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Re: [OM] OT; looking elsewhere

Subject: Re: [OM] OT; looking elsewhere
From: Moose <olymoose@xxxxxxxxx>
Date: Sun, 20 Feb 2011 22:10:22 -0800
On 2/18/2011 9:54 AM, Chris Barker wrote:
> Well, notwithstanding my comments to Ken a couple of days ago (about buying 
> the E-5 or going Canyon-way), I have been looking at the Pentacchio K-5.  It 
> looks smaller than the E-5, is weather resistant, has a 
> dust-shaker-offer-thingy, comes with decent lenses, has a very good review 
> from DPR and is GBP500 less than the E-5.
>
> Has anyone else had a look outside the Oly fence in this direction?

If you value the Oly "dust-shaker-offer-thingy" highly, you might want to look 
into how effective the Pentax version is. 
Early comparison tests of the others against Oly showed them to be quite 
ineffective.

I seem to recall that Pentax is one of those who vibrate their IS mechanism 
vigorously to remove dust. From an 
engineering/physics view, this is bound to be less effective than exciting the 
surface with much higher frequency sound 
than the max rate the relatively heavy IS mechanism can manage.

Not only is the frequency higher, but the accelerations are very different. 
Think of something small and sticky stuck to 
a board. Shake the board side to side at a low frequency and the effect of 
inertia in creating a force to break the 
adhesive force is sideways and relatively low.

Now imagine connecting a sound transducer to the board at a frequency 
calculated to send waves along the surface. Now, 
the force is higher, as the acceleration forward is greater and the surface 
moves back with greater acceleration. So the 
force exerted by the inertia of the glob against the adhesive strength is 
greater.

And with many sticky thingies, there is a tendency to roll under sideways 
force, breaking adhesion on one side as new 
contact on the other creates new adhesion. With vertical force, that doesn't 
happen.

Or maybe put a booger on your finger. Wave from side to side, then snap hand 
forward and back as quickly as you can. 
Booger on the wall now? :-)

OK, maybe that's better as a thought experiment, too.

Moose
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