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Old Jun 29, 2004, 1:06 AM   #1
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I have an Oly C310. It has "Pixel Mapping" function in one of its menus.

Can someone explain what exactly this "pixel mapping" will do to my, or to any Oly camera?

I know about hot, stuck and dead pixels, I would like to know if this pixel mapping will fix them. And if so, how often should we perform this? Would it not degrade quality? Should care be taken when using this function?

I understand also that current ccds will develope hot, stuck and dead pixels over time.

I've read to some other brands that pixel mapping will block offending pixels on their shots. In our Oly, would it permanently block those pixels?

I tookshots in pitch black for 2 seconds in each shot (night mode) and then I noticed this faint dark pixel (gray color) in all of the shots and I would like to remove it. When opened in Photoeditor, the gray bit composes of 4 pixels...



Any comments?

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Old Jul 1, 2004, 1:59 PM   #2
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My manual suggests mapping once a year. It only works for completely dead or stuck pixels. It bypasses them as you suggest. It does nothing for the hot pixels you get when you do a long exposure with the lens covered.

http://www.imaging-resource.com/NEWS/998087928.html

http://www.olympus-pro.com/index.eu....elmapping.html
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Old Jul 1, 2004, 5:39 PM   #3
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The mapping function essentially detects stuck or dead pixels, ignores those pixels and substitutes via interpolation.

I wouldn't do it more than once, or perhaps twice, a year.

Mapping is irreversible.

There are some excellent noise reduction programs available, including some freeware ones. Try Helicon NoiseFilter.


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Old Jul 2, 2004, 2:59 AM   #4
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Thanks for the input.

While I as waiting for replies in this forum, I asked Olympus the same questions.
They did reply, though their's says that it could fix hot pixels too...

"Pixel mapping does fix hot, stuck and dead pixels. The right time to
use this function would be when you notice multiple hot, stuck, and dead
pixels that affect your pictures...," "...It is not necessary to operate this
function frequently. Approximately once a year is recommended. Wait a
few minutes after the monitor is used or continuous shots are taken to
allow for proper performance of the Pixel Mapping function," Olympus said.

If pixel mapping is irreversible, as you mentioned jkusmier, then Id probably would use it seldomly and not just to fix hot pixels coz I would want those pixels to work again on normal shots.

I wish Olympus would change their Pixel Mapping function to be smart, and if possible do it in real time. Effects would be reversble (resets the map then rechecks for pixel problems) Revives those hot pixels for normal shots and disables them when it detects the camera if it is in long exposure setting.

Thanks for the links. I am looking for a good noise/hot pixel remover software that does "lossless jpeg" saves.



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Old Jul 5, 2004, 2:26 PM   #5
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A true hot pixel will show up on a normal image. The kind that you induce with a long exposure won't and isn't removed by pixel mapping. Pixel mapping only bypasses pixels that would show in a normal photo, and you don't want those there. You will not lose any of the pixels that work fine normally but show up in a long exposure.

There isn't a "lossless JPG save". Anytime you save as JPG you get compression loss. It is almost impossible to see at Photoshop quality 12, but it isn't completely lossless. Lossless rotation rewrites the code in a different rotation without actually modifying and resaving the image. You can also rotate lossless by modifying the orientation in the EXIF. Anything that removes the hot pixels is going to change the image so it has to be re-saved. And that requires another JPG compression.
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Old Jul 6, 2004, 4:29 AM   #6
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Thanks for adding slipe.

I was able to find PixelZap, a hot pixel remover software that claims to save jpegs 'virtually lossless.' ( http://www.tawbaware.com/pixelzap.htm ) I tried it, and it worked almost perfectly. The automatic detection is ok, but I like the manual detection through the use of a pixel map file you can save on your harddisk. The shareware version would only allow me to save 640x480 images.

I also found Neat Image software to take care of the noise. ( http://www.neatimage.com ) 'Happy with the results. The demo version's functions are enough for me. Pixelzap for hotpixels, NeatImage for noise.

My new 'wish' list for Olympus Pixel Mapping
1. Separate pixel mapping, meaning separate pixel maps for dead/stuck pixels and hot pixels, including per ISO/shutter delay setting for hot pixels; making effective use of pixels when they could still do good.
2. Automatic switchingofpixel maps to be used when shooting pictures

"There's always room for improvement."



BTW, I found a r*g k*y for pz posted on one site. (I know what you're thinking... so blame it on the search engine...) DO NOT go to these kind of sites, doing so is 'asking for trouble,' unless of course you want to check how good your computer's security would stand-up.

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Old Jul 6, 2004, 10:57 AM   #7
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What my Oly needs is long exposure noise reduction. If there is a true hot, dead or stuck pixel I want the pixel mapping to bypass it. If I take a long night shot I would like the camera to compare it internally against a black shot of the same exposure and remove the noise artifacts. They vary with exposure and temperature and can't properly be removed with any kind of pixel mapping.

Steve has an extreme example of what it can do:
http://www.steves-digicams.com/2001_...tml#conclusion They dropped noise reduction on the C50. They made a lot of speed improvements on the C60 but didn't put the noise reduction back. I'm guessing it is a battery life problem. Otherwise it makes no sense. Most cameras in that price range and class have noise reduction. They also left the crappy 320 X 240 movies at 15fps. Again I'm guessing battery as the internal processing seems to be improved to the point where it could take 640 X 480 movies at 30fps. Shutter lag is about the best you can buy, cycle times are excellent and the camera will actually buffer 6Mp TIFF files, which is really unusual. To have 320 X 240 movies at 15fps with that level of performance is strange.
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Old Jul 6, 2004, 7:48 PM   #8
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The C60 does have dark frame noise reduction as does the C7xx seriesand other higher end Oly cams. Don't know why they dropped it in the C50 or offer it in the lower end P&S cams.

KuoH

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They dropped noise reduction on the C50. They made a lot of speed improvements on the C60 but didn't put the noise reduction back.
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Old Jul 6, 2004, 11:52 PM   #9
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KuoH wrote:
Quote:
The C60 does have dark frame noise reduction as does the C7xx seriesand other higher end Oly cams. Don't know why they dropped it in the C50 or offer it in the lower end P&S cams.



I don't doubt you are right, but it isn't anywhere in their specs on the Olympus site. Seems since they left it off the C50 they would be a little more aggressive about announcing they had put it back.
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Old Jul 8, 2004, 12:24 AM   #10
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That's normal for Olympus marketing it seems. When the C765 was first put on their site,they failed to mention the macro modes. It has since been corrected.

KuoH
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