Archived posting to the Leica Users Group, 2007/01/21

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Subject: [Leica] Re: LUG Clean that M8 sensor?
From: red735i at earthlink.net (Frank Filippone)
Date: Sun Jan 21 17:11:08 2007
References: <012220070031.4012.45B405F20007842100000FAC219792474103010CD2079C080C03BF970A9D9F9A0B9D09@mchsi.com>

Cell sizes ( in the order of a few microns)  would be too small to take on 
much charge....  capacitors are really tiny.... yes, they
hold a residual charge but it is small....  You would need a pretty good 
charge to attract and hold onto a physical particle.  

Ok,,,, as a kid ( circa 50's and 60's) watching ... what was his TV name, 
Dr. Science?  Something like that.....experiments with
charge and of course, shocking others, I remember the relationship of 25,000 
volts per inch of charge necessary to generate a spark,
using your wool socks on the floor. Later, there was the comb in the hair 
trick where your hair would stand on end..... again, a
charge of several thousand volts.   IC circuits have breakdown voltages of a 
few tens of volts, or less.  Getting a sizeable charge
on device would destroy the device.

Thinking about it in another way, there is no way it is the sensor.  The 
sensor is not available to the dust.  The cover plate is
the thing that is open to the environment......  It is possible that the 
sensor cover plate is picking up a charge.....  ( See your
TV, CRT or LCD screen for a demonstration of dust pickup....).  Glass is a 
fairly good insulator, and you need that to make a
capacitor or a "charged device".  However, this charge is not a function of 
circuit power.  Turning off the power does nothing to
cut the charge. 

It seems strange that the Canon instruction manuals and  the M8 instruction 
manual has no reference to this ..... shutting off power
to keep dust from sticking to your sensor (cover).....   Neither tells you 
to shut off power when changing lenses.....

I'm still unconvinced.... a reference that explains the physics would be 
handy, or a reference by a sensor maker would help.....
I am still in favor of the new wives tales told by sensor cleaning product 
makers.....  Maybe Fred Picker has come back to create
new Digital Photo Truths?

But it does no harm..... so keep doing it.....if you want.....


Frank Filippone
red735i@earthlink.net 

The devices must have enough energy stored up to create/record the images, 
this comes from energy stored by capacitors in the
circuit, this energy can indeed be enough to attract dust.

Gene



In reply to: Message from grduprey at mchsi.com (grduprey@mchsi.com) ([Leica] Re: LUG Clean that M8 sensor?)