# Flicker Vertigo



## DanAyers

So, For anyone who doesn’t know, I hold a Master’s degree in Occupational Safety Management; which goes well with my Bachelors in Technical Theater and 20 years working in the industry. 

One of my professors from the safety program reached out to me this morning, after attending Trans Siberian Orchestra in Kansas City last night she experienced flicker vertigo from the lights moving and flickering too fast during the performance. I’m not terribly familiar with flicker vertigo, and I learned a few things about it from her today but I’m curious if people here are more knowledgeable than me and if it could spark a good discussion about what it is, and what LD’s need to look out for to prevent it. Personally, I’d like to understand it better, so I would love to hear stories, and any information anyone wants to share. 

I guess to start here’s a definition:




Flicker vertigo - Wikipedia





en.m.wikipedia.org





*Flicker vertigo*, sometimes called the *Bucha effect*, is "an imbalance in brain-cell activity caused by exposure to low-frequency flickering (or flashing) of a relatively bright light."[1] It is a disorientation-, vertigo-, and nausea-inducing effect of a strobe light flashing at 1 Hz to 20 Hz, approximately the frequency of human brainwaves.[2][3] The effects are similar to seizures caused by epilepsy (in particular photosensitive epilepsy), but are not restricted to people with histories of epilepsy.
This phenomenon has been observed during helicopter flight; a Dr. Bucha identified the phenomenon in the 1950s when called upon to investigate a series of similar and unexplained helicopter crashes. Flicker vertigo in a helicopter occurs when the pilot or front passenger looks up through the blades of the main rotor as it turns in the sun causing the light to strobe.

So what stories do you have?
Thanks
Dan


----------



## Robert

Dragon Ball Z and Pokemon both had TV broadcasts that caused seizures and illness in viewers for strobe effects.


----------



## TuckerD

Very interesting! This weekend I'll see if I can find any literature on it. Cool background (OSM) by the way. Probably not enough of that in the industry.


----------



## macsound

Seems like it would be an interesting phenomenon to look at because concert lighting is soooo flash and trash lately and stobe effects have become more convoluted with the advent of LED engines and designers creativity such as strobing through color, gobos and movements.


----------



## Jay Ashworth

On the epilepsy side, I gather that photosensitive epilepsy (which might also be Jacksonian) is triggered around 4-6Hz; not sure about the vertigo thing.


----------



## derekleffew

Same or different issue?







‘Star Wars’: Disney Warns Theaters of Flashing Light Sequences, Seizure Concerns for ‘Rise of Skywalker’

Disney has issued an uncommon warning to cinema owners around the globe asking them to notify customers that certain visuals and sustained flashing light sequences in ‘Star Wars: The Rise of …



www.hollywoodreporter.com


----------



## MNicolai

Probably similar triggers but unique causes. Epilepsy affects select individuals. Flicker vertigo messes with your visual perception of space, speed, and proximity; and can induce symptoms in any individual under the right circumstances.

It's like those really slow strobe effects in haunted houses. The deliberately long cycle between flashes messes with your ability to accurately perceive which direction something is headed, how quickly it is moving, and which was it up.


----------



## Malabaristo

MNicolai said:


> Flicker vertigo messes with your visual perception of space, speed, and proximity; and can induce symptoms in any individual under the right circumstances.



It would be interesting to see research on how true this is. What portion of the population is more or less susceptible to which kinds of flicker? If there are certain values that affect almost anyone, then it would be useful to have those as parameters when designing silly flashy things. My guess is that those levels would have to pretty extreme for an average person, but there's a smaller subset of people who are much more sensitive to some (all?) kinds of flicker. If everyone at the TSO concert had the same reaction as Dan's professor, then you'd think those shows would be less popular.


----------



## DanAyers

Malabaristo said:


> It would be interesting to see research on how true this is. What portion of the population is more or less susceptible to which kinds of flicker? If there are certain values that affect almost anyone, then it would be useful to have those as parameters when designing silly flashy things. My guess is that those levels would have to pretty extreme for an average person, but there's a smaller subset of people who are much more sensitive to some (all?) kinds of flicker. If everyone at the TSO concert had the same reaction as Dan's professor, then you'd think those shows would be less popular.



I want to clarify one word, I want to replace “True” with “widespread”.

I don’t think it is very widespread but for her it is “true” Interestingly enough she recognized it and she made a video of that part of the show with her phone specifically so she could ask me about it later. And it is flashy.

What would make for an interesting study would be to gather data and identify correlations.
What percentage of audience member exhibit mild symptoms that do not warrant medical care? How long? Is it the same part of the show; etc.


----------



## TimMc

Interesting topic, and one that my shop encountered last year.

We had a small arena show with a popular 1980's act who carries no LD but has a general plot and color media list in their rider. Our LD contacted the act and got a set list, downloaded the songs from youtube and built a show. LD also watched recent live performance vids to have an idea of what the band was accustomed to.

