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+--- Thread: Can this be done with the Xenon DRL's (/Thread-Can-this-be-done-with-the-Xenon-DRL-s)
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RE: Can this be done with the Xenon DRL's - Ezandania - 30-10-2011 07:40pm
Quattroman, i watched the vids you posted, but it seems like the White Dynamic DRL's seems to do those fancy flickers whilst the black Prestige DRL's manage to remain the same....so i'm guessing that rules out the framerate explanation? What do you think fisha?
RE: Can this be done with the Xenon DRL's - fisha - 30-10-2011 09:02pm
Both effects are a result of the shutter speed -v- flicker rate.
Different light conditions will generate different shutter speeds ... in the second vid, the pulses of LED's are closer in phase to the shutter speed. In fact its actually a very good example of rolling shutter effect of the camera.
The best thing I can liken it to is to imagine 2 amber flashing beacons like you get on recovery trucks. If they flash at a similar rate, then you'll notice that they go in sync and flash together, then slowly flash a different times until they reach a point where they flash alternatively, then they slowly go back to flashing together in sync again.
Its the same type of phasing between the flashes of the LED's and the opening of the shutter on the camera, they go in phase ( see the LED on ) then out of phase ( see LED off )
In the 2nd vid, you can see that sort of this happening with the LEDs as the ON portion scrolls downwards.
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Actually, just been watching the vid again ... simple explanation for the white versus black.
Modern cars have daytime driving lights ... those bright white LEDS. They are really bright when the main lights are off .... but they dim when the main lights are swtiched on.
When on brightly, they will be constantly on and dimming will be done by PWM ( pulse width modulation ) ... pulsing the LED's on and off - creating the shutter effect when viewed by the camera.
Looking at the vid ... black has main lights off, white has main lights on. Black LED's constantly on ( no pulsing effect ). White is pulsing the lights ( creating the effect )
RE: Can this be done with the Xenon DRL's - XFullFatTim - 31-10-2011 11:33am
Similar effect to wheels apparrently running backwards on films
RE: Can this be done with the Xenon DRL's - VirtualCamper - 26-02-2012 10:27pm
I saw the same effect on a car on Top Gear last Sunday, not a Land Rover, but some super car, thought that they might have made a comment about it but they didn't.
agree, its camera shutter/TV refresh rate/LED super fast flash rate
RE: Can this be done with the Xenon DRL's - PhilSkill - 26-02-2012 11:40pm
"Some supercar" sums up Top gear most of the time, "Here's an extra black version of the black edition Mercedes which has some extra black bits fitted and replaces the previous dark black edition, has some stupid horsepower that only costs a zillion pounds and is completely unusable as a car, but here it is eating it's tyres on a crappy disused English airstrip". Don't get me wrong it's sometimes quite entertaining and some of their road trips can be fun, if overly contrived, but time they got some new ideas!
RE: Can this be done with the Xenon DRL's - mark_n - 04-03-2012 11:53am
It's an effect called aliasing where the image is being sampled at one frequency and the image is being created at another. You then see a strobing effect equal to the difference in frequencies.
Any system which uses discrete samples like this will display the effect. In digital photography, sensors have an anti-aliasing filter over them to take the lens resolution down to what the sensor can handle without introducing aliasing or moire fringing.
In digital audio, a filter has to be used to remove the highest frequency sounds to keep them below the Nyquist frequency which is half the sampling frequency.
You also see strange optical effects when one mesh is passing behind another, such as on a motorway gantry.
RE: Can this be done with the Xenon DRL's - XFullFatTim - 04-03-2012 01:34pm
It is for this reason that often the continuity announcer will issue a health warning that there are flashing lights in the show before the transmission starts - it can set of epileptic fits in those liable to them.