Flash and Epilepsy?

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Broric

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Looking for some advice.

Was shooting this evening using a speedlight and apparently I set of someone's epilepsy sat across a (very large) square.

As soon as we were made aware we stopped and moved away but I wondered if anyone had experienced this before? I wasn't even aware it was possible but thinking about it, I was in HSS mode which I guess could in theory set someone off?

I've tried googling but not really come back with an answer. Obviously want to do whatever I can to avoid a similar issue in the future.

Cheers
 
I should qualify this by saying I'm not a doctor. But it seems very unlikely that you, on your own at a distance set off someone's photosensitive epilepsy. You normally need somewhere around 20 flashes a second to trigger it so a group of photographers and I guess its possible, but just one. Not so much.

I would guess that there was another trigger and you've been blamed. I'd bet there was another cause.

https://www.epilepsy.org.uk/info/photosensitive-epilepsy
 
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That's what I was thinking but didn't want to argue when it comes to someone's health, better to be safe, etc.

I wasn't sure how high sync speed would factor in, as I understand it, that fires lots of tiny fast flashes so thought that might be a possibility.
 
ecoleman said:
the folks on the news etc are always warning about flash photography so I guess it's possible.
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I always thought that was simply if you had a press pack of photographers then it seems possible to generate the right frequency of flashes to trigger seizures. I don't think 1 photographer on their own would manage 16-25 flashes a second. Even 3 flashes a second would be hard work.

HSS works at about 50 kHz so its way above what would trigger.
 
boyfalldown said:
I always thought that was simply if you had a press pack of photographers then it seems possible to generate the right frequency of flashes to trigger seizures. I don't think 1 photographer on their own would manage 16-25 flashes a second. Even 3 flashes a second would be hard work.

HSS works at about 50 kHz so its way above what would trigger.
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The Lencarta Superfast is capable of 20fps (other fast lights are available), getting a camera to fire it that fast is a different issue.
 
All sorts of factors can set of photosensitive epilepsy - even chequer patterned shirts can do it. The intensity of the light has very little to do with it, if it's visible it can set of an attack/episode. Hopefully the person whose seizure it possibly triggered is OK. IMO, you did the right thing in stopping - while I'm not epileptic myself, I have had friends who were; one of them could be triggered by being driven past vertical railings or along tree lined roads if he forgot to take his medication.
 
I am medically trained, and its seems unlikely that it was the cause ;) My first reaction was b*****ks, if he was that sensitive he would never go out. How did they know it was you and not a zillion other possible causes.

Nod hit it on the head, it was probably due to him not taking his meds or not getting the balance of medication correct.
 
Also medically trained. Seems very unlikely to me. Whilst I wouldn't attribute it to something the patient has necessarily done, there a&e numerous more likely explanations than the flash.
 
andyscott said:
I am medically trained, and its seems unlikely that it was the cause ;) My first reaction was b*****ks, if he was that sensitive he would never go out. How did they know it was you and not a zillion other possible causes.

Nod hit it on the head, it was probably due to him not taking his meds or not getting the balance of medication correct.
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Sir SR said:
Also medically trained. Seems very unlikely to me. Whilst I wouldn't attribute it to something the patient has necessarily done, there a&e numerous more likely explanations than the flash.
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Off topic rant...:D
How comes you're allowed to profess to being 'medically trained' and everyone takes your word for it. But when I say I worked for benefit fraud I get accused of 'forum bluff', 'willy waving' etc. Maybe I should have said I'd worked for MI6 or or was a legal expert or something. :thinking:

#justsayin #worldsgonemad
 
Statistically it works like this:

0.005% of the population have photosensitive epilepsy.

Of those the sensitive frequency range is generally 3-30Hz (ish)

The key is the speed, whilst a single flash is unlikely to set it off, two or three flashes in succession might.

The BBC thing is generally considered to be arse-covering flummery.

So whilst it is very rare, it can happen. HSS would be probably the most likely way to trigger it with a flash unit.

