Contrast Module Introduces Artifacts

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

Contrast Module Introduces Artifacts

Postby maxmayer » Mon Jul 09, 2018 9:15 am

Hi There,

I have been using ST for some time now and frequently came across an issue when using the contrast module. For some reason it shows a rectangular frame within the image that has a higher contrast on the inside and a lower contrast on the outside. The frame is roughly symmetrical. If I were to guess, I`d say that I am seeing my filter (EOS clip in) but I am not sure how that would be supposed to work. I don`t get this issue with all images and I cannot replicate it in Photoshop (i.e. apply harsh curve).

Example attached
Acquisition: 3x300sec (Test shots), stacked in DSS - darks, no flats
Equipment used: SW ED80, Canon EOS450D, STC Dual Band Filter (EOS clip in).

Any help narrowing this down would be much appreciated.

Cheers Max
Attachments
ST Contrast Artifact.jpg
ST Contrast Artifact.jpg (73.86 KiB) Viewed 320 times
maxmayer
 
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Re: Contrast Module Introduces Artifacts

Postby Rkonrad » Tue Jul 10, 2018 7:42 am

My guess is that before using "wipe", either your image wasn't cropped perfectly or you didn't set your dark anomaly setting aggressively enough. Mostly, wipe temporary stretch doesn’t give enough detail to see if the wipe was actually accurate. Interestingly enough, I seem to remember seeing a very similar structure to the irregularities displayed on your image-usually this is working with low snr data possibly in light pollution. It's usually cleared up by a simple vignette wipe on default settings. Since you have few light frames, I'm suggesting could try this. "Contrast" will enhance areas based on whatever data it is given - especially with a poor wipe.

I may to totally wrong but those are my instincts based on experience!

Richard
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Re: Contrast Module Introduces Artifacts

Postby maxmayer » Thu Jul 12, 2018 3:38 am

Hi Richard,

thank you for your analysis. I actually didn`t use Wipe as it produced even more bizarre results. I will however, follow your guide and try have a play with the dark anomaly settings in wipe and see, if I can get a decent outcome from the Wipe module before proceeding to Contrast.

Max
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