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NoiseReduction

Image Noise Reduction


I asked the CGE Uncensored group(external link) what they felt about noise reduction software:

I have seen posts here and in the CCDNewAstro(external link) group that refer to
three packages: Neatimage, ))NoiseNinja, and?PixInsight((. The first two
will work both as plug-ins to Photoshop and standalone. ))PixInsight(( is
standalone. Both Neatimage and ))NoiseNinja(( cost $75-$80 for the full
version which is what you need for 16bit images. ))PixiInsight(( has a
freeware version.

Update 29-Apr-07

In discussion in the Astrophography section(external link) of the Bad Astronomy / Universe Today Forum(external link), the product Noiseware(external link) was mentioned. It has a freeware version and the pro version (required for 16 bit) is $69.95.

Here are the responses.

Samir Harusi(external link)


I think it all depends on how automated a process you want it to be.
An automated process makes sense for daytime photography, simply
because of the numbers of images one wishes to treat, less so for an
astro image that you have spent hours working on and are very
willing to spend another 10 minutes on the noise. Basically all
these programs do the same thing: determine some cut-off in
brightness and Gaussian blur everything below that brightness level.
Very easy to do manually and very precisely in most image editors.
Blur radius and strength of blur (or opacity of blurred layer) are
the other main controls. There is another noise limiter I use
routinely but does not seem very popular. Add a smooth, noise-free,
colored layer for your background sky. I like my background sky to
be 10% Blue, 5% Green and Zero Red. No logic. I just like my
background sky that color. Most people prefer grey (say
RGB=10%,10%,10%), for their own, equally illogical reasons, since
the night sky is a toffee/chocolaty color ;-) Anyway use
the "Lighten" blend mode and presto, super smooth, nil noise
background! Or back off a bit to show some noise. Mind you, easy to
overdo. See the background to the M88 1:1 crop inset in this image
(yes, a bit overdone but it does illustrate the technique well):
http://www.pbase.com/samirkharusi/image/55419099/original(external link)


Bud Guinn(external link)


I've had Neat Image for years..and it works well, but you must be very
careful to not lose data.

Probably the best that I've ever seen is Noel Carbonis' Astro actions.

http://actions.home.att.net/Astronomy_Tools.html(external link)

His ))DeepSpace(( Noise Reduction is, without a doubt, the very best I've
seen for a noise reduction without harming the nebula/galaxie areas.

If you want a heavier noise reduction then his Space Noise is very
good....I use it with layers, however,...it will attack some of the
nebula areas if you're not careful.

Lyndon Thompson(external link)


Personally I find that some technique is essential. Obviously more imaging
time leads to less noise but does not eliminate it.

Have you tried using layer masks to mask the important data and then
blurring the background? That is the technique I used in this uninspiring
image here today, http://www.lyndonthompson.co.uk/filevault/m103-LRGB.jpg(external link)
however the background is reasonably OK.

Mike Dodd(external link)


I use NeatImage(external link) in Photoshop CS2.

After an initial heavy-handed approach, I now take pains to keep the
noise reduction to the bare minimum. My process normally is to start
with several iterations of levels and curves, per Ron Wodaski's new Zone
System book. This brings up the background level.

When I begin to see the background noise, I flatten the image (the
levels and curves are done in adjustment layers, but ))NeatImage(( doesn't
seem to want to work in an adjustment layer). With the image flattened,
I make a copy of the background layer and apply a very slight ))NeatImage((
- just enough to smooth the visible noise slightly. There's still some
grain, but it's less obvious. Then I switch the ))NeatImage(( layer on and
off to blink the before and after versions. I also check to be sure I
haven't inadvertently "buttered-over" some nebulosity. If so, I'll
delete the ))NeatImage(( layer and try again - or abandon it entirely.

Once ))NeatImage(( is applied, I do another levels and curves iteration to
fix up any changes it made.

Created by Andy. Last Modification: Sunday 31 of October, 2010 17:06:18 CDT by Andy. (Version 1)