Re: [APML] LRGB - film only

["John C. Mirtle" <spampit@shaw.ca>]

Keith,
    Try it with just one TP and one or two colour images. You will probably
just need one colour neg for the bright stuff. I have done a bit of this,
the grain from the colour image doesn't really degrade the TP image much at
all. You will get a much sharper image than shooting colour alone. At f7
under good skies you can go much longer with tech pan. I have a couple of 2
hour shots for you to look at, one using a Deep Sky filter:

http://members.shaw.ca/jmirtle/pickering.htm
http://members.shaw.ca/jmirtle/m33.htm
http://members.shaw.ca/jmirtle/m33-crop.htm

    Tech pan just keeps going, there is way more stuff in the 2 hour shots
than with their 1 hour siblings. If you try 2 hours under poor skies, you
will just get material for a solar filter... The tricky part to L/C
composites (luminance and chroma, it's not true RGB) is getting the contrast
of the tech pan somewhere near that of the colour image. If the contrast of
the tech pan is too high - and it almost always is - you will get really
goofy colours when you throw the stack together. Fortunately, Photoshop has
a contrast control. Check out Bobby Middleton's web site, he has done lots
of this. http://www.koyote.com/users/bobm/astro1.htm

Good luck, and welcome to the voodoo world of film......

John Mirtle
Calgary, Ab. Canada

----- Original Message ----- 
From: <kasism@comcast.net>
To: <astro-photo@seds.org>
Sent: Tuesday, October 07, 2003 2:01 PM
Subject: [APML] LRGB - film only


Hello,

Having done ccd color work and seeing LRGB using ccd (L) and film (rgb), I
have laid out a project for some color imaging with a 140mm APO on 35mm film
and have decided to go LRGB by shooting Hypered TP followed by hypered
RG200.

Following my experience with CCD work, normally I would shoot L at high
resolution for 2 to 5x the RGB (RGB is just for color, L is for details)
shot at lower resolution.  However, I am wondering if due to the sensitivity
of film vs ccd if this relationship is applicable.  Currently I am planning
to shoot 2 TP @ f/7 for 1 hr each, 1 TP @ f/7 for 20', 2 RG200 @ 1 hr each.
Ok, so that is almost 5 hrs per image.

Has anyone done this kind of lrgb?  Is it necessary to shoot so long on rgb
or should that be reduced by ?half? just to colorize the TP image?   Would
the RG200 image degrade (due to color layers) the TP image to the point that
I may as well just shoot color only?  I really think that the RG200 will
give less definition than the TP image and it may not be 'blendable' without
serious impacts to the TP images.

Any views appreciated.

Keith

--
http://home.comcast.net/~kasism
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