# Can flashing lights cause epileptic fits?



## Rohloff_Brompton_Rider (13 Jan 2013)

On my ride last night, a pedestrian complained my lights "were not very good for epileptics", he was a young lad about eighteen at a guess and didn't appear to be being nasty, more off concerned tone of voice.


On the front I have a smart light 35 watt in flashing mode and a maglite xl200 which has a vey rapid and bright-ish flash mode.

Has he got a point? Can I unintentionally cause someone to have a fit?


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## ufkacbln (13 Jan 2013)

Photo-epilepsy is triggered by brightness and speed.

The British Epilepsy Association, the Epilepsy Alliance, and Epilepsy Action concur and have stated:



> *Red flashing bicycle lights*
> 
> Red flashing bicycle lights (light emitting diodes, or LEDS) have triggered seizures in a small number of people. This has happened when they were very close to the lights, setting them up.


 
The flash rate is outside the trigger threshold, however factual evidence is not always accepted in such emotive subjects

Other groups list bicycle lights as "potential" triggers.

The Brighton experience is typical. Note the use or the words "could", "expressed concern" as opposed to "have"



> *Lights on bikes make us have fits, say Brighton and Hove epileptics*
> 
> 2:40pm Thursday 28th January 2010
> *Cyclists are being urged to stop using fast-flashing bike lights over fears they could trigger epileptic fits. *
> ...


 
Basically if you have standard lights then there is no proven link or recorded incident in normal use with the triggering of epileptic fits.


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## shouldbeinbed (13 Jan 2013)

you never know but as they're pretty ubiquitous, you zip past people pretty quickly so aren't exposing them to it for long and as there aren't people falling down on the pavements in any great number I wouldn;t worry too much.

I guess the ones built to a national standard (so rule out the chinese cheapies) have to have some sort of checks done to avoid the usual trigger frequency for epileptic attacks.

My fenix-alike Dealextreme import torch does have a freaky and very fast random flash mode that I would be concerned about setting off near someone with epilepsy though. I never inflict that particular mode on the general public because it is painful to look at for someone not usually bothered by flashy lights..


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## Biker Joe (13 Jan 2013)

Possibly as some flashing bike lights are very bright.
On the other hand, if I was so afflicted, and a flashing light was coming towards me I would avert my eyes or close them until the danger was past.
Good question.


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## Rohloff_Brompton_Rider (13 Jan 2013)

Biker Joe said:


> Possibly as some flashing bike lights are very bright.
> On the other hand, if I was so afflicted, and a flashing light was coming towards me I would avert my eyes or close them until the danger was past.
> Good question.


Hehehe....they'd have to shut them for twenty minutes because of the slow speed I climb the hill upto sharneyford....


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## ColinJ (13 Jan 2013)

I have a front light with two flash modes. One mode slowly flashes SOS in Morse. The other mode flashes the light so fast that it does me in, and AFAIK I don't even suffer from epilepsy!

My stepdaughter suffered minor epileptic episodes when she was young where she'd go 'vacant' for no apparent reason. Tests with a flashing light showed that these episodes were not difficult to trigger. She seems to have grown out of the problem now.


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## machew (13 Jan 2013)

If her indoors is due for a seizure then the flashing lights from my bike can trigger one.


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## Rohloff_Brompton_Rider (13 Jan 2013)

Oh dear, I don't want to be the cause of someone's distress, I'll put my lights on solid and recharge daily.


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## ColinJ (13 Jan 2013)

bromptonfb said:


> Oh dear, I don't want to be the cause of someone's distress, I'll put my lights on solid and recharge daily.


I think having a lower-power flashing light on as well as the main one could still be eye-catching, but be unlikely to cause problems. Wouldn't help with battery life, of course.


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## Kookas (13 Jan 2013)

There are plenty of LED lights on the backs of pricey German cars and even in traffic lights, and although they flash much, much faster (to the point that they appear to be solid) and are much brighter than (most) bike lights I don't read too many complaints about those.


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## Drago (13 Jan 2013)

Photosensitive epilepsy is massively bigged up, mainly thanks to a scene in The Andromeda Strain where a scientist has a fit because of a flashing red emergency light.

