Maybe you’ve heard about the video game Fortnite that now has 45 million players? One reason it’s so popular is that it’s free to download — with its seizure-inducing graphics.
Playing Fortnite involves quite a bit of shooting that creates bright flashes. The flashes are especially likely to trigger seizures when the game is played in “high explosives” mode (available during limited release dates). The high explosives create bigger explosions splayed across larger areas of the screen, which in turn affects a greater number of neurons in the brain’s visual processing system. For reasons not entirely understood, in people with photosensitive epilepsy, flashing light and certain other visual stimuli overload the visual cortex in a way that leads to seizures.
In one user-uploaded, 7-minute, 39-second gameplay video using high explosives, 8 separate image sequences failed to meet the standards for minimizing the risk of visually triggered seizures. Each of those failures represents a visual sequence with a reasonable chance of setting off seizures in persons who have photosensitive epilepsy. The test for seizure risk from images is based on guidelines for reducing visually induced seizures, determined by extensive research on the image qualities that can bring on seizures in people with photosensitive epilepsy: motion, brightness, contrast, patterns, color intensity, and flash/flicker .
Please fix this, Epic!
Fortnite’s developer, Epic Games, has come out with remarkably frequent product updates to address performance bugs and keep players’ interest from flagging. (No issues with maintaining players’ interest level — maybe you’ve also heard about parents and teachers struggling to handle kids’ unprecedented preoccupation with this game?) Last week Epic removed a guided missile weapon from the game — for now — due to a bug and some player feedback that using the weapon disturbed the sense of fairness and balance of the game. That still leaves grenades, rocket launchers creating big flashes in high explosives mode.
Perhaps the company’s unusually rapid product development cycle would make it possible to modify all the game’s graphics where the image sequences place users at risk of seizures? There are tools available to developers to identify the offending images — what I use to test the gameplay clips is just another version of the same Harding Flash and Pattern Analyzer software. You can read here about the way I do the testing.
Should you be concerned?
Maybe. Estimates are that up to 3 percent of the population has photosensitive epilepsy (among those with any other form of epilepsy, about 5 percent). Photosensitive seizures typically begin between ages 8 – 20, and they can occur in people with no history of epilepsy. Of the hundreds of children who had seizures during a 1997 Pokémon cartoon broadcast in Japan, researchers found that 74 percent of them had never been aware of experiencing a seizure before.
Prevalence of photosensitive epilepsy is probably underestimated because seizures are not always noticeable, and therefore they are not always reported. The symptoms of a mild seizure may be so subtle that nobody realizes what’s occurred. That doesn’t mean a mild seizure is nothing to worry about; any seizure has the potential to leave disabling physical and cognitive after-effects and mood changes that can last for days.
What can you do?
Parents and teachers are struggling to handle kids’ unprecedented preoccupation with Fortnite. To learn about the effects of video games on the central nervous system, and about finding ways to reduce your child’s screen time, I recommend Dr. Victoria Dunkley’s Reset Your Child’s Brain: A Four-Week Plan to End Meltdowns, Raise Grades, and Boost Social Skills by Reversing the Effects of Electronic Screen-Time.
To learn if your child may be experiencing game-induced seizures, ask about any weird sensations occurring while playing video games. See if you can get the child to wear cobalt blue dark glasses while gaming; in these are extremely effective at protecting against or reducing the severity of seizures.
Riot Games, publisher of the hugely popular League of Legends game, responded quickly to a user reporting a seizure from the game. What happened this month is both a short and sweet case study in customer care, and a mystery.
Two days after a new animated log-in screen for League of Legends appeared, two users reported on a forum that the visual effects of that image caused a seizure. Several others said that the jerking of the image every few seconds produced uncomfortable and unusual sensations.
After the first user posted about his experience, Riot Games:
- took down and replaced the animated image
- announced the fix
- noted the company already uses software to test its games for seizure-triggering images and added, “…but if that isn’t enough we need to know.”
- thanked the user for pointing out the problem so it could be fixed
You can read the respectful exchange that unfolded in the League of Legends subreddit here.
In this instance, the fix was simple. Since the image sequence causing the problem occurs in an isolated part of the code, outside of game play itself. Riot Games simply replaced the login-in screen with a prior version. Riot posted this update: “We take this stuff super seriously and we’re grateful to [the original poster] for raising visibility on the issue so we could solve it.”
