I have had several discussions with friends in Thailand and England about this, and have experienced that depending on how they are used, the results can be unnatural. She's Lazy She pursued the cause, but she was lazy to find the right parameters every time, but she was hit by a Japanese senior So she started researching solutions in earnest.
The first photo is the photo I shared the other day, and there are two problems here.
(1) I see something that should not be there. In most cases, there is a molding like an octopus sucker.
(This is caused by blur processing or sharpening processing)
(2) It looks like the light part of the object is blurred.
(This happens in Denoise processing)
Regarding (1), I compared NASA's M51 and my M51 at 300% magnification and found several octopus suckers that were invisible in NASA but visible in my photo. Her senior pointed out, "There's a dark belt that I've never seen before," but she couldn't find it.
I immediately started editing from the stacked photos, and did a 300% comparison check after Blur processing, but there was no octopus sucker there. Blur is innocent this time. Next, when I checked the comparison after processing with the sharpening function that I usually use, there was an octopus sucker. This is the culprit. When I changed the tool and processed it with ADVShrpening in Script, the sucker of the octopus disappeared.
As for (2), it did not occur in Denoise in Liner processing. Denoise with Noneliner resulted in blurry areas. That's the cause, but the solution isn't that simple. There is no problem in areas with high brightness and contrast, but it occurs at points with low brightness and contrast. Well, it's natural because it's DeNoise processing. I tried many different patterns of Denoise parameters in Noneliner, but it didn't work. I went back to the original and greatly weakened the DeNoise parameter in Liner, and tried various Denoise parameters in Noneliner again, and the blurriness improved considerably. Of course the noise increased at the counter. It's still blurry in the faint parts to the north and south. After all, that part was partially raised in brightness, so I thought that was the cause, and when I performed Denoise processing without changing the brightness there, the blur subsided (or rather, the cause of the blur disappeared). I became empty at the street counter.
(1) The phenomenon of seeing strange things can be solved by changing the Sharpening function or by changing parameters if it occurs in the future.