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Old Jan 14, 2005, 1:01 AM   #1
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Hi, I have a Canon Powershot S1 (10x zoom) and lately when i take a photo i get a tiny blue haze on the image. See example pic below:

Click here to see photo

Ive circled the blue dot in white.

Please let me know what this could be, and if its a strong enought case to claim warranty etc.

Thanks for your help.

Cheers,
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Old Jan 14, 2005, 10:38 AM   #2
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Do you think its really a haze or just that dot? Take a picture of a white sheet of paper, that should show you how bad it is.

If its one pixel, there isn't much you can do. They keep the cost down by selling cameras even with a few bad pixels. I don't like it, but I'm not sure if its claimable for warrenty reasons. You can always try.

Eric
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Old Jan 14, 2005, 10:44 AM   #3
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If it shows up in the same place on every photo, then it's a stuck pixel (one that's always at a high value, regardless of exposure settings).

Here is a utility you can use to test for them:

http://www.starzen.com/imaging/deadpixeltest.htm

Note that hot pixels are normal for longer exposures. But, if they show up at faster shutter speeds (1/30 second or faster), then they are considered to be stuck.

If it bothers you, I'd send it back to Canon if it's still under warranty (making sure to include a sample image showing the problem). Most manufacturers have a utility that they run to map them out (updating an internal file kept by the camera, that it uses toreplace any pixels that are bad by using values from adjacent pixels).

If you can't send it back under warranty, and want to get rid of it in your photos, here is a utility that lets youuse a bad pixelfile to do the same thing by processing your images:

http://www.tawbaware.com/pixelzap.htm


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Old Jan 14, 2005, 6:51 PM   #4
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Thanks for your help guys, Just spoke to Canon and they are happy to repair it for me under Warranty.


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Old Jan 14, 2005, 10:14 PM   #5
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BTW, Nice Jeep!

Bring back the memories... 1986... last of the CJs...

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Old Jan 15, 2005, 3:27 PM   #6
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yeah... nice off-road shot...
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Old Jan 17, 2005, 10:16 AM   #7
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eric s wrote:
Quote:
Do you think its really a haze or just that dot? Take a picture of a white sheet of paper, that should show you how bad it is.

If its one pixel, there isn't much you can do. They keep the cost down by selling cameras even with a few bad pixels. I don't like it, but I'm not sure if its claimable for warrenty reasons. You can always try.

Eric
That's pretty disgusting how they sell their cameras even when the pixels are bad.
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Old Jan 17, 2005, 10:38 AM   #8
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You see complaints about bad pixels from all of the manufacturers from time to time anymore.Part of it is probably that sensors are becoming very dense.

But, virtually all cameras have an internal table that tracks bad pixels and maps around them.Even with older models, I can remember users sendingback cameras for "CCD Repair", and figuring out that the same CCD was still in the camera when they got it back.

They determined this by looking at hot pixels on longer exposures, and shooting with the repaired camera later. The hot pixels were in the same places (even though "stuck" pixels visible on normal exposures were no longer visible).

I suspect that virtually ALL CCD's on consumer digicams have a number of bad pixels. We just don't see them because the factory maps them out ahead of time (with the camera interpolating values from adjacent pixels to replace the ones that are bad). But, sometimes they can develop bad pixels later. So, some if it may be QC, and some of it may be bad luck. ;-)

When you think about it, the pixels you see are all interpolated from surrrounding pixels anyway. That's how a digital camera works (with the exception of the Foveon sensors). You've got a color filter array, with each pixel only sensitive to one color (with the sensors actually being color blind -- the filters simply block out all colors except for one for each photosite). Then, the image processing algorithms combine the values from multiple photosites into individual pixels when processing the images.

That's why a 3MP Foveon sensor can produce as much detail as a 6MP or higher Bayer Type Sensor.

Are you really going to see an impact from a couple of bad pixels out of millions, when the values are being interpolated from surrounding pixels to replace them after the factory maps them out? I don't think so.

A lot of newer models map them out automatically now, too. Olympus started this trend with their E10 model (whichrequired a firmware upgrade to get this feature). Now, you're seeing the same type ofpixel remapping functions built intoa number of modelsfrom Konica-Minolta and Olympus.Canon has beena little slow "jumping on the bandwagon", but I think they'll probably put this feature into future models at some point, too.



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Old Jan 17, 2005, 9:22 PM   #9
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JimC wrote:
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...
A lot of newer models map them out automatically now, too. Olympus started this trend with their E10 model (which required a firmware upgrade to get this feature). Now, you're seeing the same type of pixel remapping functions built into a number of models from Konica-Minolta and Olympus.
Interesting - sensible solution for minor problems. Does it slow down the write speed noticably? How are they dealing with stuck/hot pixels in the RAW output?
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Old Jan 17, 2005, 10:32 PM   #10
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Bill:

I don't know about the write speed. Since this feature can't be disabled (the image processing part, where the camera uses the bad pixel table), there's no way to tell for sure.The evidence I've seen reported suggests that it's been incamera models for a long time, and we just didn't know about it.

Newer Olympus modelshave a menu choice (Pixel Remap). It identifiesany bad pixels and apparently updates an internal tablethat the camera knows about when processing images.

Older Nikon and Olympus models also have a bad pixel table (but no user available menu choice to update it). But, a Russian Programmer figured out how to get it to and has a downloadable utility that seems to work on some of these models (some Nikon and Olympus models apparently shared a common chipset and interface language). I've seen users of various Nikon and Olympus models report that it works on them -- including models like theOlympus 2100UZ, 3030z and Nikon 990:

http://e2500.narod.ru/ccd_defect_e.htm

KM is apparently doing it automatically once a month now on their newer models (i.e., A2, A200). A user was advised by KM in the U.K. to set the date up one month, turn on thecamera, turnit back off again, and set the date backcorrectly. Thestuck pixels were then gone. I've seen multiple users report successusing this technique.

As for RAW, I don't know how it would handle it.... I have not seen anyone report if the stuck pixels were still in the RAW File. I guess it's possible that the bad pixels are being replacedwith values from other pixels prior to the RAW file being written out to the media.

If not, then these users would need to handle it via Post Processing. David Coffin's dcraw.c supports a bad pixel file that he uses when performing RAW conversions. It's setup so that you have both pixel coordinates, and the date the pixel went bad. He looks at the date the image was taken when performing a conversion from RAW. That way, he doesn't replace pixels in older images that you may want to reconvert from RAW (since the bad pixels may not have occured until later in a camera's lifespan).

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