The mystery: What triggered the seizures?
On to the mystery. If Riot uses software to test its games for the possibility of triggering seizures, how did this image get through the testing process? Looking at the image (I do not have photosensitive epilepsy) it doesn’t show obvious violations of image safety guidelines. Because there’s an interval of some seconds between the periodic vibration of the image, those shifts don’t create a flashing effect. (One user described it as a “shudder.”) And there are no bold patterns that trigger seizures in some individuals.
I ran the image sequence through the seizure guidelines test software and, sure enough, the periodic shake barely registered. I consulted Prof. Arnold Wilkins of the University of Essex, a leading researcher in visual effects that influence the brain.
He examined the sequence frame by frame (video typically runs at about 30 frames/second) and found a single blurred frame in each “shudder” that differed from the rest. He suggests that the resulting disruption in an otherwise stable image is “profoundly disturbing” to the visual system. Prof. Wilkins advised that even wearing colored lenses, which are remarkably effective in reducing or eliminating seizures triggered by flicker, probably would help only slightly in this instance.
No guarantees of safety
While many of the guidelines for seizure-causing images have been carefully defined through research, we clearly don’t know everything yet. So even developers who follow image safety guidelines and test their products for a gaming experience without seizures can produce visual effects that are unsafe for those with photosensitive epilepsy.
Five of New York Magazine’s top ten video games of 2016 don’t meet guidelines for reducing the risk of visually provoked seizures. Developers of these popular games could have designed the visuals in a way that lowers the seizure risk to users, but didn’t.
Guidelines for reducing the risk of seizures triggered by video images were published in 1994, when the UK required that all TV programs and advertisements meet those visual safety standards. The same guidelines for making television images safer could easily be adhered to when developing video game visuals. No regulations on seizure-inducing images in video games have ever been enacted, so game developers have no incentive to work within the guidelines.
Instead, for many years game publishers have provided a seizure warning that makes it extremely difficult for consumers to take legal action in case of a seizure. Some games may in fact conform to seizure-reduction guidelines, but because the seizure warnings appear on all games, consumers can’t know which ones are riskier. The warnings began appearing in 1991 in response to the first video-game-seizure consumer lawsuits.
What compliance with the guidelines means
Many popular games don’t meet the guidelines, as demonstrated by my testing of New York Magazine‘s favorite games. A couple of the failing games were among the top five first-person shooter games selected by Forbes.
I tested video clips from gameplay and promotional trailers for the games on the list using software that identifies video sequences that don’t comply with the guidelines. The software is designed for game developers and video producers to test their moving images for compliance.
Note that for the games that didn’t violate the guidelines, rather than list them as passing the compliance test, I’ve indicated that they did not fail the test. Although in previous posts with test results I’ve listed games that “passed” the guidelines test, I’m no longer using that terminology. That designation could too easily be misinterpreted to mean that such games will definitely not cause seizures.
Even if a game doesn’t fail the guidelines compliance test, there is still a risk of seizures, for several reasons:
- I may not have tested a portion of the game with problem image sequences
- The guidelines aren’t fool-proof. They are designed to prevent seizures in approximately 97 percent of people who have photosensitive epilepsy, the condition where visual stimuli can trigger seizures.
- Many environmental and personal health variables–such as lack of sleep or illness– can affect an individual’s vulnerability to seizures
Do you need to worry about seizures from video games?
- The vast majority (97 percent) of people diagnosed with conventional epilepsy can play video games without risking a seizure because–unless their EEGs indicate otherwise–their seizures aren’t triggered by visual effects. These people don’t want others questioning their fitness for gaming.
- People with no history of epilepsy may be most at risk. Seizures can be triggered by flash and flicker even in people with no history of seizures, which means that many don’t know they are at risk of having a visually triggered seizure until a video game brings on their first event. Of the children who had seizures during the 1997 Pokémon cartoon broadcast in Japan, only 24% had previously experienced a seizure.
- Visually triggered seizures typically begin between ages 2-18, and most commonly begin around age 12-13. Of patients age 7-19 who seek medical attention for a seizure, ten percent test positive for photosensitive epilepsy. Researchers estimate that only 25 percent of people outgrow the condition, typically in their twenties.