Nod's examples are good ones. It's not just light that sets it off - it is the changes in light; hence gaps in the railings whilst driving etc.
If an indirect flash alters the light level in an environment - that can act as a trigger!



#weirdthingspressphotographershavetolearn
 
Phil V said:
Off topic rant...:D
How comes you're allowed to profess to being 'medically trained' and everyone takes your word for it. But when I say I worked for benefit fraud I get accused of 'forum bluff', 'willy waving' etc. Maybe I should have said I'd worked for MI6 or or was a legal expert or something. :thinking:

#justsayin #worldsgonemad
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Somebody once taught me how to put a plaster on....that counts as medically trained, right? [emoji6]
 
DemiLion said:
The BBC thing is generally considered to be arse-covering flummery.
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By Ofcom - they mandate PSE checks in broadcasting licences. The fact their expert also manufactured the only test equipment is irrelevant.
 
Was the person actually photo sensitive or were you simply an easy hook to hang the attack on?

Lots of factors can trigger an attack, not simply flash.
 
Public space I guess?
Ask them to move on and continue shooting :)
 
DemiLion said:
Statistically it works like this:

0.005% of the population have photosensitive epilepsy.

Of those the sensitive frequency range is generally 3-30Hz (ish)

The key is the speed, whilst a single flash is unlikely to set it off, two or three flashes in succession might.

The BBC thing is generally considered to be arse-covering flummery.

So whilst it is very rare, it can happen. HSS would be probably the most likely way to trigger it with a flash unit.

Nod's examples are good ones. It's not just light that sets it off - it is the changes in light; hence gaps in the railings whilst driving etc.
If an indirect flash alters the light level in an environment - that can act as a trigger!



#weirdthingspressphotographershavetolearn
Click to expand...

The 'shutter speed' of the human eye is around 1/25sec or so. Anything flickering much faster than that appears as continuous light (eg movies, TV pictures). High Speed Sync pulses the flash extremely rapidly, many thousands of times per second, up to 40,000x according to Canon.
 
HoppyUK said:
The 'shutter speed' of the human eye is around 1/25sec or so. Anything flickering much faster than that appears as continuous light (eg movies, TV pictures). High Speed Sync pulses the flash extremely rapidly, many thousands of times per second, up to 40,000x according to Canon.
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A film set that I was lighting recently had a already troublesome neighbour come up and claim that our lighting had set off her husband's epilepsy. While we didn't call her out on it, our single light in the street was flagged off entirely from her house, and was a HMI that is safe and flickers at less than 1000hz....
 
Sir SR said:
Somebody once taught me how to put a plaster on....that counts as medically trained, right? [emoji6]
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I'm not sure that it does...

But as I know that you work as an anesthitist I'm guessing that that does count:)
 
My first thought before reading any replies was... you annoyed someone somehow with the flash and they said that to make you feel bad and stop..

read the replies and I still think the same..
 
HoppyUK said:
The 'shutter speed' of the human eye is around 1/25sec or so. Anything flickering much faster than that appears as continuous light (eg movies, TV pictures). High Speed Sync pulses the flash extremely rapidly, many thousands of times per second, up to 40,000x according to Canon.
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Sorry, but that was disproven in about 1911.

The continuous motion of TV is a learned response. http://www.bbc.co.uk/rd/blog/2013/12/high-frame-rate-at-the-ebu-uhdtv-voices-and-choices-workshop

EDIT: it was 1912:
The theory of persistence of vision is the belief that human perception of motion (brain centered) is the result of persistence of vision (eye centered). The theory was disproved in 1912 by Wertheimer but persists in many citations in many classic and modern film-theory texts.
 
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st599 said:
Sorry, but that was disproven in about 1911.

