Removing red and green dots

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Hi

When taking pictures in low light my camera compensides by adding some red and green dots. Is it possible to remove these "wrong colored" pixels afterwards (by averaging the pixels or something like that)?

Yours cincerly, Lars

-- Lars Hejlemann (lhe@ddf.dk), March 29, 2000

Answers

Those red and green dots are CCD noise, not some sort of compensation.

There might be some software out there that could reduce the noise in the finished image by analysing an evenly dark area, doing a fourier transform or statistical probability analysis, and then overmasking with inverted noise, but I don't know of anything like that. If it does exist, it's going to be mega-expensive.

As a cheap alternative: Try dropping the black level with an image editor and expanding the tonal range to compensate. The darkest areas where noise is most noticeable don't contain any useful information in most cases anyway.

-- Pete Andrews (p.l.andrews@bham.ac.uk), March 29, 2000.


Idea number 2: If you've got Photoshop, separate the image into red, green and blue layers, and use the "dust and scratches" filter to clean up the red and green layers, then re-combine and flatten the layers.

-- Pete Andrews (p.l.andrews@bham.ac.uk), March 29, 2000.

If you own a PC then try Qimage. It does a great job in reducing all sorts of noise (bu not perfect) and is only $30.00 US. I own a Mac but liked the software so much I bought VirtualPC to run Windows on the Mac just to use Qimage.

http://www.charm.net/~mchaney/imaging/

Also take a look at agreat Photoshop plug-in that gets rid of coloured shadow noise in digital pics. It's called Quantum Mechanic. I love it and use it on nearly every shot from my Nikon 950. http://www.camerabits.com/QM.html

Cheers, Michael

-- Michael Liapakis (liapakim@ihug.com.au), April 12, 2000.


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