Are bigger pixels less noisy?

Started 5 months ago | Discussions thread
JahnG
OP JahnG Veteran Member • Posts: 3,341
Re: Noise reduction

alanr0 wrote:

JahnG wrote:

Alan, interesting issues concerning noise reduction.

My original pixel-size and noise questions have been thoroughly and very well answered, so yes, why not slightly look at noise reduction, which probably is quite interesting for many.

Not something I know a great deal about.

I did get some satisfying results using Neat Image, but that was 10 years ago, and things have moved on since then.

Have you checked out the DPR Retouching Forum. There are some active threads on noise reduction there, including some specifically about Topaz Denoise which J A C S mentioned.

I shoot jpg and very seldom use NR in my old PaintShop Pro 9 program, which mainly seems to just blur the picture when using NR. Only when there has been some easily defined ("lassoed") noisy area on a picture I have "blurred" that area. I do own a "newer" PaintShop Pro program, the X5 version, which I have seldom used as the old version "9" works perfectly well in Win10 pro and is slightly simpler and faster to use. Both programs basically seems to do the same thing.

I just checked (in the net) that my newer X5 version has an additional NR setting, "digital noise" where different colored areas might be "noise reduced". Must look at it, but I doubt it is very advanced?

However, it seems that some more advanced noise reduction plugins would be possible to utilize not only in Photoshop but also in PaintShop Pro X5. (I'm Shooting jpg)

I found a program in Amazon.de (which I use, being in EU) named AKVIS Noise Buster, but it is probably not anything advanced at all? Any other suggestions?

What are BTW "non linear" noise reduction systems, some plugins?

One particularly simple noise reduction scheme is a linear low-pass filter. This attenuates high spatial frequencies. Essentially it averages out the noise, which it assumes is random. Unfortunately, this also smears out wanted detail in the image. A variation on this is to smooth out low amplitude noise below some threshold. Larger changes are assumed to correspond to actual wanted detail, and are passed through mostly unaltered. This is one version of a non-linear process, and thresholding is a common option in image processing packages.

Another non-linear technique is median filtering. Instead of finding the average intensity in a 5 or 9 pixel square, one sorts the nearest neighbour pixels in order of size, and replaces the central pixel with the intensity from the middle of the list (the median value). This is an effective way to remove the "hot pixels" that J A C S and Eric Fossum discussed, but in its simplest form it too can lose al lot of wanted detail.

The most effective noise reduction algorithms have more sophisticated means to figure out which parts of the image are actual detail and what is noise. I am not up to speed on the latest developments here.

If you don't get a detailed answer in this thread, you could try asking a new question specifically about noise reduction. Some of the local signal processing experts could be avoiding this thread, as pixel size has been argued over repeatedly in the past.

In addition, you should find well informed voices in the the Retouching form, particularly on the subjective merits of different products.

Good luck!

Thanks, will try

Jahn

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