Re: [APML]: Scanner Bit Depth

[Jerry Lodriguss <jml@astropix.com>]

The Astro-Photography Mailing List
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>I've never had any astro images scanned onto PhotoCD, but my experience with
>daylight PhotoCD has been that the quality can vary considerably from place
>to place (probably operator to operator). I would be surprised if that were
>not true for astro images as well. So, it might be difficult to come to any
>conclusions about how PhotoCD compares to scanner X if you only use a
>PhotoCD from one place.


When you open the PCD images in Photoshop, you will notice a bunch of
different ways you can do this.  Make sure you match the source with the
way your image was scanned (I don't know if it indicates whether SBA was on
or off anywhere). 

Then experiment with opening the same image up into different color spaces.
 In PS 4.01 I found 16 different permutations here (between source film
terms and target color spaces), and each looked different.

Try each, and compare each to the original viewed on a 5,000K light table
next to your monitor. Try blocking out all of the extra light from the
light box with a cardboard mask with a 1 x 1.5 inch rectangle cut out for
the slide.  If you shot color negs as originals, never mind.<G>

Jerry
mailto:jml@astropix.com
Web page: http://www.astrosurf.com/astropix/index.html 
Astrophotography,Photoshop enhancement tips and techniques