Re: [APML] M35 (exposure times) + experiment

[Roland Roberts <roland@astrofoto.org>]

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>>>>> "bl" == Brian Larmay <astrobri@ameritech.net> writes:

    bl> Hey guys, after reading this thread for awhile, I was
    bl> wondering if you guys wanted to compare raw scans.

We could do that, and it would be interesting, but....

The biggest caveat is scanner differences.  I have an Epson 2450,
which is a flatbed with a transparency adapter.  It's a decent scanner
and hard to beat if you need a flatbed and want the option for
medium/large format negatives.  But my guess is that it doesn't get as
much out of the shadows as a dedicated slide scanner.  I have an old
shot of Cygnus that a local photo shop did a great job on.  It was
horribly underexposed (4 min @ f/4) slide -> negative -> print
conversion did a good job of drawing out the Milky Way and even the NA
nebula.  I can't get much of anything out of my scanner.

    bl> Ill post two later whe I get home from work just so that you
    bl> can see what I get as far as an exposure of 7- 12 mins at f/4
    bl> using E200 and provia 400F.  Yall can edit them and post your
    bl> results..I hope even to learn some techniques that I might not
    bl> have thought of to apply to my work.

Well, I can tell you the procedure I generally use for my
constellation shots---it's not really a secret :-)

    o Crop and trim to remove any border from the scan.

    o Level adjustment---move the black and white points to be at or
      very near the darkest and brightest point of the scan.

    o If there is any sky glow and if the photo does not include a
      large amount of nebulosity, try a Gaussian blur or median filter
      with a large radius as a synthetic "dark frame."

    o Apply a mild unsharp mask.  Exact values will depend on the
      photo and the scan resolution....

    o Boost the mid-tones---can do either via "curves" for manual
      control, or via PWP menu Transformations -> Gray -> Levels and
      Color.

    o Maybe mess with the saturation.  With PWP, this can be done at
      the same time as the previous step.

    o Go back and play with all the above until you're happy or can't
      stand it any more.


    bl> Just one question before I post these though....  Should I
    bl> post these as tiffs or high res jpegs

I've got 1.5 Mbs download speed, so I can tolerate as much as you are
willing to allow for the download.

regards,

roland
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		       PGP Key ID: 66 BC 3B CD
Roland B. Roberts, PhD                             RL Enterprises
roland@rlenter.com                            6818 Madeline Court
roland@astrofoto.org                           Brooklyn, NY 11220

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