working with contrast

Questions and answers about processing in StarTools and how to accomplish certain tasks.

working with contrast

Postby Rkonrad » Tue Dec 06, 2016 4:25 am

I love the intelligence of the "contrast" module in Startools. There are times, however when I feel I'd like to be in more control of it - of course, I could well not completely know what I am doing. The examples below is from data, most generously shared by Scott Rosen (http://www.astronomersdoitinthedark.com/) of LDN1235 (Dark Shark). I have worked with this image in three layer: stars, nebula and star glow, starless. I'm reasonably happy with the result but feel it could be better if I could manipulate contrast on the starless layer more subtlety. I've tried making adjustments with the contrast module but always come up with something radically different than the original making blotches and hard lines rather than mild changes to the black and white. Am I using the module incorrectly for this or is there another way of achieving what I want within startools? I find that I usually end up moving over to software like Darktable to do a lowpass overlay to get what I want. Anyway, after I have blended the layers together, I worked with the oontrast module and it does a much better job but it also seems to wipe out some of the great nebulocity that is apparent in the starless image. These are links to the final result and then the starless image. Thanks in advance.

Richard

https://www.flickr.com/gp/rkonrad/Z7u850

https://www.flickr.com/gp/rkonrad/g01D2a
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Re: working with contrast

Postby admin » Fri Dec 23, 2016 6:17 am

Hi Richard,

Nice to see some pretty advanced processing there - making different layers.
The Contrast module is meant for medium to large areas, more suited to narrower fields and close-ups.
Scott's wonderful data is more of a wide field, possibly more suited to applications of the HDR and Wavelet modules which operate more locally and on smaller structures than the Contrast module can (effectively) target.

You can make the Contrast module work on smaller scales as well by increasing the Aggressiveness, but it's a bit of a jack hammer where perhaps a more surgical instrument may be warranted.

In the end, much of it is up to individual taste of course...
Ivo Jager
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