The Shower Test - can you spot PWM?

For the poll would “PWM” be any at all, or PWM at a frequency slow enough for a human eye to see it?

Any PWM at all.

But, specifically, the kind which pulses on and off. Not the kind which stays on but does a square wave oscillation between two different levels.

I voted left=constant, right=pwm. But I’m really unsure.

Norman Bates would know.

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 can't tell. I'd use a control picture as reference, and compare, if this were my test.

To test for visible PWM, I use a fan. After that, I use a camera with very short exposure time ;)

Streaks and dots in both pics to me :question:

This…

It is.

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. :smiley:

yup both have PWM but the right pic is worst :slight_smile:

…and what about the streaks?

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.

oh I didnt see that :stuck_out_tongue:

I shine a light at my spinning usb fan to test for pwm. Works well

Is it just me, or is there a face in the water on the right side? Creepy! :open_mouth:

There is a face there for sure.

Looks kinda like a caricature of Stan Laurel with his little hat.

Kind of a mirror-image of

Anyhoo, when I put my face close, stare at the image, and kinda go cross-eyed, I kinda see a 3D image of a swan.

The dots in the second picture aren’t necessarily PWM, they just look like the “ripples” in a stream of water reflecting light at different angles to me.

all you have to do is wave your finger back and forth rapidly, in the beam

or point at a rotating ceiling fan

wle

There’s zero chance someone will be able to see 10kHz or faster PWM doing that.

Fast movement of light source - the best PWM test.

maybe but

a. at that frequency, isn;t it imperceptible?
b. would the shower test work for that, assuming PCM/no PCM matters at that frequency?