Could my flashing front lights cause....

[DJ]

an epileptic fit???

I thought of this today as I stopped to help some guy who had collapsed by the side of the road, turns out he had had some kind of fit, I called the ambulance and waited for it to come but didn't wait around once it had arrived, as I had to get on with my business.

However it did get me thinking about the afore mentioned question, I am always hearing these warnings on the TV about reports in the news which contain flash photography, just wondered if the same could apply to cyclists lights??

DJ

 

[Arch]

I think, although I'm not certain, that there's a certain frequency of strobing that's dangerous, and that bike lights don't achieve it.

 

[Norm]

I think, although I'm not certain, that there's a certain frequency of strobing that's dangerous, and that bike lights don't achieve it.

Sufferers of Photosensitive Epilepsy (for those who want to Google) can be triggered by flashing lights, or by light patterns, but only around 5% of those suffering epilepsy are photosensitive.

Most are triggered by a frequency of around 20Hz (flashing 20 times a second) which is way faster than any bike lights. However, some are triggered, apparently, by rates as low as 3Hz, which is not that much faster than some lights.

 

[thomas]

When I got in this evening I could still feel that my knog was flashing, even though my helmet was off and it wasn't on.

Not really relevant but, hey ho.

 

[Arch]

When I got in this evening I could still feel that my knog was flashing, even though my helmet was off and it wasn't on.

Not really relevant but, hey ho.

I think that's just a sort of visual memory, is it called 'persistance of vision'?

I get something similar when I watch the opening titles of Eastenders - which is an image of London that pans out and spins slowly. When it stops, I always get the impression it's turning back the other way, even though it's quite still.

 

[Cubist]

I think that's just a sort of visual memory, is it called 'persistance of vision'?

I get something similar when I watch the opening titles of Eastenders - which is an image of London that pans out and spins slowly. When it stops, I always get the impression it's turning back the other way, even though it's quite still.

'shrooms growing again now we've had a bit of rain?

 

[downfader]

More worrying is the percistance of the myth that cycle lights (and car indicators too for that matter) CAUSE epilepsy. I have heard several people, read one or two letters in the press and seen a few petitions all moaning that they "dont want to be made epileptic by your damn lights"

As I often say.. some people need screening

 

[classic33]

Got asked the same thing about the strobe effect caused by the sun, low on the horizon & cycling past a row of trees. Followed through to its conclusion & you could have the same effect from passing vehicles with their lights on & the person stationary. Same effect.

The frequency of the flash differs for everyone who suffers from that type of epilepsy.

The reason it appears on TV so much is, I feel, down to the blame some-one else for what happenned. So if your warned about it before hand & continue to watch it is done despite the warning being given.

Annoying that this is still doing the rounds, but it does show how little is known about it, epilepsy.

Working with computers I was constantly being asked if I was okay. In my case both cause & trigger are unknown.

 

[yenrod]

When I got in this evening I could still feel that my knog was flashing, even though my helmet was off and it wasn't on.

Not really relevant but, hey ho.

Everytime I put the bike away in the shed I feel as though I'm in a rave as the sparx-lights as seriously bad man !

 

[Arch]

'shrooms growing again now we've had a bit of rain?

No, really, try it (you can turn off straight away afterwards if you object to Eastenders). Try and look at the centre of the screen as the scene revolves outwards, and then keep staring when it stops. The middle bit seems to turn back...

Unless it is only me...

 

[mr_cellophane]

When I got in this evening I could still feel that my knog was flashing, even though my helmet was off and it wasn't on.

Not really relevant but, hey ho.

Those upside down letters back again.

 

[fossyant]

No, really, try it (you can turn off straight away afterwards if you object to Eastenders). Try and look at the centre of the screen as the scene revolves outwards, and then keep staring when it stops. The middle bit seems to turn back...

Unless it is only me...

Happens on a 50/60hz screen....... try a 100hz.... (not TFT - old school tubes)....I can't stand the old screens ...age.....honest..... - happy with my 100hz

 

[DJ]

No, really, try it (you can turn off straight away afterwards if you object to Eastenders). Try and look at the centre of the screen as the scene revolves outwards, and then keep staring when it stops. The middle bit seems to turn back...

Unless it is only me...

Is that the same effect as when I see the wheels on John Waynes wagon going the opposite way to the way they should be going? Especially when there is a whole tribe of Apache's after him the effect is amazing!!

 

[ufkacbln]

What is not generally known is that photo-epilepsy is trigered by a very narrow range of frequencies (16 - 25 Hz), outside the frequency of most bike ligths. According to the British Epilepsy association :

Flashing bicycle lights

There have been cases where red flashing lights (red light emitting diodes) on the back of bicycles have triggered seizures in people with photosensitive epilepsy, when they have been close to the lights as they were setting them up. If you have photosensitive epilepsy you may wish to avoid being close to these types of lights.

 

[Arch]

Is that the same effect as when I see the wheels on John Waynes wagon going the opposite way to the way they should be going? Especially when there is a whole tribe of Apache's after him the effect is amazing!!

No, I think that's something to do with the relative speed of rotation of the wheel and the speed at which the frames of film run through the camera - if the wheel spins faster than the film goes through, then it looks like it's going backwards. That's why wheels sometimes seem to spin one way and then the other, if they change speed slightly and go from being relatively faster to slower or vice versa.

It is a bit mind bending!

Persistence of vision is why you can see writing done with a sparkler, or why animation works.