At sound check we are told by the tour manager that the light show needs to be re-done because a member of the rhythm section has vertigo-like episodes from flashing & panning lights. Really? We've been in direct contact with you, Mr TM, and you never mentioned this. We've been in contact with the production manager and he's not brought it up when asked if there were looks the band did NOT want used. The soap opera that followed did not include me directly, but the client specifies the "general" nature of the shows we do for them unless the act has a specific plot & LD (think: Styx - Love ya, Libby!) and we were reluctant to scrap the entire design. Ultimately our LD went in and edited each look to give the affected player a "hidey-hole" of space where no movers scanned across or up/down, turned the strobe cues into longer burns and did a couple other things. The result was acceptable to our client and the musician was not incapacitated on stage. Also no animals were harmed... 

But it's a real issue and some folks seem to be particularly susceptible to it and it could make a player's "day at the office" really suck. Ultimately we don't want anyone's day to suck so we'll find a way to de-suckify the offending issue.


----------



## CM Wardrobe

I know of a couple coworkers who experienced flicker vertigo symptoms when the theater that I work at did an upgrade to LED lights in the entire building. I'm not sure for stage lighting, but I know that there are areas of the building where the new LED lights do really flicker. I think that things that have been helpful are having the right fixture and the quality of the bulb.


----------



## Pyrotech

Working in the utility industry energy efficiency program, I would sometimes run into people who would complain of headaches caused by fluorescent lights. Most thought it was from the poor color quality and 'harshness' of the fluorescents, but most said the headaches were lessened when we upgraded them to the newer T8 lamp/electronic ballast combination (I was in the industry long enough ago for that to be the 'latest and greatest - pre-LED), which operate at 20,000 Hz rather than 60 Hz (or 50 Hz, for you non-continental US folks)


----------



## Jenn4art

DanAyers said:


> So, For anyone who doesn’t know, I hold a Master’s degree in Occupational Safety Management; which goes well with my Bachelors in Technical Theater and 20 years working in the industry.
> 
> One of my professors from the safety program reached out to me this morning, after attending Trans Siberian Orchestra in Kansas City last night she experienced flicker vertigo from the lights moving and flickering too fast during the performance. I’m not terribly familiar with flicker vertigo, and I learned a few things about it from her today but I’m curious if people here are more knowledgeable than me and if it could spark a good discussion about what it is, and what LD’s need to look out for to prevent it. Personally, I’d like to understand it better, so I would love to hear stories, and any information anyone wants to share.
> 
> I guess to start here’s a definition:
> 
> 
> 
> 
> Flicker vertigo - Wikipedia
> 
> 
> 
> 
> 
> en.m.wikipedia.org
> 
> 
> 
> 
> 
> *Flicker vertigo*, sometimes called the *Bucha effect*, is "an imbalance in brain-cell activity caused by exposure to low-frequency flickering (or flashing) of a relatively bright light."[1] It is a disorientation-, vertigo-, and nausea-inducing effect of a strobe light flashing at 1 Hz to 20 Hz, approximately the frequency of human brainwaves.[2][3] The effects are similar to seizures caused by epilepsy (in particular photosensitive epilepsy), but are not restricted to people with histories of epilepsy.
> This phenomenon has been observed during helicopter flight; a Dr. Bucha identified the phenomenon in the 1950s when called upon to investigate a series of similar and unexplained helicopter crashes. Flicker vertigo in a helicopter occurs when the pilot or front passenger looks up through the blades of the main rotor as it turns in the sun causing the light to strobe.
> 
> So what stories do you have?
> Thanks
> Dan


Hi Dan, 
I can't speak to the vertigo in visible flicker like you mentioned in this instance but in the last year I have discovered I have sensitivity to subsensory flicker between 100-400hz from LEDs. This is area lighting primarily in buildings and streetlights. But I work in live theater on wardrobe and now that LEDs are more prevalent in design I've had to stop going to see live productions from the audience perspective. LEDs not properly installed with drivers to compensate for AC power will flicker (in US) around 120hz. But since live productions typically use dimmers, and since LEDs don't dim, the dimmers are increasing the flicker in this range that I'm sensitive to. I have experienced migraine headaches, dizziness, stroboscopic effects, nausea and concussion like symptoms from these lights and the only way I can get rid of the headache is an experimental treatment dependent on office hours.


