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Old 04-10-2019, 05:42 PM
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codemonkey (Lee)
Lee "Wormsy" Borsboom

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Join Date: Jul 2013
Location: Kilcoy, QLD
Posts: 2,056
PCC - does it give *correct* results?

I created a thread recently regarding PCC and the impact that deconvolution has on it, but Colin's recent NGC 253 image has inspired me to make another related topic.

In my previous thread I noted that PCC gives different results with the same settings, on the same data, if you but deconvolve the data before applying PCC.

Looking at Colin's image, I noticed it was very orange. I know that my image was much more blue, but I used the old ColorCalibration script plus a few tweaks so that's to be expected. Even though I used ColorCalibration in my image, I did try PCC first and didn't think the result looked like Colin's image so I tried it again... the result is attached here, see Colin's thread for his. Both used PCC with average spiral white reference.

I tried to very roughly approximate Colin's processing in the image I present here, but of course they're non-linear images that were processed differently. In addition, Colin's was OSC and mine was mono RGB.

So... should PCC give the same colour for the same target? It's supposed to be an objective method of colour calibration, so what's with the variations? I used to think PCC gave the correct results and that maybe they weren't what we're used to, or what we find most aesthetically pleasing, but they were correct... now I'm not so sure.
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