Only 3% of those with epilepsy have this form, and the majority of those are sensitive in the 16-25hz region, which is very fast. Flashing strip lights, tv's, bike lights etc are simply not capable of triggering such an episode. There is some variance outside this threshold but its very, very rare. What the British Epilieptic Association claim about bike lights is not backed up be any science. I know all this because my youngest niece suffers.


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## Little yellow Brompton (13 Jan 2013)

bromptonfb said:


> On my ride last night, a pedestrian complained my lights "were not very good for epileptics", he was a young lad about eighteen at a guess and didn't appear to be being nasty, more off concerned tone of voice.
> 
> 
> On the front I have a smart light 35 watt in flashing mode and a maglite xl200 which has a vey rapid and bright-ish flash mode.
> ...


He doesn't , very much like the "flash photography" warning, it's misplaced concern by third parties, the flash rate is no where near high enough, and the contrast is not strong enough.


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## gaz (13 Jan 2013)

I've seen a few bike lights which flash at faster than 10hz and they are flipping annoying. Anything more than 4Hz is overkill.


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## antnee (13 Jan 2013)

As an old epileptic I can safely say that If I went to a disco I would perhaps fit. But as most of the flashing lights on bikes are nowhere near as bright as in a Disco I can't myself say that it does affect me, but then perhaps I'm not as epileptic as some other people are as it is an affliction of different degrees.


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## geo (13 Jan 2013)

Can understand your concern,however in my opinion flashing lights are the best way to get me noticed and hence keep me as safe as possible on the bike. So I will continue in flashing mode, as has been stated if your affected dont look at them.


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## Drago (13 Jan 2013)

The HSE no longer allow flashing lights in 'Discos' beyond 4hz, so you won't fit. Similar rules govern TV and flashing stuff and OFCUM enforce that.

In my nieces case it's sunlight shining through trees and railings etc while travelling in the car that trigger hers. At first my bro in law fitted blinds to the car but now she had tablets that eliminate it entirely. The drugs to control this form of epilepsy are supposed to be superb, almost universally effective.


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## machew (13 Jan 2013)

She must have a rare form then, the following have set off a fit
Advertising hoardings for 888.com at the football ground
Flashing lights at a rock festival 
And the best one, the blue lights on the ambo that came to pick her up (she had stopped fitting for about 10 mins before they came, put started again a few moments after they turned up)


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## ColinJ (13 Jan 2013)

Drago said:


> The HSE no longer allow flashing lights in 'Discos' beyond 4hz, so you won't fit. Similar rules govern TV and flashing stuff and OFCUM enforce that.
> 
> In my nieces case it's sunlight shining through trees and railings etc while travelling in the car that trigger hers. At first my bro in law fitted blinds to the car but now she had tablets that eliminate it entirely. The drugs to control this form of epilepsy are supposed to be superb, almost universally effective.


I don't know what frequency my bike light flashes at but it is bang in the middle of the range which I find annoying. It is fast enough to be disturbing, but not fast enough to appear continuously on.

I used to feel bad when zapped by disco strobe lights, and I also suffer from the sunlight-through-trees/railings problem. 

I don't have seizures, but I really don't like exposure to rapidly-flashing bright lights.

I am very sensitive to light levels and I suffer from SAD. On summer days with dark broken clouds blowing over it feels like someone is messing with my head - depressed-cheerful-depressed-cheerful ...


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## Grizzly (13 Jan 2013)

I've never known anyone to complain about the flashing lights on emergency vehicles and they are brighter and faster than bike lights.


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## HLaB (13 Jan 2013)

antnee said:


> As an old epileptic I can safely say that If I went to a disco I would perhaps fit. But as most of the flashing lights on bikes are nowhere near as bright as in a Disco I can't myself say that it does affect me, but then perhaps I'm not as epileptic as some other people are as it is an affliction of different degrees.


I'm an old epileptic too and I stayed away for years from things like disco but tbh all it served to do was make me miss out on my teen/early 20's years and when I eventually went to one I wished I had earlier.