----------



## AlDenteUmber

I have extremely bad flicker vertigo which has gotten progressively worse as I get older. I have all of the "in extremely rare cases" symptoms like loss of muscle control and seizure, although sometimes I only have mild things like loss of fine motor control, becoming disoriented, and generally not feeling great depending on many factors. The list of things that bother me is so extensive that instead I'm just going to write out a list of things that are helpful to do or avoid, but I'm happy to answer more specific questions as best I can:

-avoid lights that scroll through the audience. The more of one's field of view a light affects the more likely it is to cause flicker vertigo. When the light change is directly on you, closing your eyes doesn't even help.
-avoid siren lights for long periods of time. Once we get the idea that the police/ambulance/fire truck are there, find a way to fade it out or have the driver turn them off when they get out of the car.
-make conservative assumptions about what might bother people and post flashing light warnings, ideally giving the maximum frequency of flash in the show. For me, anything that you would even consider flashing is good to know about in advance. Faster than 3hz will disorient me enough that I can't get out of the situation fast enough to avoid a seizure. I usually call ahead to ask nowadays. Adding some context of when to expect this if it is only once or twice can help sensitive folks be able to watch most of the show (ie. the twister in Wizard of Oz could be avoided while seeing the rest of the show)
-limit the amount of realistic fire on stage. Your flicker candles may be very pretty, but if there are 50 of them on stage for 2 hours I will not be able to watch the show.
-having "flicker free" night of a show would be really cool the same way there are low sensory nights (actually these would make sense to be the same night) and sign language nights.
-avoid using siren or flashing lights in your safety equipment wherever possible. 
-when making job posts, include information like if people will be expected to ride in a car to get to a storage location, etc and if strobe lights will be tested during the call


----------



## Lasermike

I’m not sure I’d say I have flicker vertigo but rapid flashing or panning lights and pulsing sounds make me very uncomfortable, sometimes to the point of nausea. Enough so I will stop the video if I can or close my eyes and turn away if it’s live.
Michael


----------



## Jay Ashworth

There's a fundamental question that's always danced around in trying to decide how to handle questions like this -- and they don't just pop up in theatre, of course:

To what degree do the 'needs' of the many outweigh the needs of the few... or the one.

I've worked in 2 theatres regularly since 2015 or so.

Both have Wagner 72MHz hearing-impaired systems, with 4-6 receivers a piece. The 184 seat municipal theatre, we did 5 shows a year, 15 performances each. The 246 seat college theatre... much more.

In *all of those shows*, I know of a total of 2 times a Wagner was checked out at the city hall, and we've *never* used them at the college at all, in the 10 years since its refit. I routine them at the beginning of every season anyway, and check them out before each run, for the same reason the guy who gives the lethal injection taps out the bubbles first: for *me*.

And I know that usage is higher in different places -- though the average age in that city hall audience for plays was dead..

But having or not having HIA doesn't affect the rest of the audience.

Keeping or cutting a loud gunshot or flashing lights is another story. (In one show I was asked to provide a rifle shot. NOBODY there was cognizant of just how much SPL that system could produce without popping a driver except me. )

So: if there's an element of a show which might have an effect on a very small percentage of the potential audience of that show, what is the "correct" way to treat it? I personally sort of like the "low sensory night" and "tell them when and how much" approaches, myself; those don't impact the neurotypical segment of the audience as much as cutting the cues completely. I think that it's probably a good idea for -- if not the entire performance industry -- at least each facility to have a Policy Statement on the issue, which can be extended as needed by producers and directors... and I think it's probably a good idea to err generally *away* from imposing too many limits in such a statement overall.

Has someone already created such a statement, in 5 sentences or less?

I guess this is one of those places where I'm largely libertarian (a view I got from Robert Heinlein just as much as I did my liberalism... which really freaks out the people who got their conservatism from him).


----------



## AlDenteUmber

@Jay Ashworth League of Chicago Theaters has a vague single sentence statement about commitment and a page of resources: https://leagueofchicagotheatres.org/accessibility-resources/. I'm personally not a fan of the policies about how much an organization cares, because the statement does literally nothing unless it is placing a restriction. It's the actions that make a difference. I would like to see every show have a nutrition-facts-esque run down of useful information that is posted both in the lobby and anywhere else you might buy tickets. When providing this information becomes compulsory, design teams will also be prompted to think about how these things may affect their neurodiverse audience members more often.


----------



## Lasermike

AlDenteUmber said:


> @Jay Ashworth League of Chicago Theaters has a vague single sentence statement about commitment and a page of resources: https://leagueofchicagotheatres.org/accessibility-resources/. I'm personally not a fan of the policies about how much an organization cares, because the statement does literally nothing unless it is placing a restriction. It's the actions that make a difference. I would like to see every show have a nutrition-facts-esque run down of useful information that is posted both in the lobby and anywhere else you might buy tickets. When providing this information becomes compulsory, design teams will also be prompted to think about how these things may affect their neurodiverse audience members more often.View attachment 20843



I like this, gives me what I need to make a good decision without too much jargon nor giving away the plot. I can see that I'd be able to handle the lights and sounds without issue as the duration is short enough that it won't trigger a reaction. I don't really need low sensory, I just need to know it won't be the entire first act.

Michael


----------

