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Sensor cleaning mode maps out hot pixels

 
 
oparr@hotmail.com
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      03-31-2006
There seems to be a popular belief on http://www.dpreview.com/forums/
that the Canon 5D and 30D will map out hot pixels when one goes into
sensor cleaning mode. This sounds more like an April fool's joke to me.
Does anyone here have any credible information on this?

 
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Jim Townsend
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      03-31-2006
http://www.velocityreviews.com/forums/(E-Mail Removed) wrote:

> There seems to be a popular belief on http://www.dpreview.com/forums/
> that the Canon 5D and 30D will map out hot pixels when one goes into
> sensor cleaning mode. This sounds more like an April fool's joke to me.
> Does anyone here have any credible information on this?


All Canon's sensor cleaning mode does is lift the mirror and open
the shutter blades so the sensor is exposed. (It would be mighty
hard to clean the sensor otherwise



 
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oparr@hotmail.com
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      03-31-2006
Jim Townsend wrote:
> All Canon's sensor cleaning mode does is lift the mirror and open
> the shutter blades so the sensor is exposed. (It would be mighty
> hard to clean the sensor otherwise


In other words as far as you know it does no more than the above on a
5D or 30D? Do you have either of these cameras? I have two D60s and a
20D and know what sensor cleaning mode does on them. I don't have a 5D
or a 30D.

 
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=?iso-8859-1?Q?M=E5ns_Rullg=E5rd?=
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      03-31-2006
"(E-Mail Removed)" <(E-Mail Removed)> writes:

> Jim Townsend wrote:
>> All Canon's sensor cleaning mode does is lift the mirror and open
>> the shutter blades so the sensor is exposed. (It would be mighty
>> hard to clean the sensor otherwise

>
> In other words as far as you know it does no more than the above on a
> 5D or 30D? Do you have either of these cameras? I have two D60s and a
> 20D and know what sensor cleaning mode does on them. I don't have a 5D
> or a 30D.


How could it possibly do anything about hot pixels?

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Måns Rullgård
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ASAAR
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      03-31-2006
On Fri, 31 Mar 2006 19:37:28 +0100, Måns Rullgård wrote:

>> In other words as far as you know it does no more than the above on a
>> 5D or 30D? Do you have either of these cameras? I have two D60s and a
>> 20D and know what sensor cleaning mode does on them. I don't have a 5D
>> or a 30D.

>
> How could it possibly do anything about hot pixels?


Some cameras need to be returned to the manufacturer to map out
hot pixels. Others (such as some Olympus models) allow it to be
done by the user - it's a menu option. If Canon wanted to allow
their 5D or 30D models to map out hot pixels it could easily be
added as a menu option, but one can safely assume that it wouldn't
be added as an unannounced side-effect of a sensor cleaning mode. I
would like to have been able to say that Canon maps out hot pixels
whenever histograms are enabled or the 5D's hidden flash is
extended, but it's not yet April 1 on this part of the globe.

 
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Mxsmanic
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      03-31-2006
ASAAR writes:

> Some cameras need to be returned to the manufacturer to map out
> hot pixels. Others (such as some Olympus models) allow it to be
> done by the user - it's a menu option. If Canon wanted to allow
> their 5D or 30D models to map out hot pixels it could easily be
> added as a menu option, but one can safely assume that it wouldn't
> be added as an unannounced side-effect of a sensor cleaning mode. I
> would like to have been able to say that Canon maps out hot pixels
> whenever histograms are enabled or the 5D's hidden flash is
> extended, but it's not yet April 1 on this part of the globe.


If the sensor is of decent quality, there are no hot pixels to "map
out."

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Kennedy McEwen
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      03-31-2006
In article <(E-Mail Removed)>, Måns Rullgård
<(E-Mail Removed)> writes
>"(E-Mail Removed)" <(E-Mail Removed)> writes:
>
>> Jim Townsend wrote:
>>> All Canon's sensor cleaning mode does is lift the mirror and open
>>> the shutter blades so the sensor is exposed. (It would be mighty
>>> hard to clean the sensor otherwise

>>
>> In other words as far as you know it does no more than the above on a
>> 5D or 30D? Do you have either of these cameras? I have two D60s and a
>> 20D and know what sensor cleaning mode does on them. I don't have a 5D
>> or a 30D.

>
>How could it possibly do anything about hot pixels?
>

Relatively easily. Other cameras have a hot pixel mapping capability
already.

All it needs is a dark frame to be captured and then pixels above a
certain threshold value to be mapped out as hot by the processor.
Ideally the dark frame would be a reasonable length exposure.

The Canon 5D has a 2-3second delay between pressing "OK" on the sensor
clean dialog and the shutter actually opening that other Canon cameras
don't seem to have, which suggests something is being done. This would
certainly be a suitable time to implement the entire expose-mapping
process.

I haven't seen any hot pixels on my 5D to be able to check if this is
true, but at the same time I wouldn't rule it out. Borderline pixels
are likely to be more of an issue as pixel count increases, so the
introduction of some in-camera process to deal with them on high
resolution cameras shouldn't be too surprising.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
 
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Kennedy McEwen
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      04-01-2006
In article <(E-Mail Removed)>, Mxsmanic
<(E-Mail Removed)> writes
>
>If the sensor is of decent quality, there are no hot pixels to "map
>out."
>

Really? Do the arithmetic. The current industrial maxim for
"perfection" is six-sigma. That corresponds to 3.4 defects in every
million units produced. To put it in perspective that means a service
outage of less than 20 minutes every ten years for telecoms, power or
broadcast systems. Few manufacturers or delivery systems actually
achieve it, but it is a valid aspiration.

In terms of sensor in digital cameras, six sigma is 3.4 defective pixels
per megapixel. So in 12.8million pixels, best practice standards would
result in an *average* of 44 hot or cold pixels in each sensor produced.

You can certainly buy sensors with no "hot" pixels to map out, but I am
fairly confident that you are unlikely to earn enough in you entire
working life to afford one! So your body will be in a rather indecent
state before you'll ever own what you consider to be a "decent quality"
digital camera!
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
 
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oparr@hotmail.com
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      04-01-2006
Here's a link to a post supporting the claim;

http://forums.dpreview.com/forums/re...ssage=16851724

In fact that thread and that thread alone is the basis of the claim.
30D claims reference the above.

 
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oparr@hotmail.com
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      04-01-2006
>All it needs is a dark frame to be captured and then pixels above a
>certain threshold value to be mapped out as hot by the processor.


Yes it's feasible that sensor cleaning mode could be used to map out
pixels that become hot after a second or two. It would then be left up
to the user to turn on NR (dark frame noise reduction) to handle any
after a second or more if necessary. But why would Canon not document
this feature? One reason is given in the link below but it makes no
sense IMO;

http://forums.dpreview.com/forums/re...ssage=17838784

Kennedy McEwen wrote:
>


 
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