On Thu, 20 Dec 2018 09:36:02 -0000, Jon Fairbairn wrote:

"William Gothberg" "William writes:
Agreed. All I can detect (with my digital camera) is that
one brand of LED light I have flickers about 5 times less
(not sure if it's smother or faster) than the others.

Try a longer exposure and move the light rapidly relative to the
camera.

Good idea.

I just tried it with the best lamps I have, which show a slight variation in brightness at exactly 100Hz, which must be seeping through from the mains. However the LEDs never go off, they just change brightness by 8%.

With the worst lamp, same 100Hz, but they actually go right on and off, with a duty cycle of 0.6.

Am I right in thinking these aren't SMPS at all?