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## TonyEnjoyD (13 Jan 2013)

To trigger photo-sensitive epilepsy, there has to be a specific set of curcumstances, and flashing bike lights are variable dances and often in amongst other light sources and at varied angles.
Also, you can also check the flash frequency as it may already be deigned at a rate known not to cause PS epilepsy

"A flashing strobe (or a close combination of multiple strobes sequenced together) must not be programmed to flash in the 5 Hz to 70 Hz frequency range.
Slower flash rates, and randomly flashing lights are not known to be a cause of photosensitive epilepsy.
Point sources of light are much less likely to induce seizures than a diffuse source of light which covers a large part of a person's field of vision.
To induce a seizure the light must be present in the center of the field of vision as opposed to the periphery.
Reducing brightness or increasing distance between a photosensitive viewer and the light source is effective for preventing photosensitive epileptic seizures.
Lights flashing in the distance, even in the frequency range of concern, are not known to cause seizures when in the presence of other lights of a more natural or chaotic nature"

I'm keeping mine operational


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## Rohloff_Brompton_Rider (13 Jan 2013)

As I said in my op my maglite flashes brightly and very very quickly, eye catching for motorists.....not so healthy for epileptic people. 

It is something I can change without a lot of effort, therefore I will.


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## classic33 (13 Jan 2013)

Drago said:


> Photosensitive epilepsy is massively bigged up, mainly thanks to a scene in The Andromeda Strain where a scientist has a fit because of a flashing red emergency light.
> 
> Only 3% of those with epilepsy have this form, and the majority of those are sensitive in the 16-25hz region, which is very fast. Flashing strip lights, tv's, bike lights etc are simply not capable of triggering such an episode. There is some variance outside this threshold but its very, very rare. *What the British Epilieptic Association claim about bike lights is not backed up be any science.* I know all this because my youngest niece suffers.


 So now you know more than the very people researching the condition! Research that has been done freee over many years, by many people.
We are free to say what we want, within reason.

IF the condition is "massively bigged up" it isn't due soley to a scene from one movie from 1971. Its only within the last 10 years that the warnings have been given about flash photography/flashing images. I don't know why, but it annoys the hell out of me when its used as a reason for not allowing me to do something.
I worked in an office enviroment where if I sat still for longer than a few seconds, someone would be sent to check on me to see if I was ok.

Ignorance it seems is king in situations like this. I use flashing lights, front & rear & I've followed vehicles with flashing lights with no ill effects. Think about indicators on motor vehicles, how often is a person going to come across those. I know their use is falling out of favour, but some people still use them.


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## machew (13 Jan 2013)

"Dennō Senshi Porygon" was a cartoon that caused seizures in 685 viewers that required a hospital visit. And about 12,000 viewers had a seizure type episode. This was from a clip that had strobes in about 12 Hz for about four to six seconds (wiki link)


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## Nebulous (14 Jan 2013)

A lot of very categoric statements here. While much of it could well be applicable to individuals, or small groups of people, it certainly isn't to everyone. Epilepsy can be very individual.

Just to pick up on some things. TVs certainly cause a problem for some people, as can computer screens and fluorescent lights for that matter. With computers bumping up the refresh rate can help and modern graphics cards are usually ok with that. Older ones weren't. There's some variation in TVs now with fancy ones often being at 100hz or even 200hz but older ones were all at 50. If people do have a problem then as was said earlier how much of your field of vision it fills is important so placing chairs at the opposite side of the room may help, as could having a smaller TV. When you come into DVDs/ bluray players it all changes again. My bluray player is at a cinema standard 24 hertz while dvds were almost all at 25. So it's quite feasible that some people could watch TV but not DVD/ blurays.

The problem with the unusual or different, like a strange random flash mode, is that people often don't know it is a problem for them until it strikes. With flashing lights it maybe a first seizure, so people could well be driving for instance when they are affected.

My Cateye back-up flash is quite a slow flash and I use my main light on solid. I think its very unlikely my cateye would affect anyone. My rear light on my roadbike has two flash modes and I generally put it on the slow one. It's also not very high powered. I'd be very wary about using a high powered led on a quick flash.


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## siadwell (14 Jan 2013)

If you read the descriptions of some of these cheap torches used as bike lights, the flashing mode is described as a fast strobe mode and is designed to disorientate an attacker. The crenelated bezel on some of these torches is also described as an "assault crown", leaving you in no doubt as to their defensive intentions. Basically, I wouldn't use such a fast flash on the road, no matter how eye-catching.


