RE: [APML]: Second HP v. Kodak Test

[Benjamin Gomes-Casseres <ben@alliancerevolution.com>]

David:

I guess it is more pervasive than just my negative edge. What I mean by 
"chromatic aberration" is that using very high magnification on bright star 
images you see reddish pixels on the edge of the white blob and bluish 
pixels on the opposite edge of the same blob. This is not visible in the 
Kodak scan and is therefore not produced by my photographic equipment (a 
well-corrected refractor). You can see this effect by magnifying the stars 
in the top right corner of the M20 images. Compare the Kodak and HP images.

Do you think this is simply the optics in the HP or negative curling?

Thanks for your feedback and help!

Ben



-----Original Message-----
From:   D. Kodama [SMTP:kodama@alumni.caltech.edu]
Sent:   Thursday, January 22, 1998 1:26 PM
To:     astro-photo@nightsky.com
Subject:        Re: [APML]: Second HP v. Kodak Test


Dave Kodama wrote:
>
Ben,

I had another thought about the "chromatic aberration" you
are seeing.  After re-reading your writeup on the web page,
you said it was visible at the edges of the original
negative.  I've also seen what I call a color shift when
the contrast is pushed way up.  Since this seems to occur
along the long edges of my negatives, I think this is due
to curling of the negative.  I don't know if it's possible
to do something to hold your negative flatter, but you
might try something along those lines.

Dave