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Sensor cleaning mode maps out hot pixels

 
 
Kennedy McEwen
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      04-01-2006
In article <(E-Mail Removed)>, Mxsmanic
<(E-Mail Removed)> writes
>Kennedy McEwen writes:
>
>> Really? Do the arithmetic.

>
>Skip the arithmetic. Do the economics.


You should. Current prices for a defect free APS-C sensor are so high
that they do not even feature in the standard price lists from sensor
suppliers!
>
>> 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.

>
>The telephone companies achieve it.


No they don't. Telephone companies will frequently have outages of more
than 20 minutes on any line over a ten year period.

> Disk drives achieve it.


No they don't. Disk drives have the faulty sectors mapped out at the
factory.

>Electronic memory modules achieve it.


No they don't - same as above.

> Good flat-panel monitors
>achieve it.
>

No they don't. Flat panel monitors require a test and repair process
prior to shipping to fuse existing faulty pixels and fabricate ITO
conductors and replacement transistors on the cells which are found to
be faulty at manufacture. It was the development of this process which
made flat panel displays a viable option in the first place.

>> 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.

>
>That would also mean seven bad pixels in a 1600x1200 monitor, which is
>far above what the good monitors actually show (many have no bad
>pixels at all).
>

That is correct - for the reasons that the pixels on your monitor are
about 50-100x larger than those in your sensor and are manufactured in a
technology which is amenable to fixing single pixel faults economically
at manufacture. It is not a solution that is available for sensors, nor
does it need to be, since a hot sensor pixel can be electronically
concealed whilst a display pixel cannot.

>> 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!

>
>I'm not. They aren't that expensive, although they are more expensive
>than defective sensors.
>

Find me a single supplier of sensors larger than half a megapixel which
will even quote a defect free sensor on their standard price list.

> If you're paying $8000 for a camera body,
>it's entirely reasonable to expect zero defective pixels. If you're
>buying consumer junk, obviously all bets are off.


$8000 for a camera body probably means a cost of less than $4000, with a
sensor cost of half that. $2000 wouldn't even get you a full frame HG
(high grade) sensor which is the highest standard priced product. In
most cases it would land you squarely in the middle of the IG
(industrial grade) range, but I doubt that even many professional dSLRs
have better than EG (economy grade) sensors in them.
--
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) .com>,
"(E-Mail Removed)" <(E-Mail Removed)> writes
>>Canon choose not to document a huge number of "features".

>
>It's as though one is supposed to either disbelieve
>or take a leap of faith and believe.
>

You can always "test and believe", which appears to be what has
initiated the rumour in the first place. As I have previously said in
this thread, I wouldn't rule it out but neither will I necessarily
believe it until such times as I have had the opportunity to test it.
That means I need to find suitable unmapped hot pixels in my 5D to begin
with, and at the moment there aren't any.

Perhaps during the heat of summer or my upcoming trip to Florida a few
will appear enabling such tests to be undertaken.
--
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 <Xns9797DD9EBE447samthemanverizonnet@199.45.49.11> , SamSez
<(E-Mail Removed)> writes
>
>[in your little mind perhaps...]


No, in a perfectly logical operational procedure. Only in "your little
mind" would it appear to be impossible.
--
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)>, Måns Rullgård
<(E-Mail Removed)> writes
>
>I know how hot pixels can be dealt with. Lifting the mirror and
>opening the shutter is certainly not going make finding them any
>easier.
>

*Nobody* is even suggesting that "lifting the mirror and opening the
shutter" helps mapping dead pixels. What *is* being suggested is that
Canon have introduced and undocumented step in their sensor cleaning
procedure which maps dead pixels *before* raising the mirror and opening
the shutter.

Go into any store and compare the time for a 20D and a 5D to open the
shutter after selecting the "sensor clean" operation on the menu. the
20D is almost instant, the 5D delays for a few seconds - so long, in
fact, that the first time I tried this on my 5D I thought the software
had crashed and it wasn't going to open the shutter for cleaning at all!
Canon have clearly changed the procedure between these two models being
introduced. There could be a number of reasons for the change, only one
of which is hot pixel mapping. Perhaps the full frame sensor requires
to be powered down slowly to avoid static charges being left on the
sensor surface which would certainly cause problems when cleaning.
Nobody knows - but hot pixel mapping could certainly be done in the time
the camera appears to be doing nothing else but dozing.

Without actually testing for the change in hot pixel presence before and
after the operation it isn't possible to say one way or the other
whether the 5D maps out hot pixels during that time, however it
certainly isn't possible to discount it.

Those who *have* had the opportunity to test appear to be confirming it
though - albeit a small number. That small number is, however,
significant since only a small number of people should be getting
unmapped hot pixels in the first place. In contrast, the group
discounting the claim appears to comprise *only* people who have had no
opportunity or interest in testing the situation at all. That is simply
illogical - without test, the claim can neither be discounted nor
substantiated so the group who have not tested *can* only be open minded
or stupidly prejudiced (one way or the other) on the matter.
--
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
> No, in a perfectly logical operational procedure.

