Re: [APML]: Color Film and Filters

[Steve Bell <sb635@delphi.com>]

Chuck Vaughn wrote:
> 
> Jack Schmidling wrote:
> >
> > The original objection I had was making stars that are not red, red and
> > I guess we agree that this in not legit because stars are stars.  If
> > a filter does this, to a color photograph, it presents an untrue
> > image even if it brings out other reds that really are there but can
> > not be seen.
> 
> The main idea of the DS filter is to allow more nebula to be recorded.
> You just have to ignore the fact that star colors will be altered and
> enjoy the nebula. :-)
> 

I've been laid-low with a back problem for the last couple of days, and I've just now 
gotten a chance to read all the "Color Film and Filters" thread, and I have a few 
comments.

The only color photos I've seen through a DS filter are the ones by Jack Marling in 
AMOACP and the ones recently presented by Jerry Lodriguss on his hoempage. If you look 
at Jack's, you'll notice that they are all of red-colored emission nebulae. He also 
presents a couple of galaxy photos, but he took these *without* filtration. Since 
galaxies are generally more blue than anything, I don't know if he'd agree, but from 
that I'd suppose Jack Marling views the DS filter as basically a red filter, best used 
on emission nebulae.

Also, I think its reasonable to judge the predominate color transmission of a filter 
by holding it about a foot from your eye in a room well lit using your standard GE 
frosted light bulbs (which (I think) irradiate in all colors, ie, give off white 
light). When I do this with my DS, it looks purplish-red to me, strengthening my 
opinion that for photography (be it B&W or color), it's best used on emmission 
nebulae, where you want to record essentially nothing but red. But then again, there's 
Jerry's photo of the Veil, and I'm amazed (and perplexed) at how he got anything 
yellow recorded through a DS, since in that region of the spectrum, its transmission 
is zipola.

-- 
Clear skies,
Steve Bell
sb635@delphi.com
http://people.delphi.com/sb635 - Astrophoto page