This would seem to be a most UNlikely result if done "live"

Bacground over foreground and no apparent mixing even at boundaries.
This very strongly suggests it was done in post processing.

Also, the smooth radius change curve does not feel likely to be "natural". When swept in large arc the arm not only changes length as it moves but also the rate of change of length with position & times varies between locations as the arm geometry changes.

I have some swept arm arc time exposure of people waving "sparklers". I'll post one when/if they show up to allow comparison of arc shapes.

More soon.

This would seem to be a most UNlikely result if done "live"

Bacground over foreground and no apparent mixing even at boundaries.
This very strongly suggests it was done in post processing.

Also, the smooth radius change curve does not feel likely to be "natural". When swept in large arc the arm not only changes length as it moves but also the rate of change of length with position & times varies between locations as the arm geometry changes.

I have some swept arm arc time exposure of people waving "sparklers". I'll post one when/if they show up to allow comparison of arc shapes.

Sparkler arc - full 'circle' in this case.
More circular that I'd recalled but not the perfect arc of the photo above.
Also does not include any of the background hanging over the foreground as theirs does :-).
No post-processing additions in this one :-).
Chinese New Year, Ningbo, China:

This would seem to be a most likely result if done "live"

Bacground over foreground and no apparent mixing even at boundaries.

More soon.

This would seem to be a most UNlikely result if done "live"

Bacground over foreground and no apparent mixing even at boundaries.
This very strongly suggests it was done in post processing.

Also, the smooth radius change curve does not feel likely to be "natural". When swept in large arc the arm not only changes length as it moves but also the rate of change of length with position & times varies between locations as the arm geometry changes.

I have some swept arm arc time exposure of people waving "sparklers". I'll post one when/if they show up to allow comparison of arc shapes.

More soon.