Motoring Discussion > Modulated lights on Top Gear/Fifth gear Miscellaneous
Thread Author: a900ss Replies: 18
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New Sun 11 Mar 12 21:11 
 Modulated lights on Top Gear/Fifth gear - a900ss
When top gear/fifth gear test a car on the track, often the brake lights and/or headlights modulate.

Is that something they do to the cars, flicker from the refresh speed of TV or something else?

Thanks in advance.
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New Sun 11 Mar 12 21:15 
 Modulated lights on Top Gear/Fifth gear - Old Navy
Could it be something to do with the "bouncing LED effect" discussed here some time ago?
Last edited by: Old Navy on Sun 11 Mar 12 at 21:19
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New Sun 11 Mar 12 21:23 
 Modulated lights on Top Gear/Fifth gear - Old Navy
Missed the edit:-

www.car4play.com/forum/post/index.htm?v=e&t=2779&m=69074
Last edited by: Old Navy on Sun 11 Mar 12 at 21:24
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New Sun 11 Mar 12 21:29 
 Modulated lights on Top Gear/Fifth gear - Runfer D'Hills
I like Chris Evans' garage.
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New Sun 11 Mar 12 21:30 
 Modulated lights on Top Gear/Fifth gear - spamcan61
If it isn't that then my guess is that the lights are pulsed at a high frequency by the car electronics, which is mixing/'beating' with the scan rate of the camera to produce a low frequency strobing effect.
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New Sun 11 Mar 12 21:37 
 Modulated lights on Top Gear/Fifth gear - Badwolf
Most modern buses have LED front destination screens. These rarely show up fully on photos, probably for the same reasons.
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New Sun 11 Mar 12 22:47 
 Modulated lights on Top Gear/Fifth gear - Dave_
>> Most modern buses have LED front destination screens.
>> These rarely show up fully on photos,
>> probably for the same reasons.

Likewise matrix signs on motorways and main roads.

LEDs are illuminated briefly several dozen times a second, the exposure time of a digital camera is too short to capture a whole light/dark cycle so there's a fair chance an LED will be unlit in any given frame.
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New Sun 11 Mar 12 21:59 
 Modulated lights on Top Gear/Fifth gear - AnotherJohnH
>> If it isn't that then my guess is that the lights are pulsed at a
>> high frequency by the car electronics, which is mixing/'beating' with the scan rate of the
>> camera to produce a low frequency strobing effect.
>>

+1
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New Mon 12 Mar 12 01:28 
 Modulated lights on Top Gear/Fifth gear - VxFan
Cameras can play funny tricks on the eye.

eg how does this helicopter fly with stationary blades?

www.clipaday.com/videos/how-can-this-helicopter-fly

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New Mon 12 Mar 12 09:30 
 Modulated lights on Top Gear/Fifth gear - AnotherJohnH
>> Cameras can play funny tricks on the eye.
>>
>> eg how does this helicopter fly with stationary blades?
>>


The interesting bit is not that they appear stationary, but that they are stationary for the whole display.

The rotor speed appears to be managed/maintained at a given value which is a multiple, or blade number related fraction, of the shutter speed regardless of the load.
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New Mon 12 Mar 12 06:09 
 Modulated lights on Top Gear/Fifth gear - Biggles
I was on the Autobahn the other day behind a BMW 5 series - under heavy braking the brake lights were flashing at about 3 Hz, presumably as a warning to those behind of the danger.
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New Mon 12 Mar 12 07:18 
 Modulated lights on Top Gear/Fifth gear - Zero
Under heavy braking some of the cars do indeed strobe the lights to catch visual attention, I have seen insignia's strobe alternate lights under heavy braking.

Mixed with this, the leds are actually switched in cycles - normally outside the visible frequency range, this is because the led is actually driven above its normal light output, but would burn out at that rate so its cycled on and off. I can see the frequency out of the corner of my eye


So given the above, its little wonder that video cameras with a frame rate of 30 fps and above, are well and trull flummoxed by LEDS,
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New Mon 12 Mar 12 07:33 
 Modulated lights on Top Gear/Fifth gear - R.P.
The X1's manual says it does that - doubt whether I'll ever know for sure though !
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New Mon 12 Mar 12 09:42 
 Modulated lights on Top Gear/Fifth gear - Bagpuss
Had to do an emergency stop in the 335d recently. I don't whether it strobed the brake lights, but it switched on the hazard flashers, which alarmed me as I wasn't expecting it.
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New Mon 12 Mar 12 10:40 
 Modulated lights on Top Gear/Fifth gear - VxFan
>> Under heavy braking some of the cars do indeed strobe the lights

Yep, my Vectra does that.

>> Had to do an emergency stop in the 335d recently - it switched on the hazard flashers,

The works Transit Connect does that. A little bit too eagerly IMHO. Even under what I would consider not heavy braking it can also happen.
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New Mon 12 Mar 12 11:13 
 Modulated lights on Top Gear/Fifth gear - Kithmo
>> >> Under heavy braking some of the cars do indeed strobe the lights
>>
My Prius does it too, although I can't think of any instance where I would be going fast enough for heavy braking LOL.
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New Mon 12 Mar 12 13:18 
 Modulated lights on Top Gear/Fifth gear - IJWS14
The Corsa we sold 3 years ago did this under heavy braking - supposed to make them more visible to those following
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New Mon 12 Mar 12 13:46 
 Modulated lights on Top Gear/Fifth gear - Old Navy
A bit like the annoying flashing cycle lights and too bright DRLs, if they are annoying they are doing their job. :-)
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New Mon 12 Mar 12 21:52 
 Modulated lights on Top Gear/Fifth gear - Dave_
My 53 plate 406 had a primitive version of EBA (emergency brake assist) and the hazard lights would come on when it was activated in a full-on emergency stop. Don't know if the Mondeo does the same because I pay for the tyres, brake pads, springs and bushes :)

Several years ago I saw an early, brand new BMW Z4 M being hooned around town one evening. It appeared to have more than one pair of brake lights in the rear clusters, with the extra bulbs being lit under heavier braking.
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