Re: [APML] Im Blue

["Rick Krejci" <rick.krejci@psware.com>]

Just a guess...It may be a scanner calibration problem.  I looked at the
levels in Photoshop and after adjusting each curve such that the red, green
and blue peaks are near the left side, this image looked wonderful.

Rick
----- Original Message -----
From: "Siegfried" <siegburg@whooshnet.com>
To: <astro-photo@seds.org>
Sent: Tuesday, September 25, 2001 8:45 AM
Subject: [APML] Im Blue


After processing some images from the other night, they all turned out to
have a very blue/violet shift.

Now let me just say that the humidity was 100% (at least, heh)...I am aware
that humidity will affect film, and have ordered all the parts for a gas
purge system.

I have been trying out the Fuji Super 800 film the last couple sessions, and
have been generally pleased with it cause it picks up stuff fast, I like
that because im still new to all this. But these images are far more "blue"
then any other I have taken, so i'm left kinda wondering what happened. The
entire roll of film, which includes some planetary exposures under 2 seconds
is the same - a blue tint everywhere (when scanned, prints are ok). I should
also note that this was my 1st attempt at exposures over 1/2 hr.

http://wsphotofews.excite.com/038/qI/h9/J1/fA16935.jpg

I have my negative film processed at a lab...so I'm wondering if this a
result of bad film, processing, scanning (the prints came out looking ok).

On another note, after looking at the scanned images in PhotoShop it seems
the blue channel contains all the "sky fog / film grain" (however badly
discolored it is), so I'm thinking that this layer of the film is more
susceptible to the extreme humidities...is this possible? But this doesn't
explain why the short exposures are blue also. When I rescanned the images
and adjusted the curves so as not to pick up so much blue the situation
improves, but I'm left feeling something weird was going on here. Must the
color curves be manipulated when scanning, is this the proper technique?

Also let me just say thanks to those who started the thread about the STV
and tweaking the settings so as not to "chase the seeing", the guiding
tolerances with my Gt1 have improved dramatically.








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