A New Way to Detect PWM?

LED Flashlights – General Info
1

After baking my trusty P7 last night, I was trying to improve the pictures from my iPhone and I happened to shine one of my flashlights on the P7 in low in an attempt to keep the flash from going off. This is what came up:

I had heard of using hand in front of the lamp, shining it on a fan or showerhead, but never heard of this. I tried it on several other lights and got the same thing, but only on some and usually only in low mode. Image appears on the iPhone preview as well as in the final picture:

P7 C8

Yezl Z1

UniqueFire 3900

Solarforce M8

Is this something new or just new to me?

2

Yes, it's already been known that PWM would show up as banding on video, esp for cams with a "rolling shutter".

3

I'm not even slightly bothered by PWM but it is very noticeable on the camera screen - on any camera I've tried. I've not seen it in the actual pictures though.

4

I figured you would know 2100. I have seen this with a video cam pointed to a CRT monitor or a TV screen before.

Thanks!

5

thanks, nice trick!

the easiest way to detect PWM is not with hands or white walls but with the light itself. in a completely dark room shine in any direction. look at the beam path from the side. then begin to move the arm (with torch in the hand) up and down in vigorous waves. continue to look at the beam (Not into the beam! ouch) from the side. The faster you wave/move/shake your arm, the better.

i am not sure if iTP A3's PWM is considered high-frecuency. but i can readily see that it's there.

6

that sounds like a lot of work for "easiest".

i think i'll stick to the running water test, fan test, or the camera test.

7

i dont possess cam nor a fan.

running water test .. never tried it before. if i am in a dark room and want to check, there is no shower.

:D

8

My dogs show pwm with their white tip tails.

9

when they're wagging with the tails?

fast wagging would be required.

must look funny when your dogs wag :bigsmile:

10

When I saw the first picture, I thought you had the light resting on some display paneling like used in stores that allow the hangers to be moved into different positions. I was trying to figure out what was wrong with the picture! Embarassed

11

But not as funny as imagining you walking around flapping your arms in a Dark room.

12

Maratac AAA / iTP A3 XP-E Q5 low PWM ~200Hz, iTP A3 XP-G R5 high PWM ~2.4 kHz

13

now this is getting funny *here* lol :evil:

thanks Vectrex. mine is definitely XP-G R5 (i can tell from emitter built), and i can see the frecuency with my flapping arms technique!!

14

Your E09 should have a much slower PWM

15

very much slower, true!! :)

wanna trade? your Brinyte with one of my many E09's? ;)

16

Nope... I like the undetectable PWM levels of the Brinyte ... but can hear the PWM if I hold it close to my ear... maybe one could use an electronic guitar tuner to get the Hz numbers?

17

Pop open the hood on your car at night, have the engine idling. Shine a light (that has PWM) on the pulleys. You will be amazed.

18

CPU fans work great also.... I like the spinning backwards effect, if the frequencies match up nicely.

19

I might be one of the lucky ones who don't notice the PWN but on some really slow frequency ones, as the TR1200 on med and low modes.

Anyway, if you have to do all those tests, I understand it does not annoy you that much, does it?

20

I'm with you, I've never noticed PWM visually unless I was looking for it...ie shine it at a fan, or at night when I turn the faucet on. I've never understood why some people are so upset about it, maybe I'm just not getting it...do people actually see the ocillation with their eyes, while not testing for it? I understand the buzzing can be annoying however.