- It is relatively unusual but not unknown for these seizures to develop in adults. Because in many individuals a number of factors (for example, emotional state and hormone levels) affect seizure vulnerability, a seizure may not actually occur until several of these factors are present simultaneously. Even one seizure can be life-changing if it results in injury or permanently bars an individual from certain occupations.
- It is also possible to experience subtle seizures and not realize they happened. This doesn’t mean there are no seizure consequences, though. Typically after seizures one’s physical, cognitive, and emotional functioning can be impaired.
More on the guidelines and how games are tested for seizure risk
None of the five video games picked by a Forbes reviewer as the year’s best first-person shooters meet safety guidelines for reducing the risk of visually triggered seizures.
The fast-moving, flashing images in these five games could provoke seizures in people whose seizures are triggered by visual stimuli, due to a sometimes hidden condition called photosensitive epilepsy. I tested image sequences from these popular games using software designed for checking the adherence of images sequences to the seizure reduction guidelines. All five failed:
Game developers could — should — use this same technology to build products compliant with the guidelines! The application I used to test the games for compliance isn’t a consumer product; it’s intended for developers. Instead of building games that comply, many developers simply place seizure warnings on games and consoles. People with no history of seizures don’t pay much attention to seizure warnings, though. Why would they?
Reason #1 consumers don’t know they may be at risk
Photosensitive epilepsy most often develops in adolescence and remains hidden until it’s activated by particular stimuli and circumstances. If earlier in life visual stimuli didn’t trigger an event, how does one know that’s no longer true?
According to one study, 74 percent of individuals with photosensitive epilepsy first learn they have the condition when they experience a seizure in the presence of flashing lights or another visual stimulus. This study was based on the histories of hundreds of children who had seizures during a 1997 Pokémon cartoon broadcast in Japan.
Sometimes the first seizure triggered by a video game can have life-changing consequences. A Navy pilot who played Oblivion, had a seizure that produced injuries and resulted in permanent loss of his flight clearance. Think of the medical testing he underwent before he was trained to fly–obviously his seizure vulnerability had not yet developed.
Reason #2 consumers don’t know about their risk
Some seizures aren’t noticeable. This means that included in the 74 percent who (think they) never had a prior seizure, there are some people who may already be experiencing them without realizing it. Subtle seizures involving no body movement may not draw the attention of others nearby, either.
People with no history of seizures aren’t aware that undetected seizures exist and therefore may dismiss any unusual physical or mental sensations while gaming. If the seizure causes a loss of awareness for a few seconds, the person will not be “present” at that moment to recognize what’s happening or remember it later. For more on undetected seizures, see the section “Research shows people often don’t detect their own seizures” in this post.
Note that undetected seizures as well as more obvious events can bring on a range of disabling physical and cognitive after-effects and mood changes that can linger for days.
Not all video games violate the image safety guidelines. Even though video games typically carry seizure warnings, the warnings don’t reflect the seizure risk of any particular game. Unfortunately, consumers have no way of knowing which games are in compliance and which are not.
Let’s say you’re an informed consumer, aware that some games can pose a seizure risk and you’d prefer not to take that risk. You understand that a game with lots of bright flashing is more likely to be a problem, but you can’t really know whether a specific game that you want to play is more likely to trigger seizures. How can you play only games that meet guidelines and avoid only the noncompliant ones? (This is where the testing I can do can identify certain cases of noncompliance.)
- The vast majority (97 percent) of people diagnosed with conventional epilepsy can play video games without risking a seizure because their seizures aren’t triggered by visual effects. These people don’t want others questioning their fitness for gaming.
- Want to know more about how I test video games? About the image safety guidelines? Read here.
- For the record, Forbes states that opinions of contributing writers (such as this guy who picked the five games) are their own, not the magazine’s.
In recent weeks photosensitive epilepsy received some media attention because of two developments in the 2016 presidential campaign. Who would have thought? While the public probably didn’t learn much about photosensitive seizures in either case, perhaps both situations contributed something to public awareness of seizures triggered by certain lighting effects and images…
Clinton’s blue sunglasses
After Hillary Clinton’s widely publicized medical emergency on September 11, various bloggers and political writers rushed to speculate about possible causes of the episode. Photos of Clinton taken that day showed her wearing sunglasses that appeared dark blue, and some people wondered whether the glasses provided a clue to an undisclosed medical condition.
