Sensor cleaning mode maps out hot pixels

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?

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.

" 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?

--
Måns Rullgård

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.

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."

--
Transpose mxsmanic and gmail to reach me by e-mail.

In article , Måns Rullgård
writes
" 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)

In article , Mxsmanic
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)

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.

Måns Rullgård wrote:
" 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?

It replaces their data with data from spare pixels around the edge of
the sensor. Have you ever noticed how cameras are spec'd as having
a certain number of actual pixels and a slightly smaller number of
"effective" pixels. The difference between the actual and effective
pixel count is made up by the spare pixels around the edge. You'd
think that it would be easier to remap photons to a spare pixel that
was near the pixel it replaces. Researchers have discovered, much
to their surprise, that distributing the spare pixels thoughout the
sensor disrupts the final image. So instead they employ some fancy
optical footwork to redirect the hot pixel's photons to a spare
that's out of the way at the edge of the sensor. Neat, huh?

Paul Allen

In article om,
" writes

But why would Canon not document
this feature? One reason is given in the link below but it makes no
sense IMO;

Canon choose not to document a huge number of "features". For example,
there isn't one single official Canon documentation of how their flash
system works - only unofficial, mainly composed of rumour, experiment,
trial and error and reverse engineering descriptions. In terms of
documentation they are almost as bad as Sony, if that were possible! ;-)

I wouldn't rely on lack of documentation as a reason to discount a
feature.
--
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)