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Date: 01/08/17 07:31
Portland's MAX in SlowMoSnow
Author: F40PHR231

Threw together a quick video featuring slow-mo shots of Portland's MAX light-rail in the snow.

Highspeed video captured with Sony RX100IV point-n-shoot camera.

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Date: 01/08/17 09:44
Re: Portland's MAX in SlowMoSnow
Author: mapboy

What a clever video!  I'm surprised with the large size of the snowflakes that it isn't a whiteout in some of the scenes.  Why is the streetcar roll sign flashing (changing?) in some scenes but not others?  I haven't noticed anywhere else lights around tree trunks flashing at high speed like that.

mapboy



Date: 01/08/17 09:56
Re: Portland's MAX in SlowMoSnow
Author: Mudrock

Very creative video Chris. I enjoyed all the snowflakes and lights on the trees plus your slow motion.


Chris



Date: 01/08/17 10:28
Re: Portland's MAX in SlowMoSnow
Author: F40PHR231

mapboy Wrote:
> Why is the streetcar roll sign flashing (changing?) in some
> scenes but not others?  I haven't noticed
> anywhere else lights around tree trunks flashing
> at high speed like that.

All electric lights, including the screen you're reading this on as well as the lamp on your desk, flash in one way or another, and are engineered to flash at a frequency known as the flicker fusion threshold that our brain interprets to be a steady beam of light. It's great for us humans, but not so great for animals as some have brains that observe life at a higher frequency, so our streets, homes and anything electronic look like a giant epileptic-inducing rave to them (just like what you see in the video).

Light Emitting Diodes are sharper and easier to detect with a camera, especially when the camera's shutter rate is faster than the LED frequency. As railroads upgrade to LED headlights, more photos will be showing what appears to be a burned out headlight or ditchlight where in reality the camera's shutter was shorter than the light's frequency and activated while the light was in between cycles. The roll signs that don't appear to be flashing are mylar and use fluorescent bulbs for illumination. Keep in mind this bulb is still flashing, but light continues to linger in between cycles. The 'roll' sign that flashes noticeably is an LED destination sign, and since the camera is recording at a higher speed than the frequency of the LEDs, it captures the downtime of no light in between cycles. Same for the LED lights on the trees.

Attached is an example of how different incandescent and LED bulbs appear in a long-exposed image using similar photo settings and train speed. The lights in both top and bottom images are flashing at the same frequency, but the incandescent bulbs in the top image have lingering heat from the filament during the 'off' time in between cycles, so it continues to glow and give an appearance of being constantly on. The LEDs in the bottom image have no lingering heat in between cycles, so there is no light, which ends up creating a dotted pattern of motion across the image.

I hope future video editing programs will have a plug-in feature that addresses the issue of LED flicker by analyzing what the lights are composing and filling in the blanks so they appear to be stable.



Edited 1 time(s). Last edit at 01/08/17 10:58 by F40PHR231.




Date: 01/08/17 10:46
Re: Portland's MAX in SlowMoSnow
Author: railstiesballast

Learn something every day!



Date: 01/08/17 17:02
Re: Portland's MAX in SlowMoSnow
Author: stevewa

Very nice illustration...sometimes you can catch this from a moving LED if you are looking with peripheral vision, if you're focused on it your mind's persistence trickery prevents it...



Date: 01/08/17 20:32
Re: Portland's MAX in SlowMoSnow
Author: wa4umr

Creative video.  Thanks for posting.

I've tried to explain the "flicker" before but you illustration does a better job than I coud do with workds.

John
 



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