Visits to this blog surged for several days. More than 95 percent of the nearly 24,000 visitors from September 11 – 13 read two of my prior posts about blue lenses that protect against visually induced seizures. A few readers questioned whether the sunglasses seen on Clinton were the type worn to prevent photosensitive seizures.
My answer was maybe yes, but probably not. Since photos of Clinton that day showed her wearing them outside during the day, they weren’t likely worn for seizure protection. Flickering light doesn’t generally trigger seizures outdoors in daylight and good weather—for flicker to occur there has to be an extreme contrast of light and darkness in rapid succession. It’s certainly possible to have photosensitive seizures triggered outside in daylight, in specific situations: sunlight reflected on a body of water, or a line of trees seen from a moving vehicle, where sunlight is broken up by trees alongside the road. But Clinton was not in those settings when wearing the glasses.
Seizure-inducing images tweeted by angry reader
In a separate election-related incident, the matter of photosensitive seizures was taken in a troubling direction. In response to articles he wrote critical of Donald Drumpf, Newsweek journalist Kurt Eichenwald received a menacing tweet from an unhappy reader that referred to Eichenwald’s epilepsy and included an embedded video of flashing images. When the video started, Eichenwald dropped his iPad before a seizure could develop.
It certainly wasn’t the first time seizure-inducing images were placed online for the purpose of triggering people with photosensitive epilepsy, but it’s the first instance I’m aware of that’s tied to this rancorous political season. Criminal defense attorney Scott Greenfield claimed in his blog that the episode qualifies as an attempted assault. “Yes, even Twitter can be used to commit an assault, regardless of whether Eichenwald was a victim,” he wrote.
For more on the legal and technology issues raised by the tweet to Eichenwald, check out this Future Tense article, in which UC Davis law professor Elizabeth Joh concludes, “…the existing tools of criminal law probably do address a tweet likely intended to harm its recipient or to create a reasonable apprehension of fear in him.” But she adds, “That doesn’t speak to the likelihood of prosecuting the troll, which may be low.”
What do a pineapple playing tennis and a grape going for a ride have in common? Two things: 1) They’re currently appearing in Google’s Olympics-themed iOS and Android Doodle Fruit Games app, and 2) viewing them in Google’s video promoting the app could give you a seizure.
For the next two weeks while the game app is available, Google is promoting it with a zippy, fast-paced trailer. Visitors watching the trailer see rapidly moving images images that could provoke seizures in anyone with a condition known as photosensitive epilepsy. I tested the trailer for its risk of inducing seizures and found two segments–involving the aforementioned pineapple and grape–with a flashing effect that could trigger photosensitive seizures. From what I can tell, the problem images appear only in the trailer and not in the games app itself–unless they appear only after players achieve a high score that I didn’t reach.
What is photosensitive epilepsy?
Photosensitive epilepsy is more common than is generally known, and researchers agree it is probably underestimated. People with the condition have epileptic seizures triggered by lights or images that flash faster than three times per second.
It gained some notoriety after a Pokémon cartoon shown on Japanese TV in 1997 sent nearly 600 children to emergency rooms with seizure symptoms. The condition had already been extensively studied and researchers had drawn up guidelines for reducing the seizure risk from video images, but at the time Japan did not protect TV viewers from problem images.
Who is affected by photosensitive epilepsy?
The vast majority of those with “regular” epilepsy are not affected by visual stimuli. But photosensitive epilepsy may be harder to detect and is underrecognized by the public and by doctors. You may be susceptible to photosensitive seizures and not even realize it since:
- Photosensitive epilepsy typically doesn’t develop until adolescence.
- It can occur in people with no history of seizures. Of Japanese children affected by the Pokémon cartoon, 76 percent had never before experienced a seizure.
- People with other forms of epilepsy are routinely tested for photosensitive epilepsy, but the condition may be most common in individuals who don’t have any other type of seizures. These people are very unlikely to be screened for it.
You can already be experiencing seizures and not know it.
- Not all seizures involve complete loss of consciousness, falling, or body movement observable by others. Such major events, known as generalized seizures, occurred in less than half of the Pokémon-affected children.
- Because consciousness is altered at the time, a person having a seizure often has no memory of it.
Even if you have no visible symptoms of a seizure, there can be lingering after-effects that include fatigue, sleep, learning, and memory problems, mood irregularities, among others.
