Originally posted by Kunzite Dear Rishi contacted the author which gladly obliged and updated his article:
"Update, June 19, 2018: A critical issue with the Pentax K-1 Mark II’s noise performance, particularly when stacking multi exposures was brought to my attention by Rishi Sanyal of DPReview.com. I have updated the verdict of my review accordingly and I have added an addendum to the “Image Quality; Noise” and modified the “Conclusion” section on this review."
The following words are apparently the meat of his change:
"
However, the issue does create that bizarre non-random grid pattern that’s visible under magnification. Astrophotographers hoping to stack multiple exposures should approach the K-1 Mark II with consideration of this issue and understand that the K-1 Mark II may not be as good of a choice versus its older and cheaper predecessor, the original K-1. If stacking astrophotos using Astrotracer on the K-1, photographers should consider capturing a large number of frames (greater than 8) and re-aligned them in post before combining them in to a stack. With enough variation between frames, artifacts can be averaged out. Note that this technique will not work on stacks of exposures that are already aligned such as foregrounds."
Then at the end he says:
"
It’s too bad that these excellent features are marred by Pentax’s poor implementation of a noise reduction algorithm. Astrotracer is particularly hindered by this issue if used for creating short stacks of exposures."
but he retained the words:
"At ISO settings higher than ISO 400, there is noticeable “baking” of the RAW file that reduces noise but also slightly affects fine detail. We did not feel that the noise reduction compromised the results of our single exposure photos in a very tangible way, we wish the behavior did not exist."