Re: [APML] TSP wide field images and film grain question

["Carlos Milovic F." <cmilovic@yahoo.es>]

>I finally had a chance to process some film shots from this year's Texas
>Star Party and I wanted to share them and hopefully get some tips on
>processing dark nebula to remove noise. One image in particular (Pipe
>Nebula - high res version) has some dark green pixels spread >throughout the
>dark regions that I assume are some kind of film grain artifacts???

 

The green "hot" pixels usually are generated in the scanning process. They are electronic noise, not grain artifacs.

 

>Anyone
>know what causes this and how to best process it out?

Becouse the green channel ussually don't have usefull information, you can try some radical ways to eliminate them. One of the best process is the called SCNR (Substractive Channel Noise Reduction). You can read about it in Juan Conejero's homepage: www.pleiades-astrophoto.com

Also you can try Juan's software, SGBNR (Selective Gaussian Blur Noise Reduction), that works very well to reduce the noise due the film's grain.

 

 

Regards,

Carlos Milovic F.
-------------------------
Astro & Photo - CMF
http://www.astrophoto.vze.com
-------------------------
Visita "AstroFoto", el foro de astrofotografía en español
http://espanol.groups.yahoo.com/group/astrofoto

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