The continuous motion of TV is a learned response. http://www.bbc.co.uk/rd/blog/2013/12/high-frame-rate-at-the-ebu-uhdtv-voices-and-choices-workshop

EDIT: it was 1912:
The theory of persistence of vision is the belief that human perception of motion (brain centered) is the result of persistence of vision (eye centered). The theory was disproved in 1912 by Wertheimer but persists in many citations in many classic and modern film-theory texts.
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Interesting links, thank you. It's a complicated question, but 1/25sec or so is not a bad yardstick for practical purposes. The most significant difference is with peripheral vision where more rods are present on the retina, more sensitive to light/dark than colour, and can detect faster flicker rates. Epileptics may well be sensitive to this.

I have an epileptic work colleague, though he has no problem with flashing lights, or driving, whatever. But mild stress almost always sets him off, like giving a presentation. He just excuses himself, lies down flat with his wayward arm pressed against the wall, fits for maybe 30 seconds, then gets up as if nothing happened.
 
Garry Edwards said:
I'm not sure that it does...

But as I know that you work as an anesthitist I'm guessing that that does count:)
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That certainly means he knows ways of making them shut up! :sleep:
 
Broric said:
Looking for some advice.

Was shooting this evening using a speedlight and apparently I set of someone's epilepsy sat across a (very large) square.

As soon as we were made aware we stopped and moved away but I wondered if anyone had experienced this before? I wasn't even aware it was possible but thinking about it, I was in HSS mode which I guess could in theory set someone off?

I've tried googling but not really come back with an answer. Obviously want to do whatever I can to avoid a similar issue in the future.

Cheers
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If the square was large then that sounds unlikely but the oddest things can trigger attacks - and certainly did in my grandfather's case.
The flipside is that one of the best models I've ever worked with occasionally gets massive seizures that can wipe her out for days. Flashes never set her off.

I wouldn't do anything special to avoid the issue in future. It's a large public space and you're using a device which has passed all the relevant safety standards.
 
HoppyUK said:
Interesting links, thank you. It's a complicated question, but 1/25sec or so is not a bad yardstick for practical purposes. The most significant difference is with peripheral vision where more rods are present on the retina, more sensitive to light/dark than colour, and can detect faster flicker rates. Epileptics may well be sensitive to this.

I have an epileptic work colleague, though he has no problem with flashing lights, or driving, whatever. But mild stress almost always sets him off, like giving a presentation. He just excuses himself, lies down flat with his wayward arm pressed against the wall, fits for maybe 30 seconds, then gets up as if nothing happened.
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I really hope you mean being driven rather than driving, Richard!
 
Nod said:
I really hope you mean being driven rather than driving, Richard!
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I have epilepsy and I drive..

theres a heck of a lot of forms of epilepsy.. my attacks happen in sleep mode or just as i go to sleep.. soemhting not in sync... I had my driving licence taken away when it was diagnosed and when i got it back i had to have checks every 6 mths then every yr then every 3 yrs before i got it back fully... no problems during day so was ok
 
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HoppyUK said:
Interesting links, thank you. It's a complicated question, but 1/25sec or so is not a bad yardstick for practical purposes. The most significant difference is with peripheral vision where more rods are present on the retina, more sensitive to light/dark than colour, and can detect faster flicker rates. Epileptics may well be sensitive to this.

I have an epileptic work colleague, though he has no problem with flashing lights, or driving, whatever. But mild stress almost always sets him off, like giving a presentation. He just excuses himself, lies down flat with his wayward arm pressed against the wall, fits for maybe 30 seconds, then gets up as if nothing happened.
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Very strange to be fitting and getting up and carrying on as normal. My experience has been one of sheer exhaustion afterwards - a deep need for sleep. And if he's driving afterwards that's illegal. You have to be something like 6-12 mthd fit free before u can drive - can hardly remember it's been that long ago for me.

Anyway, none of us are neuro surgeons. We cannot guess whether it would affect people so the best approach is to respect the situation. I don't think anyone really wants to be the cause of someone fitting in the middle of a public place, quite possibly falling and harming themselves in the process. Broric did the responsible thing. Epilepsy can be difficult enough to live with dependent on its nature. I'm very lucky
 
KIPAX said:
I have epilepsy and I drive..

theres a heck of a lot of forms of epilepsy.. my attacks happen in sleep mode or just as i go to sleep.. soemhting not in sync... I had my driving licence taken away when it was diagnosed and when i got it back i had to have checks every 6 mths then every yr then every 3 yrs before i got it back fully... no problems during day so was ok
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Richard's colleague fits at work so waking fits.

