Re: [APML] Cygnus on E100S

["D. Kodama" <kodama@alumni.caltech.edu>]

So are you ending up with a rectangle with just the corners rounded as
opposed to a circle with flat top and bottom (for landscape orientation of
the original frame)?  If you have an example of how you've done it, I'd be
interested to see it.

Thanks for the input!

Dave K.


>
> Dave,
>
> As a widefield fan, I love everything I've seen produced by these Borg
> f4 systems - especially by you and by Jon Kolb. You have really brought
> it to the max with that 4x5 inch camera.
>
> My advice on the nicest presentation would be:
> 1) Flatfield-correct the vignetting where it is moderate (down to say
> 50% illumination). This will maximise the FOV impact.
> 2) Establish the centre & radius of the vignetting falloff, and do a
> hard circular crop of everything beyond the radius where the image
> flatfielding ceases to be acceptable
> 3) Do a rectangular crop on what's left to make the circle symmetric
> from left-right (and optionally from top-bottom).
>
> This will give you a nice flat image containing as much FOV as possible,
> with a sharp-edged framing & aestherically symmetric rounded corners.
>
> Ray "who does this with 6x4.5cm shots vignetted through a 2-inch
> focuser" Butler
>
>
> D. Kodama wrote:
>
>>Hello,
>>
>>I've been trying to dial in my large format shots with E100S.  This is a
>>full-frame 4x5 test from last weekend:
>>
>>  http://www.eanet.com/kodama/astro/2005/0813/index.htm
>>
>>I will probably try exposing longer next time, but I was very pleased
>> with
>>the color balance at this exposure (30 minutes).  I did no color
>>adjustment at all.  The only photoshop processing was a curve adjustment.
>>Too bad E100S is obsolete.  :(
>>
>>Given the vignetting, I'm interested to hear if you prefer to see:
>>
>>  - the whole frame
>>  - rectangular crop to unvignetted area
>>  - circular (oval) hard frame
>>
>>Thanks,
>>
>>Dave Kodama
>>
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>>
>>
>
>
> --
> Dr. Ray Butler
> Lecturer, Physics Department & Computational Astrophysics Laboratory,
> National University of Ireland - Galway,
> University Road, Galway, Ireland.
> Web: www.nuigalway.ie/physics/ 	Email: ray.butler-AT-nuigalway.ie
> Tel: +353-91-493788 		FAX: +353-91-494584
>
>
>
>

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