RE: [APML] Image Processing Question: Gaussian Blur vs Unsharp Masking

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

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
http://www.whirlpoolgalaxy.com (Astrophotography)
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