I often hear people suggest the shower test as a way to detect whether a light uses PWM or if it delivers constant current. The test is: Shine the light at fast-moving water, like a shower head. Then look for dotted lines. If it has dots or spots, it uses PWM. If the streaks are smooth, it’s constant current.
But I find the test unreliable and error-prone. So I took some pictures of how this test looks in real life, and I want to know if people can determine the correct answer.
Here’s the pic. The poll choices refer to this picture:
Both lights were running at 30 lm, and both pictures used the same camera settings. Clicking the picture provides a larger version.
If the only light source on rhe shower has PWM you should see it in all water beams, not just in some. So in both pictures the shower is illuminated with a non-PWM light source, or too fast to even notice this way.
I have trouble telling from that photo. I use a bicycle hanging in the garage; spin the front wheel and shine the light at the spokes. The bike is always there unless it is being ridden. If it’s being ridden I probably have little interest in checking PWM right then.
I think TK is playing a trick on us and one or both are not using PWM. I would normally say right and left is both PWM, but I think the trick is left is no PWM and right is PWM. Possibly no PWM at all.
I use the manual control on my camera/phone camera to check for any “flickering”, normally between 1/1000 to 1/2000 exposure the “flickering” will show clearly. I’m awfully sensitive to mid to low frequency “flickering”, even those that claims by some as “high-enough” or not PWM in its strict sense. For me, it doesn’t matter whether it’s On-Off or “Stay-On but does square wave”, as long as it’s not constant current, it’s being put to “flickering” category for me.
It’s like there’s 2 light sources. I get that the water droplets can move at different speeds which isn’t accurately represented with a still picture. But as pointed out by TK it seems like a pretty flawed test.