Despite never having fitted, it took the DVLA the best part of 18 months to give me my license back after brain surgery because I had been prescribed (and taking) Phenytoin just in case the surgery had disturbed something.

As Julie said, the OP did the right thing.
 
I think @Sir SR works in A&E or something like that. Might be a porter, might be surgeon general! :p

I have shot portraits of someone with epilepsy. I knew this and asked him if anything we were doing would be a problem and he said no as he is on his meds and as long as I didn't do the hi-speed disco type continuous flashing he would be fine. I however did insist on discussing a procedure of what the flipping heck I would have to do should his epilepsy kick in. Just in case.

Have produced sets of corporate portraits with a few declaring a history of epilepsy however they said the infrequent flashes of my lencarta standard elitepro kit would not induce an attack.

So far no probs! Doubt your flashes ahd any influence on this guy.
 
Nod said:
Despite never having fitted, it took the DVLA the best part of 18 months to give me my license back after brain surgery because I had been prescribed (and taking) Phenytoin just in case the surgery had disturbed something.
.
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the bad thing for me was.. once on the dvla thing and although clear for 30+ yrs.. I am not allowed to put in for HGV which was something I wanted to do.. Did mc CPC and stuff working towards transport management but really always wanted to do HGV ..but seems couldnt even apply although full driving licence back with no checks needed..
 
N
Marcus Geezer said:
I think @Sir SR works in A&E or something like that. Might be a porter, might be surgeon general! :p

I have shot portraits of someone with epilepsy. I knew this and asked him if anything we were doing would be a problem and he said no as he is on his meds and as long as I didn't do the hi-speed disco type continuous flashing he would be fine. I however did insist on discussing a procedure of what the flipping heck I would have to do should his epilepsy kick in. Just in case.

Have produced sets of corporate portraits with a few declaring a history of epilepsy however they said the infrequent flashes of my lencarta standard elitepro kit would not induce an attack.

So far no probs! Doubt your flashes ahd any influence on this guy.
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Nah, he works in an operating theatre and people (not me) call him sir:) He doesn't cut people up, he just sends them to sleep so that other sirs can cut them up...
 
KIPAX said:
the bad thing for me was.. once on the dvla thing and although clear for 30+ yrs.. I am not allowed to put in for HGV which was something I wanted to do.. Did mc CPC and stuff working towards transport management but really always wanted to do HGV ..but seems couldnt even apply although full driving licence back with no checks needed..
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Royal PITA! Long may you remain clear.
 
I'm another qualified medic and photosensitive epilepsy is usually triggered (note the word usually) with strobing between 3 and 30 flashes a second (3-30 hertz) the film industry normally use 4 flashes a second as a guide in movies. In most cases it's a few seconds or longer of exposure to the flashing that triggers a seizure.
In a public place it's tricky, but the fact remains it's public, if they consider themself at risk by staying exposed to a possible source, then they should move themself to safety, after all it's their body thats at risk.
 
Is there any research relating susceptibility to the brightness of the flashing? I know the 3 - 30 Hz is quoted by Of com, but that's based on a TV screen. Would using a flashgun which is many 10s of times brighter increase the likelihood?
 
It's got nothing to do with OFCOM. The figures quoted are from research carried out behalf of Epilepsy Action.
 
I to have suffered clear now for 15 years my daughter also has it I had my driving licence she doeasnt stupid part of it is that anyone can have a fit triggered same as heart attack stroke etc at anytime if you have a heart attack they don't stop you driving I now understand the dvla waiting is now a year clear which to me is going back the opposite way abit too much as if your on medication and I think 2 years clear is a better idea
 
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