During the day I study a number of digital photographs at 100 percent to look for noise in general.

#1
Sometimes I meet a deep blue sky shifting from one tone to a darker or lighter in a fractal-like pattern (see attached Tone_rendering_1). In .._1 the sky was intensified with a pol-filter.
Tone_rendering_2 is a very light area shifting over subtle tones of green. I have emphasized the "fractals" with Levels.

Click to view attachment
Click to view attachment

#2
Another remarkable effect is the shift from light to dark in a halo (no examples - I think you know). The tonal range seems to change in steps (zones) as if the cameras' sensor reacts in quantum leaps - creating concentric zones of equal density in stead of a smoothly graduated tonal range.

If someone could help with the right technical explanation to these phenomenons I would appreciate it very much.

It's a combination of JPEG artifacts and the limits of your monitor to display perfectly smooth gradients.

Hi Jonathan,
What are we talking about in resolution for an "unlimited" monitor?
Thought experiment: A new tiff file is made directly from raw. Will the gradients be displayed perfectly smooth on my new "unlimited" monitor?
My theory of the sensor cells reacting in quantum leaps will be proved wrong?

Yes. Most LCD monitors will exhibit some banding in certain color ranges because they are limited to 8-bits per channel. There are some monitors with internal 10-bit LUTs that can be hardware calibrated that do not have this problem, but they are much more expensive. They will display a smooth gradient as a smooth gradient.

Hi Jonathan,
Thank you - nice to know, when the bank opens ;O)