Processing Question: Where did the color go?

[barque]

I'm trying to up my processing game and learn more about PixInsight. Using some sample data posted by Jerry Lodriguss (http://www.astropix.com/html/i_astrop/practice_files.html), I used the batch preprocessing script to calibrate, align, and stack the data. After applying DBE, SCNR, and a screen stretch, the image is full of detail but the color is completely washed out. Some of the color comes back if I stretch the red channel or increase the saturation, but I am missing something in how to process.

By comparison, processing a single light frame via Adobe Camera Raw with a stretch in Photoshop shows that there's lots of color in the raw data. Can somebody please point me in the right direction to recover the color in PixInsight? Thanks!!

Rob

[pfile]

having to boost the saturation is totally normal... ACR is doing that for you behind the scenes.

rob

[sharkmelley]

I'm trying to up my processing game and learn more about PixInsight. Using some sample data posted by Jerry Lodriguss (http://www.astropix.com/html/i_astrop/practice_files.html), I used the batch preprocessing script to calibrate, align, and stack the data. After applying DBE, SCNR, and a screen stretch, the image is full of detail but the color is completely washed out. Some of the color comes back if I stretch the red channel or increase the saturation, but I am missing something in how to process.

By comparison, processing a single light frame via Adobe Camera Raw with a stretch in Photoshop shows that there's lots of color in the raw data. Can somebody please point me in the right direction to recover the color in PixInsight? Thanks!!

Rob

The stretching that ACR performs will maintain colour although the stretch in Photoshop that you subsequently perform will lose some of that saturation.  Generally speaking all stretching operations will lose saturation, including the screen stretch.  It's why I wrote the ArcsinhStretch module: https://pixinsight.com/doc/tools/ArcsinhStretch/ArcsinhStretch.html

It has been purposely designed to prevent the loss of saturation during the stretch.

Mark

[ChoJin]

arcsinh is indeed great for color preservation, but unfortunately like maskedstretch you lose contrast compared to a HT stretch

[barque]

Thanks all. Haven't completely figured out how to get all the color back (as I see in the ACR version) but I'll keep working on it!

[dpaul]

Hi Cho,

How about doing partially with Arcsinh and Histogram Transformation Stretch to get color and contrast?

Thanks

David

[RickS]

You can also boost saturation easily with a clipped lum mask and CurvesTransformation.

[dpaul]

thanks again Rick

David

[ChoJin]

@dpaul I'm currently experimenting with combining the arcsinh and HT stretches with a (star)mask and some pixel math magics (ideas taken from https://pixinsight.com/tutorials/NGC7023-HDR/index.html , the "High-Contrast, Small-Scale Structures" part). It seems to work great to get my star's shapes and colours back. They don't look like flat discs anymore.

I've also seen in another topic someone doing RGB stretch with arcsinh and L stretch with HT and LRGB combination to combine them. I haven't tried that yet.

[dpaul]

Thanks Cho

David