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Discussion Starter #1 (Edited)
Noticed 2 years ago in my video below, taken with a camera by MK when I got my Kleemann ECU tune and headers that at about the 21 second mark, my rear LEDS appeared to be blinking


A little bit of explanation is here:

When the presenters are showing a car, they often use slow-motion effects. When they do, the LEDs appear to blink. Why does that happen?

I'm pretty sure all LEDs flash or blink, just at a rate that the human eye can't register. When you capture them on camera, the LEDs natural frequency is out of sync with the camera's shutter/frame rate, which is why the LEDs appear to blink.


This is the same reason why, on camera, it can appear as though a car wheel is spinning backwards, or helicopter blades are standing still. The rotation versus the frame rate will capture the images in different spots.
You can see the same type of effect by pointing a camera at a CRT TV or monitor.
 

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As mentioned, it's not the slow motion that makes them blink but the ratio of the blink rate vs the frame rate of the camera. Same principle as a strobe-light in a dark nightclub.

On the SLK the tail light LEDs blink at a rate of about 115Hz and an on-percentage of about 7%.

You will notice near the end of your video, when you press the brake, they will not longer appear to blink, because they indeed do not. When braking the SLK's tail lights come on 100% of the time.

A picture of the electrical pulse driving the tail lights on the SLK. You can see it is mostly down, with short spikes upward:

 

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Discussion Starter #4

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Discussion Starter #6
That is why I posted it :D
Thought you knew me by now?
 

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On the SLK the tail light LEDs blink at a rate of about 115Hz and an on-percentage of about 7%.
The technique is called Pulse Width Modulation. It's an easy way to dim LEDs without expensive electronics. You repeatedly turn an LED on for a short time and off for a longer time and the LED (brake lights and DRLs) appear dim. If you repeatedly turn the LED on for a longer time and off for a shorter time the LED appears brighter. This on/off time ratio is called the mark:space ratio.

As @Durknation says, this repetition is at about 115 times a second (115Hz) and which is fine for most people but bloody annoying for me. I am one of those unlucky souls who can see the flashing of Mercedes / Audi (and particularly Peugeot - a French car make). Even DRLs fitted to most modern cars are switched this way - usually so they can be dimmed when the driver signals his intention to turn.
 
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