What I seek would be an image that shows that 16 bit editing has a clear advantage, when working in a normal gamut RGB space, such as Adobe RGB.
(...)
Anyone have an example like that?
I have.
I usually shoot HDR interiors by blending 3 bracketed images {-2,0,+2} corrected to initially have the same exposure as the least exposed shot, i.e. a very dark image. I then open it into PS and apply a lift curve, a contrast curve, and some local arrangements when needed.
The initial image is obtained in 16-bit and Adobe RGB with 2.2 gamma using
Zero Noise. That image needs to be very robust because shadows will be strongly lifted for tone mapping.
In 16-bit, these images are incredibly robust (I managed to lift
here one of them by +12 EV, see Fig. 11, and there was no posterization. Not even a 16-bit linear DNG would have resisted such an overexposure, see Fig. 12). The trick for that is that both exposure correction and 2.2 gamma are applied at the same time, in just one high precission floating point operation, then rounded to 16-bit integer (BTW real 16-bit, not 15-bit like in Adobe software), so it's impossible to have a richer image for that degree of exposure.
On the contrary in 8-bit, the resulting image shows clear posterization in the shadows after the tone mapping process in PS. These images are almost noise free thanks to the optimum bracketed blending, so shadow posterization becomes easily visible on a low bitdepth:
Sample scene:
16-bit vs 8-bit postprocessing (posterization in the wooden table left and chair back when initial image was 8-bit):
For those interested in looking at the curves applied:
capas.tif.
I know it's quite a extreme postprocessing, but just an example that I REALLY NEED 16 BIT for my interiors workflow.
BR