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## Globalti (14 Jan 2013)

I'm going to wear flashing lights when I go skiing next week and I think every other skier ought to as well.


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## sabian92 (14 Jan 2013)

It CAN trigger fits but most epileptics aren't light sensitive, contrary to popular belief. Most are stress induced, and lights don't bother them. My dad is an epileptic and can drive, watch TV, use a PC and everything in between and has only had a fit when stressed, and the last one was over 4 years ago.


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## snailracer (14 Jan 2013)

The British Standard for bike lights specifies that their flash rate shall be between 1 and 4 times per second.


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## Night Train (14 Jan 2013)

Kookas said:


> There are plenty of LED lights on the backs of pricey German cars and even in traffic lights, and although they flash much, much faster (to the point that they appear to be solid) and are much brighter than (most) bike lights I don't read too many complaints about those.


Those lights make me nauseous. They are fine if I am looking straight at them but, when driving, I am scanning the roads and the lights leave tracking dots of lights across my vision. I don't like them at all.


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## Crankarm (15 Jan 2013)

bromptonfb said:


> On my ride last night, a pedestrian complained my lights "were not very good for epileptics", he was a young lad about eighteen at a guess and didn't appear to be being nasty, more off concerned tone of voice.
> 
> 
> On the front I have a smart light 35 watt in flashing mode and a maglite xl200 which has a vey rapid and bright-ish flash mode.
> ...


 
I got annoyed with some t055er this evening who had an ultra bright rear light on flashing as he rode along teh GBW. Totally pointless and un-necessary. I was told to "F**k off!" when I told him to turn it off flashing mode.


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## Crankarm (15 Jan 2013)

Biker Joe said:


> Possibly as some flashing bike lights are very bright.
> On the other hand, if I was so afflicted, and a flashing light was coming towards me I would avert my eyes or close them until the danger was past.
> Good question.


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## Crankarm (15 Jan 2013)

geo said:


> Can understand your concern,however in my opinion flashing lights are the best way to get me noticed and hence keep me as safe as possible on the bike. So I will continue in flashing mode, as has been stated if your affected dont look at them.


 
They are a bl00dy menace and should be banned. There is no need for them. The RVLR which is the primary legislation describe a "constant " front light. No mention of flashing what so ever. Half the time it is off so totally illegal. How about if I could set the headlights of my car to flashing see how you like being blinded? For people like you who insist on riding on the GBW with flashing lights through the darkness as there is no motorised traffic to deal and you causing dazzling to all those who have the misfortune to approach you I reserve the full power of both my Max D lights aimed at you and when driving my main beam headlights.


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## geo (15 Jan 2013)

Crankarm said:


> They are a bl00dy menace and should be banned. There is no need for them. The RVLR which is the primary legislation describe a "constant " front light. No mention of flashing what so ever. Half the time it is off so totally illegal. How about if I could set the headlights of my car to flashing see how you like being blinded? For people like you who insist on riding on the GBW with flashing lights through the darkness as there is no motorised traffic to deal and you causing dazzling to all those who have the misfortune to approach you I reserve the full power of both my Max D lights aimed at you and when driving my main beam headlights.


 
Each to there own mate, but as Ive not been knocked off (yet ) I'll stick with flashing mode thank you. !!!

Not sure what you mean GBW ?? and as for there being no motorised traffic, where I ride, I think you will find the busy roads of Liverpool and surrounding areas have a considerable amount of motorised traffic.
To compare it to car headlights is rediculous, and you know it !!!


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## dodgy (22 Nov 2014)

Someone in the local town tried to pull me over today as "your light could cause an epileptic fit".

She was driving a Range Rover V8 in white. I guess she spends quite a lot of time worrying about the welfare of other people.


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## Flick of the Elbow (22 Nov 2014)

The biggest problem with flashing front lights are on cycle paths, little or no street lighting, the blindingly high intensity flashing coming at you head on. At times I've been totally unable to see where I'm going and have had to stop, always doing so at an angle so as to block the progress of the culprit.


