20D hot pixel

Archived from groups: rec.photo.digital.slr-systems (More info?)

I got one white hot pixel. Should I bother to exchange it? How many
people have got a perfect sensor? My last Digital Rebel (2nd one
actually, the first one was exchanged for another reason and I didn't
doa pixel test) had no dead/hot pixels. Thanx.

Archived from groups: rec.photo.digital.slr-systems (More info?)

Depends on when you get it. If you get it with long exposures it is pretty
much par for the course. Try turning on the special long exposure noise
reduction in the camera and see if that helps.

If it is regular length exposures (any thing faster than 1 second) I would
exchange it as you shouldn't have it showing with those types of images.

John


"leo" <someone@somewhere.net> wrote in message
news:cq095b02h16@news1.newsguy.com...
>I got one white hot pixel. Should I bother to exchange it? How many people
>have got a perfect sensor? My last Digital Rebel (2nd one actually, the
>first one was exchanged for another reason and I didn't doa pixel test) had
>no dead/hot pixels. Thanx.

Archived from groups: rec.photo.digital.slr-systems (More info?)

At 1/60th of a second I would get it replaced. With long exposures you can
expect more, just make sure to turn on the in camera long exposure noise
reduction feature. This should help. I would also recommend something like
NeatImage to help with any other noise problems. http://www.neatimage.com,
great program.

John

Archived from groups: rec.photo.digital.slr-systems (More info?)

leo wrote:
> I got one white hot pixel. Should I bother to exchange it? How many
> people have got a perfect sensor? My last Digital Rebel (2nd one
> actually, the first one was exchanged for another reason and I didn't
> doa pixel test) had no dead/hot pixels. Thanx.

I thought there was a procedure in the 20D (most DSLR's) to map hot pixels such
that they be interpolated out in succeeding images?

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Archived from groups: rec.photo.digital.slr-systems (More info?)

Nope, not on the 20D and as far as I am concerned that type of feature is
only a excuse for the manufacturer to do less quality control, testing and
for not buying better quality sensors.

John

Archived from groups: rec.photo.digital.slr-systems (More info?)

On Sun, 19 Dec 2004 16:56:54 -0500, Alan Browne
<alan.browne@freelunchVideotron.ca> wrote:

>John Doe wrote:
>
>> Nope, not on the 20D and as far as I am concerned that type of feature is
>> only a excuse for the manufacturer to do less quality control, testing and
>> for not buying better quality sensors.
>
>It is likely that a 0 defect policy for over dead/stuck sensor pixels in over 8M
>would result in such a low yield as to make the product unafordable. I may be
>wrong, and I bet that Canon would be quite tight lipped about it in any case.
>
>I don't know if they have a 'dead pixel' spec for how many dead sensor pixels
>are acceptable at production. In fact, it would not surprise me at all that
>they do have a threshold and that they do detect dead pixels in the factory
>tests. In turn have them mapped in memory and use that to correct every image
>taken. If so, it's likely a very small number of dead sensors, like 10, such
>that it would never affect an image enough to be noticeable after the correction
>is applied.
>
>Given that these are spatially seperate R,G,B sensors, the loss of one of them
>won't affect the combined RGB pixel when it is computed, using data from the
>pixels around it in the interpolation.
>
> From there, recognizing that sensor sites might die a year or 5 or 10 years
>later, there should be the means to map and correct these as they occur. There
>is a procedure in some Nikons that actually "fixes" some dead sensors (getting
>them out of the 'stuck' state. If this applies to the CMOS sensors in Canon's,
>I don't know.)
>
>http://www.imaging-resource.com/NEWS/998087928.html is Olympus' response to the
>issue.
>
>(Hard disks with dead sectors come to mind... in the 10 MB disk days we would
>would moan over a single dead sector in a hard drive. The cost/bit was too
>high. Of course this didn't affect the quality of a document.)
>
>When film is returned it is not uncommon to have tiny scratches or bits of
>embedded dust in the emulsion. Not every frame, but 1 or 2 frames per roll.
>These are easilly corrected with ICE equipped scanners or a little handiwork in PS.
>
>Cheers,
>Alan

Some software offers a "dark frame" process to remove just the digital
pixel image from the main image. This is done especially for longer
exposures where more hot pixels might show up.
-Rich

Archived from groups: rec.photo.digital.slr-systems (More info?)

My 20D seems OK, zero hot pixels at ISO400 and 1/30 sec.

30 sec exposure there was one faint red spot - closer examination suggests
it is more than one pixel, also noise cancellation did not remove it. I had
the lens cap on, f32 set and shaded the eyepiece though I didn't use an
eyepiece cap.

Tentative conclusion was it was stray light - probably from the eyepeice. So
I am not worried.

I would be worried for a sub-second exposure though.

Cheers


Lester

"John Doe" <john_doe@nospam.com> wrote in message
news:Y60xd.13131$_3.146708@typhoon.sonic.net...
> At 1/60th of a second I would get it replaced. With long exposures you can
> expect more, just make sure to turn on the in camera long exposure noise
> reduction feature. This should help. I would also recommend something like
> NeatImage to help with any other noise problems. http://www.neatimage.com,
> great program.
>
> John
>
>