Photoshop - pixelate view after zooming

I'm drawing one pic and when I zoom I see pixelated view. It happens only in dark colors, those brighter looks better.

I'm not sure if only I can see this, maybe it's my monitor issue, but I checked on the second one and I can see the same.

It looks like gif.

I use soft brushes, not pencil or something. It's RGB, 300dpi, 16bits/channel

Any ideas how can I increase quality of the image? Or maybe you can't see this?