shadow turns bad ...?

btride  wrote and i did not understand the way you check: "u can confirm whether the banding is in your document or display system if you run over the bands with the eyedropper tool"

Hi

Let me explain my comments.

We sometimes see banding on gradients due to the limited levels (i.e steps of brightness) available in 8 bits. There are only 256 steps from fully off black to fully on in each of the red , green and blue channels

This can be avoided by working in 16 bit which in theory gives 65536 levels (in Photoshop it actually uses 32769 levels). This increase in steps is more than enough to make the individual steps invisible.  Note this will only work for gradients added in 16 bit. Just converting an 8 bit stepped gradient to 16 bit will keep those steps.*

When using 16 bit documents,  the display system still operates at 8 bit. So a gradient may appear to be banded, when in actual fact it is not. If you switch the info panel to show 16 bit levels, then move slowly across the apparent banding, it should show constantly changing values - not the stepped changes you will see if the banding is in the document.

*The other way to hide banding in an existing gradient is to add a little noise to the picture (Filter >Add noise). Although it sounds counter-intuitive to add degradation to hide an artefact, it takes very little noise to hide the banding effects on a gradient and is often much preferable to the visible banding.

Dave