Spooky Rear Light

[needlongerlegs]

This is part of a hour long video,

The rear light is coming on and off

But you can't see this with the naked eye only on camera....

https://www.youtube.com/watch?v=DOWiBCUPZxs&feature=youtube_gdata_player

WTF is going on?

 

[GC6269]

I think LEDs pulse at a frequency imperceptible to the eye but certain cameras pick it up.

You see it often on Top Gear filming!

 

[mcinlb]

Possibly the canbus system carrying out a 'check' on the rear light i.e. not enough current to actually bring it on full

 

[Engineer]

This is part of a hour long video,

The rear light is coming on and off

But you can't see this with the naked eye only on camera....

https://www.youtube.com/watch?v=DOWiBCUPZxs&feature=youtube_gdata_player

WTF is going on?

Pulse modulation, lots of short duration high level current pulses give an apparent high brightness without over heating the LEDs - also one can change the width of the current pulses to vary the brightness (pulse width modulation PWM)

The pulse frequency is high enough that the 'latency' in the human eye cannot see the flickering but any instrument with a faster response can - similar effect to the flickering of older CRT TV's when you look out of the corner of your eye.


I could go on but I won't!

 

[needlongerlegs]

Pulse modulation, lots of short duration high level current pulses give an apparent high brightness without over heating the LEDs - also one can change the width of the current pulses to vary the brightness (pulse width modulation PWM)

The pulse frequency is high enough that the 'latency' in the human eye cannot see the flickering but any instrument with a faster response can - similar effect to the flickering of older CRT TV's when you look out of the corner of your eye.


I could go on but I won't!

Please do Mr Engineer, would like to understand it so we can tweak the camera, its real strange its so slow every ten seconds maybe...

 

[Ali-bear]

 

[Engineer]

Please do Mr Engineer, would like to understand it so we can tweak the camera, its real strange its so slow every ten seconds maybe...

Hmmmm not sure that you will be able to tweak the camera, you might try selecting a different resolution on the camera to see if the frequency changes, or buy another camera but don't think that you will ever get rid of it completely - it's related to the 'wagon wheels going backwards in films' effect if you are old enough to remember that

 

[Deleted account 240901001]

I liked Wagon Wheels.....don't see them about these days.....

 

[needlongerlegs]

Hmmmm not sure that you will be able to tweak the camera, you might try selecting a different resolution on the camera to see if the frequency changes, or buy another camera but don't think that you will ever get rid of it completely - it's related to the 'wagon wheels going backwards in films' effect if you are old enough to remember that

Yum Wagon Wheels .. used to have one of those and cup of Boveral after swimming club about fifty years ago LOL.

 

[mark2jag]

they aint Wagon wheels any more. Now they are skateboard wheels......

 

[JayC]

The pulse frequency is high enough that the 'latency' in the human eye cannot see the flickering but any instrument with a faster response can - similar effect to the flickering of older CRT TV's when you look out of the corner of your eye.

I could go on but I won't!

There is an exception to this , well , sort of (ish)

I am not the only person to notice that when following a vehicle with these lights on, and then divert your line of sight, perhaps moving your head to the left/right a tell tale witness of this pulsing can be detected in the peripheral vision.
There, not a lot of people know that, or indeed want to, but I bet some will try it!

 

[Engineer]

There is an exception to this , well , sort of (ish)

I am not the only person to notice that when following a vehicle with these lights on, and then divert your line of sight, perhaps moving your head to the left/right a tell tale witness of this pulsing can be detected in the peripheral vision.
There, not a lot of people know that, or indeed want to, but I bet some will try it!

I have noticed this too - it's cos one's peripheral vision is more sensitive to movement, we don't see colour but can detect fast movements out of the corners of our eyes - it's so we can spot nasty, scary bitey things creeping up on us.