Re: how to estimate the additive noise and get rid of additive noise in image?

From: Pat (a_at_b.c)
Date: 11/09/04 

Date: Mon, 08 Nov 2004 21:36:51 -0700

kiki wrote:
> Hi all,
>
> I obtained some pictures using camera. It looks to me there are some
> additive noise that was added to all image pixel components: from what I've
> observed, there are many small fluctuations/peaks/spikes of height 10-30,
> while the useful image region has values about 300.
>
> I am afraid that such noise has also been added to the useful image region,
> so the images have been universally shifted by 10-30 noise values. How can I
> estimate the noise and substract the noise value from those useful image
> region? Can I take the average of 10 and 30 and get 20, and then substract
> the 20 from all images?
>
> Any better ideas?
>
> thanks a lot
>
>

Hi,

If you are certain that it is unwanted additive noise, then take all
values that fall in that range and substitute the 'true' value. I saw
that one many years ago on some pictures of saturn and the results were
stunning.

They called it something like a stairstep function. The output for some
range of values is a single value.

If you encounter a soft gradient type of image, all bets are off.

Pat

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