You looking at your image actual pixels in one cast and in the other cases you tooking at pixels in an image that was quickly scaled for the image your editing. You are comparing Apple to Oranges they not the same thing. They are two different images. Not even the same size.
Thanks for the quick reply. I understand, but how come that on 66% zoom it's still smooth, and 50% and anything below starts losing a details. From your reply above, I guess there's no way to make it looks smooth every time?
Photoshop quickly scales your image for performance some Zoom percentages look worse the other zoom percentages.
Exactly what I though, but wonder if there's a way to ignore performance optimization. Thanks for quick reply though.
Photoshop uses 8bits/channel for blending previews at less than 66% zoom. There is no way around that. It was probably done for speed in the past and although there is an argument that today's hardware should be capable, image sizes have also gotten larger and I have no idea how deeply embedded that code is and what the implications of updating it are.
Hence the advice always to view at 100% zoom to check blending.
Dave is right! Why the developers haven't fixed this yet is beyond me. It results/resulted in a lot of confusion among PS users, even to the point of users adding extra noise to get rid of the banding, which is of course unnecessary, and only serves to degrade the quality.
I believe the now-retired senior Photoshop developer Chris Cox implemented that code a long, long time ago when computers weren't that fast, and 16bpc processing and display caused performance/video memory problems.
A second, more worrisome aspect of Photoshop legacy 16bpc code base is that its 16bpc mode isn't actually a true 16bpc mode at all: it is a 15bpc mode. And when full-range 16bpc images are loaded, Photoshop will CLIP the original image to fit in a 15bpc value range. WITHOUT warning the user about this.
That is unforgivable in this day and age of HDR and 3D / effects imagery. And it ought to have been fixed by now, but it hasn't.
I think Mr. Cox's code is so deeply integrated in Photoshop's core, that it would potentially break large parts of its functionality, and other core features probably rely on it. So the developers might have decided to leave it as it is. Of course, this is pure speculation on my part.
Be that as it may, it is somewhat ridiculous that this is still an issue in 2018. Competing image editors (PhotoLine, Gimp, Affinity Photo, and any other 16bpc capable image editor or painting app) have no such issues. It really is time now for the Photoshop team to step up, and fix this. (As they should have fixed other long-standing problems: but that is a different story for a later time.)