Re: [APML] Grain Reduction?

[astropix@att.net]

 Hey Alen...

     I'm certainly *not* an authority by any stretch, but if you're willing to 
listen, I'll be happy to share my very limited experience here. I had good 
results on single exposure noise reduction on this particular image by making a 
blur with Photoshop Median filter and compositing the blurred image with the 
sharp one in Picture Window Pro... see ------------------------------------->

                 http://home.att.net/~astropix/M42_135mm.html

... the Median filter was set at 100%... the Composite slider was set at 66% in 
Lighten mode. I'm not sure this will work across the board... probably best on 
images with lots of faint stuff. (I need to edit my text to more accurately 
explain processing involved)

     I've also used SGBNR on a handful of images... this one in particular 
comes to mind... see -------------------------------------------------------->

                 http://home.att.net/~astropix/Earthshine.html

... this shot was a little under exposed, and I had to stretch it a bunch to 
make anything of it. This brought out the noise - big time. SGBNR made it 
somewhat presentable. I'm sure SGBNR could do even more with an experienced 
processor working the controls. For me, the trick seems to be learning 
to 'read' the masks for each color channel: Black areas of the mask change 
nothing - White areas change everything. Learning how the controls effect the 
mask layers takes some practice... it probably helps if you can relate to how 
the algorithms function... I'm still scratching my head there.

     This may be wrong, but I do unsharp mask as the very last thing... noise 
reduction next to last. In fact, after the Median/Composite function on the 
Orion shot, I was able to boost the Saturation a little more in the composite 
image from previous levels... I guess the end result matters most, but I think 
you should definitely do all Curves before any noise reduction efforts.

 Hope This Helps...

 Geoff Powers

--
http://home.att.net/~astropix/


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