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## blazed (22 Nov 2014)

bromptonfb said:


> On my ride last night, a pedestrian complained my lights "were not very good for epileptics", he was a young lad about eighteen at a guess and didn't appear to be being nasty, more off concerned tone of voice.
> 
> 
> On the front I have a smart light 35 watt in flashing mode and a maglite xl200 which has a vey rapid and bright-ish flash mode.
> ...


Two flashing lights on the front? One is bad enough cannot see why you would need two. 

Flashing front lights are irritating and distracting. People saying about emergency vehicles is very different as bike lights are so small the light is a lot more concentrated.


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## Racing roadkill (22 Nov 2014)

4Hz that's the key. If you flash a light at 4Hz you will induce a fit.


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## classic33 (22 Nov 2014)

Racing roadkill said:


> 4Hz that's the key. If you flash a light at 4Hz you will induce a fit.


No! See https://www.epilepsy.org.uk/info/photosensitive-epilepsy#about-hertz

_"Most people with photosensitive epilepsy are sensitive to 16-25 Hz. Some people may be sensitive to rates as low as 3 Hz and as high as 60 Hz."_


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## Racing roadkill (22 Nov 2014)

classic33 said:


> No! See https://www.epilepsy.org.uk/info/photosensitive-epilepsy#about-hertz
> 
> _"Most people with photosensitive epilepsy are sensitive to 16-25 Hz. Some people may be sensitive to rates as low as 3 Hz and as high as 60 Hz."_


 
I fecked someone up I used to work with, by flashing a blue green laser at 5 Hz. That was the first and last time he called me out on that point.


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## classic33 (22 Nov 2014)

Me, I just get fed up of people assuming they know what will cause a fit. I wish I knew, I'd then be able to avoid it


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## ufkacbln (22 Nov 2014)

Racing roadkill said:


> 4Hz that's the key. If you flash a light at 4Hz you will induce a fit.



Not according to the evidence...

It is a function of intensity and sequence, as above the range is wide and only an outlier would be affected at 4Hz



Racing roadkill said:


> I fecked someone up I used to work with, by flashing a blue green laser at 5 Hz. That was the first and last time he called me out on that point.



Intensity was probably the greater effect with a laser


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## dodgy (23 Nov 2014)

Are you permitted to drive if you suffer from epilepsy?


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## Racing roadkill (23 Nov 2014)

dodgy said:


> Are you permitted to drive if you suffer from epilepsy?



If you've suffered a fit in the last 12 months, then no.


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## Racing roadkill (23 Nov 2014)

All the bike lights I have, state that they comply with all lighting regs, including when in flashing mode. It does advise using constant mode in street lit areas, but there's nothing to stop you using flashing mode all the time, if you so wish.


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## Racing roadkill (23 Nov 2014)

Flick of the Elbow said:


> The biggest problem with flashing front lights are on cycle paths, little or no street lighting, the blindingly high intensity flashing coming at you head on. At times I've been totally unable to see where I'm going and have had to stop, always doing so at an angle so as to block the progress of the culprit.


The last time someone tried that trick on me, they lost the ensuing game of 'chicken'.


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## ufkacbln (23 Nov 2014)

Racing roadkill said:


> The last time someone tried that trick on me, they lost the ensuing game of 'chicken'.




With risks like that ...can I recommend that you wear a helmet as your risk is far higher than that of the average cyclist


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## theclaud (23 Nov 2014)

Cunobelin said:


> With risky like that ...can I recommend that you wear a helmet as your risk is far higher than that of the average cyclist


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## ufkacbln (23 Nov 2014)

Racing roadkill said:


> If you've suffered a fit in the last 12 months, then no.



The blanket 12 month ban is unfortunately a self perpetuating myth

There are a whole range of restrictions and differing periods. Can be as little as 6 months or no restrictions at all:

Isolated seizure:



> If you have a seizure after being seizure free for at least five years, the driving agency may consider this to be an isolated seizure.
> 
> This can only apply on one occasion.
> 
> ...



You can also hold a licence whilst experiencing fits if your seizures are "Asleep only", or in some other defined cases



> They have only had seizures while they sleep
> They have only had seizures that do not affect their consciousness
> Their doctor changed their dosage or medication, but they have now gone back to the original dosage or medication.



