Dead Pixels in *ist DS CCD Sensor?

I see at least 4-5 of them. A few tiny red, green dots in exactly the same spot in every pic I take.

Is this considered "normal" like the way LCD manufacturers like to weasel their way out of poor quality control?

-Ed

Edwood said:

I see at least 4-5 of them. A few tiny red, green dots in exactly
the same spot in every pic I take.

Is this considered "normal" like the way LCD manufacturers like to
weasel their way out of poor quality control?

-Ed

Click to expand...

I was told by Pentax UK that if I got any dead pixels they would do something about it as long as it was under guarantee. So it's up to you whether you want to send it in. I'm assuming that wherever you live the Pentax policy is the same. I haven't noticed any on mine yet, I would hope that that number is abnormal.

John Mc Dermott said:

I was told by Pentax UK that if I got any dead pixels they would do
something about it as long as it was under guarantee. So it's up to
you whether you want to send it in. I'm assuming that wherever you
live the Pentax policy is the same. I haven't noticed any on mine
yet, I would hope that that number is abnormal.

Click to expand...

I can confirm that the same policy is valid (at least in theory) here in Bulgaria: if you have even only one dead pixel on the sensor, you'll get your camera either repaired or replaced.

Edwood said:

I see at least 4-5 of them. A few tiny red, green dots in exactly
the same spot in every pic I take.

Is this considered "normal" like the way LCD manufacturers like to
weasel their way out of poor quality control?

Click to expand...

No, these aren’t dead pixels (dead pixels are always black), but stuck pixels (always the same primary colour). And no, this is not considered normal. The sensor may have a few dead or stuck pixels, but the firmware should know about these and ignore them.

• Michael

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http://www.michael-hussmann.de

You're right, but the hot pixels can appear with time and the camera software (I think there is a hot pixel map that 'tells' the camera what to ignore) does not know about them. The pixels can be remapped by service, so you should send the camera in while still under warranty.

Here are some useful resources:

http://webpages.charter.net/bbiggers/DCExperiments/html/hot_pixels.html
http://www.starzen.com/imaging/deadpixeltest.htm

Michael J. Hußmann said:

Edwood said:

I see at least 4-5 of them. A few tiny red, green dots in exactly
the same spot in every pic I take.

Is this considered "normal" like the way LCD manufacturers like to
weasel their way out of poor quality control?

Click to expand...

No, these aren’t dead pixels (dead pixels are always black), but
stuck pixels (always the same primary colour). And no, this is not
considered normal. The sensor may have a few dead or stuck pixels,
but the firmware should know about these and ignore them.

• Michael

--
-------------------------------------------------------------
http://www.michael-hussmann.de

Click to expand...

Ah, so they're Hot Pixels!

I took a few test shots with the lens cap on.
The only time I could see the hot pixels was in night photography.

I could only see the hot pixels with the following settings.
Exposure 1/8sec
F 1.4
ISO 3200
Focal Length 50mm

They are barely noticeable at ISO1600.

I even shot at ISO3200 with a 20sec exposure time, and the hot pixels were not as noticeable because the noise level was more uniform.

Thanks for the info. I feel much better now.

-Ed

tomaszmatys said:

Here are some useful resources:

http://webpages.charter.net/bbiggers/DCExperiments/html/hot_pixels.html
http://www.starzen.com/imaging/deadpixeltest.htm

Michael J. Hußmann said:

Edwood said:

I see at least 4-5 of them. A few tiny red, green dots in exactly
the same spot in every pic I take.

Is this considered "normal" like the way LCD manufacturers like to
weasel their way out of poor quality control?

Click to expand...

No, these aren’t dead pixels (dead pixels are always black), but
stuck pixels (always the same primary colour). And no, this is not
considered normal. The sensor may have a few dead or stuck pixels,
but the firmware should know about these and ignore them.

• Michael

--
-------------------------------------------------------------
http://www.michael-hussmann.de

Click to expand...

Click to expand...

Edwood said:

Ah, so they're Hot Pixels!

Click to expand...

Hot pixels look like stuck pixels (which is what you’ve got), only they aren’t really "stuck". Hot pixels accumulate with long exposure times (typically 1/2 sec and more) if noise reduction is turned off. They don’t show up in normal exposures. Stuck pixels, on the other hand, are always "on", regardless of the exposure time. Also, there are typically just a few stuck pixels (if at all, as there should be none), while the hot pixel count can easily reach 1000 and more, if the the exposure time is long enough.

• Michael

--
-------------------------------------------------------------
http://www.michael-hussmann.de