Ultra slow motion and flashlights

Kitchen Panda

Enlightened
Joined
Aug 28, 2011
Messages
260
Location
Winnipeg
I just found out last week that my point-and-shoot digital camera has an "ultra slow motion" video mode (just one of the new features I got for buying my first new digicam in 10 years).

Aside from general foolishness, I found some flashlight-related uses for it as well.

1. The Fenix TK 70 shows no sign of PWM at any level, according to the slow-motion playback.

The strobe mode is nice and clear,taking only 1 or 2 frames to go between on and off. The camera claims 240 frames/second in slow motion mode. The SOS is also very crisp.

2. The Quark AA "beacon" flash really is as fuzzy-edged as it seems. There's a slow build-up over 2-4 frames, then for about 5 or 6 frames its moderately bright, then it dips way down again for a few frames and then builds up. It's apparently steady for the next 80 or 90 frames, then fades out over 3 or 4 frames at the end of each pulse.

3. The Titanium Innovations CA1 is the only light I have so far that has any detectable inductor noise and a slight trace of PWM. Playing back the ultra-slow-motion video, I see a little "bar" across the middle of the image, rather like a TV set with the vertical hold out of adjustment (only the old-timers will remember that!). The bar disappears at full output.

4. The Fenix HP11 headlamp again shows no sign of PWM playing back the video. The strobe mode has a similar rise and fall time to the TK 70, with build-up visible over 1 or 2 frames in playback.

Heaps of fun. While this camera won't do any Mythbusters-style bullet stopping (even a slow bullet would be clean through the field of view in two frames at 240 fps), it's been fun looking at dripping water, etc. - and as soon as I find some balloons I'm going to try popping one to see what it looks like. That was the original reason for checking the flashlights...I wanted to see if they would give any detectable flicker in slow motion. The under-cabinet LED lights in the kitchen pulse visibly in slow-mo.

Bill
 

tolkaze

Enlightened
Joined
Aug 26, 2009
Messages
569
Location
Muswellbrook
are the images sharp and in focus, if the images are sharp, and the camera is genuinly doing 240fps, it wouldn't be hard to determine fairly accurately the level of PWM, and if the PWM is a complete on/off cycle (I suspect a few of my cheapies are PWM but have some kind of power fluctuation like a power leak...)

You can also check PWM on a still camera, open shutter on long exposure, then wave the light past the lens and close the shutter... series of dots means PWM, the larger the gap, the worse the PWM
 
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