Re: [APML] What's the Best Way to "Combine" Two Images ofDiffering Times?

[Jerry Lodriguss <lists4@astropix.com>]

Hi Wade,

You can use masks in Photoshop:

http://www.astropix.com/HTML/J_DIGIT/LAYMASK.HTM

Or, you can use Photoshop CS2's new High Dynamic Range function:

http://www.astropix.com/HTML/J_DIGIT/PS_HDR.HTM

Jerry




At 12:23 AM 9/20/2005, you wrote:
>For bright objects, such as M42, it is a known fact that combining
>several images at various times helps in getting the full dynamic
>range of this nebula; however, I'm not quite sure what's the best
>way to go about this.  I have Registar, but none of the Functions to
>apply seem like the "perfect" choice.  I feel using them will either
>destroy the shadows or the highlights.  I see that many recommend
>using Ray Gralak's Sigma function; unfortunately, he recommends one
>should have ten or more images to combine for "best" results.
>There's no way I can get 10 shots since each film shot ranges from
>30 minutes to 3 1/2 hours.  Anybody have a proven technique to get
>the most out two or more images exposed differently?  For example,
>let's say I take three images of M42 at F/5.0: one 30 minute, one 90
>minute, and one 180 minute.  What's the best way to get the full
>dynamic range of these images (i.e. visible structure from the
>center of M42 to its faintest extensions?  Any suggestions or
>comments would be greatly appreciated.
>
>Thanks in advance,
>
>Wade
>
>
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Photoshop for Astrophotographers
http://www.astropix.com/PFA/PFA.HTM










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