RE: [APML] SprintScan 120

["Jon Kolb" <jkolb@datawest.net>]

Jason,

> I think I am getting the best results using Vuescan
> and dumping out a raw file. Then taking that file
> and setting the black/white points in Picture Window.
> 
> Anybody else using this technique? Tips and tricks?

Welcome back.

I'm using the SS120 and scanning "raw" 16-bits/color, but I'm just using
the Polacolor software to do it.  Since raw scanning applies no
corrections, I'd be interested to know how Vuescan helps you out here.

In addition, I use PW exclusively for image enhancement (with some
Registar for stacking, but no PS).  I'm finding that I have the best
luck by separating the R, G, and B channels and using the Brightness
Curve to get the background where I want it, as well as enhance the
faint stuff.  Final tweaks, smoothing, or whatever else are done after
combining the channels back together.  

I've also been playing around with brightness masks, well feathered, to
save some sharpness in star fields when using the Gaussian Blur function
to smooth grain.  The G channel makes a good brightness mask for stars,
since it usually contains little if any bright nebulosity, and thus a
mask made from it can pick up all the tiny stars without also including
nebulous areas.

Another trick that Tony Hallas calls the Green Ray Gun technique in PS
can be used in PW as well. It involves zooming way, way in until you can
see individual pixels clearly.  Then, with a 1-pixel probe in the
Color/Correction tool, I select really hot green or blue-green (or
whatever offending color I happen to have) pixels and slide them to a
more neutral color.  This has successfully reduced green-blue casts in
the dense star fields of wide-field shots without impacting other
features of the image.  I've also used this technique to shift E200's
orangy Ha nebulosity more toward the intersection of the blue and red
sides of the color cube. Altering nebula colors with this technique
requires moderation and restraint, and only requires one or two pixels.

Sean Walker's, and Matt BenDaniel's individual anti-vignetting
techniques can also be done in PW after a fashion, but they're so much
work that I've settled on cropping when needed.

Chris Cook had an interesting technique for using the B channel as a
filter (or was it subtractive filter?) in the Composite tool to enhance
his Witch's Head image, but I've forgotten the details.  Perhaps if
Chris reads this he'll refresh us.

I'd be interested to hear if any of this stuff works for you, and any
ways you find to expand on them.

Sincerely,
Jon Kolb
Adventures in Astrophotography
http://home.datawest.net/jkolb/
jkolb@datawest.net




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