Re: [APML] Luminance with color film and deep-sky filter

[Jerry Lodriguss <jml@astropix.com>]

At 08:00 PM 4/4/2002 -0800, you wrote:
>At the moment I don't have much in terms of money and don't feel like
>dealing with TechPan to shoot a luminance shot. Instead I've decided to try
>just shooting it on the same roll as the color shot but using something like
>a deep-sky filter.  I doubt that I'd get better sharpness but I feel that I
>should be able to get much better contrast with nice color.  On an object
>like the Rosette I was thinking of shooting a 30-45 min shot unfiltered,
>then two 60-70 min filtered shots.  I would then convert the two filtered
>shots to grayscale, stack and curve them, then paste them into the color
>shot as a Luminance channel or layer.  I'm curious as to the possibility of
>good success and want to know if anybody has ever tried this technique.
>Also, any ideas on how to pull this off nicely?


I don't think you will gain anything from trying this.

The deep-sky filtered shots will present the best contrast already in 
color. The unfiltered shots will have less color than the filtered shots. 
So you'll be throwing away the best color in the filtered shots to make 
your luminance channel, and then you'll be combining that with your worst 
color in the unfiltered shots. That's not what you want to do.

The filtered shots will have the best luminance contrast, but they will 
also have the best color, so why throw it away.

You would get better results to just shoot four filtered shots and stack 
them all together.

Now, I have shot an h-alpha filter on E200 and substituted that in for the 
red channel in a color shot. That works very well for h-alpha objects.

Jerry
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