You may also have to stop for a period of time if your medication changes and the medical advice is that there may be a fit during the interim period


For a detailed look try Epilepsy Action who have a lot of informed and accurate information on these subjects


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## the_mikey (23 Nov 2014)

Many modern lighting systems flash to some degree, an LED flashing at 30Hz will look like a constant light until it's moving past you and some speed, the reason for this is it's easier and more efficient to turn an LED on and off with different mark-space ratios to control the apparent brightness than it is to control the current to the LED as this generates more heat than the typical pcb mounted resistor can handle before burning out.

It's particularly noticeable on cars with LED lighting systems.


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## ufkacbln (23 Nov 2014)

the_mikey said:


> Many modern lighting systems flash to some degree, an LED flashing at 30Hz will look like a constant light until it's moving past you and some speed, the reason for this is it's easier and more efficient to turn an LED on and off with different mark-space ratios to control the apparent brightness than it is to control the current to the LED as this generates more heat than the typical pcb mounted resistor can handle before burning out.



In fact for the older ones amongst us, this was the reason that LEDs were not allowed

When the first "Vistalite" LED rear lights came out they were not acceptable because the LED was by definition flashing and therefore not compliant


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## brand (23 Nov 2014)

Racing roadkill said:


> If you've suffered a fit in the last 12 months, then no.


You must have two episodes before your classed as epileptic. If you have one you are not allowed to drive for 3 months. I am not sure if you have a one barred from driving as they have done some changes since I was barred 20 odd years ago.
To answer the OP my last reading was about 5% of eppys are effected by flickering lights. The flashing must be between 2 figures so many per minute. You would assume that the makers would take that into account. I would be surprised if they all do.
Computer don't flash television do but you had to be close enough to see it. They have now doubled the flicker rate so you cannot see it.


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## ColinJ (23 Nov 2014)

dodgy said:


> Are you permitted to drive if you suffer from epilepsy?


A stall holder on our local market suffered fits as a young man but medication stopped them so he had been driving ever since ....



Racing roadkill said:


> If you've suffered a fit in the last 12 months, then no.


The stall holder didn't turn up for a few weeks, and when he did he had a new assistant. The fits had suddenly returned as he had been driving back down the M62 in his van. The result was a multiple pile-up, fortunately not causing serious injuries or deaths! His licence has been taken away from him so his assistant is now the driver. He told me that whether he gets his licence back depends on whether his new medication turns out to be 100% effective in the long term.


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## brand (24 Nov 2014)

Kookas said:


> Computer screens do flash, usually at 60Hz.


Some disagreement on the net about this. Basically you have to be able to see the flash/flicker for it to have an effect.
https://www.epilepsy.org.uk/info/photosensitive-epilepsy/computer-television-screens


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## Kookas (24 Nov 2014)

brand said:


> Some disagreement on the net about this. Basically you have to be able to see the flash/flicker for it to have an effect.
> https://www.epilepsy.org.uk/info/photosensitive-epilepsy/computer-television-screens



Sorry, I Googled it and yeah, you're right, LCD pixels don't normally switch off between frames. Indeed, in this slow-mo video you can hardly see the change at all because the refresh overlaps the previous one.


View: http://youtu.be/DjMROqGSaOE

That said, I believe the same applies for LCD/LED TVs.


View: http://youtu.be/BBgFampjkPs


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## classic33 (24 Nov 2014)

Whats the flicker/flash speed of fluorescent lighting, especially the newer compact type bulbs.
Warned about the possibility of these triggering a fit.
You can't actually see it flash/flicker, but some do come with the warning about photosensitive epilepsy.


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## Flick of the Elbow (24 Nov 2014)

Racing roadkill said:


> The last time someone tried that trick on me, they lost the ensuing game of 'chicken'.


Sadly, such a selfish and aggressive attitude is typical of many who use flashing lights, they don't care about their effect on anyone else. They are the cycling equivalent of 4x4 drivers.


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## the_mikey (24 Nov 2014)

classic33 said:


> Whats the flicker/flash speed of fluorescent lighting, especially the newer compact type bulbs.
> Warned about the possibility of these triggering a fit.
> You can't actually see it flash/flicker, but some do come with the warning about photosensitive epilepsy.



I suspect at least 50Hz , but the phosphor coating has some persistence which masks any apparent flash or flicker.


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