to mind as a lens that fits all of these categories, and as it's also a weather-sealed lens, it's THE ideal choice for bad weather or simply to be a workhorse!
Does the 16-50 fit all of these categories too?

12-03-2010, 07:19 PM   #5
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QuoteOriginally posted by psychdoc Quote
Does the 16-50 fit all of these categories too?
The 16-50 is internal focusing, but not internal zooming.
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