Re: [APML] Bill Fletcher's Tri-color work(was 23a filter)

[Michael Stecker <mstecker@earthlink.net>]

Ulrich Beinert wrote:

> > Hello Scott:
> >       We all owe a lot to Bill Fletcher.  He was a pioneer in
> > film-digital astrophotography (not just tricolor).   I believe he
> > perfected his process in 1992 or perhaps 1993, which was years before
> > anyone on this list was doing such work.  He did this with Photoshop 2.5
> > (no layers) which made it vastly more difficult than it is today.  He
> > spoke to Adobe and they thought his process at the time was impossible.
> > Even with this discouragement he was able to develop a process that works
> > quite well.  In the November, 1994 Sky and Telescope on page 98 he wrote
> > an article on his technique.  The article was general and gave little
> > specific data.  The lead photo of the article was a tricolor of
> > Antares-Rho Ophiuchus region which I took with my Tamron 180 mm f/2.5
> > lens and hypered Tech Pan film and Bill processed in Photoshop 2.5.  It
> > has been a long time since I took that photo (I think it was in 1993).  I
> > believe I used a Kodak 25A for the red, 58 for the green and 47 for the
> > blue.  The exposure times were 42 minutes in red, 80 minutes in green and
> > 100 minutes in blue.  In later work I increased the green and the blue
> > exposures.  In my experience the hypered Tech Pan is least sensitive to
> > green light.  The most challenging tricolor I have done was of the very
> > dim SNR Simeis-147.
>
> If I understand this right, you take one photo through a red filter, one
> through green, and another through blue? Then what - stack them in Photoshop
> assigning them to the red, green and blue channels, respectively, to get a
> color image? This sounds interesting; I want to try it....
>
> Ulrich
>
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Hello Ulrich:
     You are correct !  That is exactly how we make our tricolor images.
Actually, the first color photos ever made were tricolor images by the 19th
century physicist James C. Maxwell who did it years before color film was
invented.

                                                Michael Stecker


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