Hot pixel mapping for the C-2100 UZ works!

Started Sep 5, 2003 | Discussions thread
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corhoin OP New Member • Posts: 16
Re: Worse results after remapping?

Inigo Montoya wrote:

Unless you got your image labels backwards, I see a lot more
noise/hot pixels in the "after" shots taken at 16 seconds for both
ISO 100 and 400.
The 4 second exposures do seem improved, and I guess it's worth the
trade off at the extra-long end of the exposure range unless you're
into 16 second night/astro shots?

The 16-second results depend very much on the temperature of the camera. If the camera has been on for some time, the CCD and other electronic parts are very warm. Now there's much more noise in long exposures than right after turning the camera on after a half-hour break. It's called thermal noise, and can't be avoided by mapping out the noisy pixels, as they are all more or less noisy. The only way to avoid this is to cool the CCD somehow, e.g. with a peltier cooler like in real astro applications.

It looks to me that the erratic pixels are gone in these pics, and there's only noise left.

If you really want to take low-noise 16-second pictures with an UZI, the final noise could be easily reduced by taking a dark calibration shot with the lens cover on just after every "real pic" - just like the noise reduction function in new cameras. After this you could use the Mediachance BlackFrame NR software to eliminate most of the noise. It can also be used to reduce the effect of real "hot" or "stuck" pixels, but the sharpening and JPEG compression won't make your job easier at all - that's why it's better to eliminate the faulty pixels or pixel groups before any further image processing.

Cheers,

Vesa
--
Corhoin Wizardonik Customworks, Finland

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