Update: ISO 3200 test follows below.

I just picked up a new Nikon Z7 and there have been multiple reports of banding in recovered shadow areas.  I decided to test this for myself to see when the problem might crop up.  I shot a desk in my office with a monitor (seems to show up more on flat black surfaces).  There was a lot of back light so the monitor is underexposed even in the 0EV frame.  Settings:

• RAW (NEF)
• Processed by Adobe Lightroom Classic CC 7.5 (Camera Raw 10.5)
• No processing except:
  • Profile: Adobe Color
  • White Balance: Daylight
• Exposure settings for each photo noted below.

TL;DR:

• Banding is an issue for files pushed +4EV or greater.
• Banding is not visible at normal viewing sizes.
• Noise reduction can smooth out the banding effect.

100% crop from the above image in the top right corner of the monitor.  No visible banding (as expected)

 

I then took another shot, this time with exposure compensation at -3EV, resulting shot is definitely underexposed.

The underexposed file then pushed in Lightroom to +3EV (exposure was the only adjustment).  Resulting image:

100% crop from the +3 push.  No visible banding.

 

The underexposed file then pushed in Lightroom to +4EV (exposure was the only adjustment).  Resulting image:

100% crop from +4 EV push.  No visible banding in the deep shadows.

However, I did see some banding crop up in some of the transition areas (light to dark) at the bottom of the monitor.  It’s slight but visible at 100%.

 

Finally, I did a +5EV push of the underexposed image.  This is now very over exposed and not usable but useful for testing.

100% crop from the +5EV image.  It’s slightly visible when I check at 100% in Lightroom but might not come across in the exported jpg very well.

As before, most visible in the light to dark transition areas.  100% below.

 

Looking in other areas of the image (not just the black monitor), I can see slight banding in the +4EV and +5EV pushed images.  Typically when you bump up shadows you introduce noise and in many cases some noise reduction is warranted.  I observed that adding noise reduction smoothed out the effect of the banding, though it was still present.  Further, the banding isn’t visible at normal viewing sizes and only becomes visible as you zoom in (50% or larger viewing sizes).  For print, this would translate to 14 inches on the long edge assuming no crop and 300dpi.  Anything smaller and I suspect it wouldn’t be visible.

For me, I can’t remember ever pushing files to +4EV or greater.  If I see a very high contrast scene I will often do some exposure bracketing so that I can capture detail in the shadows without pushing the file in post.  I’ll then blend the images for best results, and that type of workflow should avoid banding (I’ll test this in the future).  If I have to push files that far, they are likely just casual shots I’ll post on facebook and none of my friends would know the difference.  For me, this banding is a non issue.

Banding Test at ISO 3200

After posting some examples at base ISO (64) , a comment was made that the banding would become visible with less drastic editing if a higher ISO was used.  I decided to test this by shooting the same scene at ISO3200.  Results are below.

TL;DR:

• My testing show that banding is NOT visible at ISO3200 regardless of how much the file is pushed in Lightroom.  I think the noise at higher ISO will mask any banding present.

First, normal exposure (exposure comp at 0EV).  The scene has fairly extreme contrast between light (bright sunlight outside) and dark (no interior lights on, black monitor).

 

Now the same scene but camera has exposure compensation set to -3EV

Pushing the underexposed file by +3EV in Lightroom

 

100% crop from the +3EV push.  I’m unable to find any visible banding in the image.

 

Now a +5EV push of the underexposed file.  I find the file far too noisy to be useful so this is just an academic exercise to understand the behaviour of the sensor.

 

100% crop from the +5EV push.  It’s ugly but I don’t see banding, just a lot of noise.

 

Finally, I tried some editing the ‘properly’ exposed file (0EV) using highlight and shadow recovery.  Here the exposure is adjusted to +1EV, shadows at +100, hightlights at -100.

100% crop from the edited file, no visible banding.  I checked the whole image and could not detect banding anywhere.

 

My conclusion is that high ISO noise masks banding and, at least for ISO 3200, banding will not be an issue in editing (noise will be, as it is with any other sensor).  I might do more testing in the future to get an idea at which ISO the banding starts to become less noticeable.