RE: [APML] Noise Reduction was (Image Processing Question:GaussianBlur vs Unsharp Masking)

["Jay E. Potts" <jpotts@americanfocus.com>]

Rob, I agree that if you can tell grain reduction or noise reduction has been
done, than it has been to much or poorly.

However, unlike CCD, film always has grain visible even with lots of signal and
I have noticed different tools specifically designed for film grain reduction
can produce slightly different results.

~ Jay E. Potts
http://www.whirlpoolgalaxy.com (Astrophotography)
http://www.americanfocus.com (Landscapes & Wildlife)




-----Original Message-----
From: astro-photo-bounces@seds.org [mailto:astro-photo-bounces@seds.org] On
Behalf Of Robert Gendler
Sent: Friday, November 05, 2004 1:02 PM
To: Discussion of Film Astrophotography
Subject: Re: [APML] Noise Reduction was (Image Processing Question: GaussianBlur
vs Unsharp Masking)

Noise reduction really has little to do with the type of technique/program
used.
Whats much more important is getting the reduction in the parts of the image
that
need it. IMO there's nothing more unattractive than an image that looks like
wax
from excessive, and nonselective noise reduction. I'd rather see an image
with
a little grain/noise than see something that looks overly smoothed and
artificial.
I have found that most of the programs work in a similar manner including
gaussian
blur, Grain surgery, etc. The key is selecting low S/N areas. I do this with
the use
of the color range tool in PS. Use the dropper to select the areas with the
most
noise (you can even select regions within a single color channel). Titrate
the degree
of the selection with the slider and then apply the reduction of your choice
(blur,
median, dust and sctratches grain surgery, etc.) .

ob Gendler
email: robgendler@att.net
Web Site: http://www.robgendlerastropics.com
----- Original Message ----- 
From: "Vicent Peris" <vicent@cepheusastrophoto.com>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Friday, November 05, 2004 3:17 PM
Subject: RE: [APML] Image Processing Question: Gaussian Blur vs Unsharp
Masking


> Hi Jay,
>
> you must try the new version of SGBNR, you will not loss faint details.
> Also, the best way to perform SGBNR is through a mask.
>
> Regards,
> Vicent.
>
>
>
> At 11:26 05/11/2004 -0800, you wrote:
> >Hello Charles,
> >
> >I have had pretty good luck with Grain Surgery. It is somewhat expensive,
> >but is a little easier to use than other grain reduction applications.
> >There are some situations where artifacts can be introduced, but most of
> >the time it does a very good job at retaining the low contrast detail and
> >sharpness while significantly reducing grain. One intangible benefit of
> >using Grain Surgery is that since it is a plug-in for Photoshop, you can
> >use it with the other features of Photoshop - Including performing grain
> >reduction on selected parts of the image using the magic wand tool etc.
> >
> >I did a comparison of various products and techniques a while ago:
>
><http://www.whirlpoolgalaxy.com/grain_removal.html>http://www.whirlpoolgala
> >xy.com/grain_removal.html
> >
> >To be fair, I have not updated this page with a comparison to the latest
> >release of SGBNR in PixInsight LE. SGBNR is very good, but it seems to
> >blur the image a little more than Grain Surgery. It has the advantage
> >however, of not introducing artifacts.
> >
> >Just my .02
> >
> >~ Jay E. Potts
> ><blocked::http://www.whirlpoolgalaxy.com/>http://www.whirlpoolgalaxy.com
> >(Astrophotography)
> ><blocked::http://www.americanfocus.com/>http://www.americanfocus.com
> >(Landscapes & Wildlife)
> >
> >
> >
> >
> >----------
> >From: astro-photo-bounces@seds.org [mailto:astro-photo-bounces@seds.org]
> >On Behalf Of Charles Shahar
> >Sent: Friday, November 05, 2004 6:37 AM
> >To: astro-photo@seds.org
> >Subject: [APML] Image Processing Question: Gaussian Blur vs Unsharp
Masking
> >
> >Hi Everyone:
> >
> >I have an image processing question: I am getting quite adept at pulling
> >out faint nebulosity using the curves and levels tools in Photoshop. The
> >problem, of course, is that these faint wisps of nebulosity often have a
> >"grainy" appearance to them. Since I intend to print these images, and
not
> >wanting to over-emphasize the grain, I am often caught in a quandary over
> >just how far to go when pulling out these faint details.
> >
> >So I am using the Gaussian Blur tool to mask the grain a bit. More
> >specifically, I am using the Adaptive Filter function in Iris, an image
> >processing program. This tool has a similar effect, in that it blurs the
> >object and masks the grain. But now I am bothered by slightly blurry
> >images. So I have tried to use unsharp masking to compensate. But this
> >solution is only half-successful, because the image starts to get grainy
> >again.
> >
> >Does anyone have any solutions for this problem, or should I just settle
> >for the best balance between grain and blur? Thanks for your insights,
> >
> >-Charles
> >_______________________________________________
> >Astro-Photo mailing list
> >Astro-Photo@seds.org
> >http://seds.org/mailman/listinfo/astro-photo
>
> Vicent Peris
> http://www.cepheusastrophoto.com/Index.html
> http://www.pleiades-astrophoto.com/pixinsight
>

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