I sent Canon the following enquiry;

"I'm thinking of getting either a Canon 5D or 30D and would like to
know whether any of them is capable of mapping out hot pixels on its
own like some Olympus DSLRs."

It will serve as the official word for me even if their reply is
incorrect. Surprsing that none with these cameras ever came forward
with "According to Canon..." on this issue. They seem to run to Canon
over just about everything else and Canon's word is always gospel to
them.

Kennedy McEwen wrote:
>


 
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Kennedy McEwen
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      04-01-2006
In article <(E-Mail Removed) .com>,
"(E-Mail Removed)" <(E-Mail Removed)> writes
>> No, in a perfectly logical operational procedure.

>
>I sent Canon the following enquiry;
>
>"I'm thinking of getting either a Canon 5D or 30D and would like to
>know whether any of them is capable of mapping out hot pixels on its
>own like some Olympus DSLRs."
>
>It will serve as the official word for me even if their reply is
>incorrect. Surprsing that none with these cameras ever came forward
>with "According to Canon..." on this issue.
>

Because stock answers do not address undocumented features.

> They seem to run to Canon
>over just about everything else and Canon's word is always gospel to
>them.


Rubbish. Canon's response to question on how flash exposure is computed
in their TTL metering derivatives has been negligible. The unofficial
description of the process at phtonotes.org runs to over 75 pages of 10
point text, only one of which appears to have even semi-official
heritage. So Canon's word certainly isn't gospel on that undocumented
topic to any EOS user.
--
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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Bill Funk
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      04-01-2006
On Fri, 31 Mar 2006 22:10:30 +0200, Mxsmanic <(E-Mail Removed)>
wrote:

>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."


Do you work for Microsoft?
I ask, becasue your answer, while undoubtedly right, is useless.
--
Bill Funk
replace "g" with "a"
 
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oparr@hotmail.com
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      04-01-2006
> Rubbish. Canon's response to question on how flash exposure is computed
> in their TTL metering derivatives has been negligible.


I couldn't care a rat's ass about the details of ETTL1 or ETTL2. They
both work fine for me. However, I would like to know whether going
forward hot pixels will or have become a non-issue with Canon's DSLRs.
You're saying I'll never know from asking Canon based on experience
with something else. For crying out loud...They haven't even answered
me yet.

Kennedy McEwen wrote:

> Because stock answers do not address undocumented features.


 
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ASAAR
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      04-01-2006
On Sat, 1 Apr 2006 13:47:49 +0100, Kennedy McEwen wrote:

> Go into any store and compare the time for a 20D and a 5D to open the
> shutter after selecting the "sensor clean" operation on the menu. the
> 20D is almost instant, the 5D delays for a few seconds - so long, in
> fact, that the first time I tried this on my 5D I thought the software
> had crashed and it wasn't going to open the shutter for cleaning at all!


Maybe the 5D is the first Canon that uses a version of MS's
Portable Windows for its OS? <g>

 
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Kennedy McEwen
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      04-01-2006
In article <(E-Mail Removed) .com>,
"(E-Mail Removed)" <(E-Mail Removed)> writes
>> Rubbish. Canon's response to question on how flash exposure is computed
>> in their TTL metering derivatives has been negligible.

>
>I couldn't care a rat's ass about the details of ETTL1 or ETTL2. They
>both work fine for me.


So why should you give a rat's ass about whether hot pixels get mapped
out in the sensor cleaning procedure or not? All that matters is that
hot pixels are controlled by some means or another - whether that is by
mapping them through an undocumented feature, in-camera processing or
manufacturing controls in the factory makes no difference. If hot
pixels concern you, why is Canon's response on only one means of dealing
with them at all relevant? They already deal with them quite
effectively at shutter speeds of longer than 1sec by enabling in-camera
dark field subtraction (details also undocumented) in custom function
CFn-02.

>However, I would like to know whether going
>forward hot pixels will or have become a non-issue with Canon's DSLRs.


They *are* a non-issue - otherwise I, and countless others, would
already be able to answer your ludicrous question immediately. Perhaps
you haven't been reading - the reason I can't say whether the claims are
true or false is because I don't have hot pixels to clear.

>You're saying I'll never know from asking Canon


Actually, I wasn't the first to say that - you were! You wrote:
"It will serve as the official word for me even if their reply is
incorrect." Why is the official word so important to you when you
accept that it could, and in the case of undocumented issues probably
will, be wrong?

>based on experience
>with something else.


That "something else" demonstrates that they rarely comment on
undocumented processes or procedures, and when they do it is usually
just a summary of what is already documented. There are good economical
reasons why this is the case - generally the same reasons why the issues
are undocumented in user information to begin with!

So ultimately, the only response that matters from Canon is if they
confirm the claim, since a denial could merely be continuance of company
policy on undocumented features and you have not asked what is actually
going on during that long delay between "OK"ing sensor clean and the
shutter opening.
--
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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