How the media and entertainment industry can reduce seizure risk
More than 20 years ago, researchers studying photosensitive epilepsy defined the factors, in particular the flash frequency, that are most likely to provoke visually induced seizures.The UK has required all TV content to conform to seizure-reduction guidelines since 1994, and Japan enacted similar regulations following the Pokémon incident. To date, no other countries have done this, but a United Nations-affiliated agency did adopt recommendations for reducing photosensitive seizure provocation from television. Meanwhile, of course, interactive media have become a much bigger part of our lives than television, and the same guidelines for reducing seizures from TV should be adapted to the internet.
The World Wide Web Consortium (WC3), the international group that produces website accessibility standards for all types of applications, now includes guidelines for reducing the risk of visually triggered seizures. But incorporating such standards into private industry applications and sites is a hugely complex and time-consuming process.
The United States Department of Justice has been considering since 2010 the complexities of creating regulations ensuring access by the disabled to public and private websites. The DOJ announced this spring that rules governing private websites have been delayed until 2018 at the earliest.
In 19901, after a few consumer lawsuits were filed due to seizures, game developers began including a seizure warning that has kept consumers from filing or winning such lawsuits. Although most game documentation and packaging contain a seizure warning, not all games contain seizure-provoking visuals. Consumers don’t know which games actually have potentially harmful sequences and largely ignore the warnings.
How you can prevent photosensitive seizures
If you’re susceptible, even a brief exposure of a few seconds to flashing can be enough to bring on a seizure. If you know that you are vulnerable to these seizures, there are some precautions doctors recommend to avoid being triggered:
- When possible, avoid situations and stimuli that are likely to be provocative, including emergency lights, electronic billboards, video games, light shows, flickering fluorescent lights, fireworks, animé and other fast-moving cartoons
- Wear blue-colored glasses, which filter out the most provocative light frequencies. Most opticians can make these inexpensively.
- In the presence of flashing light, cover one eye.
- Increase your distance if possible from the flashing image–so, for example, stay at least 6 feet from your TV screen, and don’t play video games up close.
- Don’t play when fatigued or sleep-deprived.
- Take frequent breaks during prolonged exposure–although this won’t always help if you are triggered in a matter of seconds.
Testing for visuals that can provoke seizures
I tested the trailer using an industry-standard application called the Harding Flash and Pattern Analyzer that detects image sequences that can trigger photosensitive seizures. It is based on algorithms devised by Graham Harding, one of the world’s leading experts on photosensitive epilepsy. The application is widely used by producers and networks in the UK—including by the BBC—to reduce the risk of seizures from material on broadcast TV. The analyzer examines video sequences frame by frame for very specific and measurable image qualities that researchers have found can trigger seizures.
Seizures from video shown on TV about 2012 Olympics logo
This is not the first time that Olympics-themed promotional visuals have placed viewers at risk of seizures. A promotional video for the logo of 2012 London Olympics logo shown on British TV news in 2007 resulted in seizures in some viewers. It had not undergone the required testing that would have alerted producers to the problem prior to broadcast.
Terrible idea. Take a genre of video games—first person shooter– that is especially likely to provoke seizures. Make an action movie filmed entirely in that style. Put it on the big screen for release in theaters. The larger an image is, the greater the area affected in the brain’s visual cortex, and therefore the risk of visually triggered seizures is increased in those who are vulnerable.
Hardcore Henry opened (and in most cases, also closed) in theaters this month. It’s described by the student newspaper of Washington College as 90 minutes of “non-stop chase scenes, splatterhouse shootouts, and barely comprehensible fistfights that often end in ridiculous dismemberment.” Glenn Kenny’s New York Times review explains the film’s R rating thusly: “for not letting a minute pass without subjecting one character or another to grievous bodily harm or worse.”
I suppose it’s possible to produce such subject matter without seizure-inducing images, but given such descriptions of the content, I wanted to check. Without going the movie. So I tested** the movie’s promotional trailers for compliance with seizure reduction guidelines. The guidelines were designed to protect all but 3 percent of those who may have seizures triggered by visual stimuli. After watching the trailers (I do not have photosensitive epilepsy), I was not at all surprised that the movie does not comply.
This is hardly the first movie to include images that could trigger seizures. But based on the trailers and reviewers’ accounts of a relentless pace of action, most likely there are many potential seizure triggers during the film. Researchers of photosensitive epilepsy believe there is a cumulative effect on the brain; the risk of a seizure increases after prolonged exposure to potential triggers.
Strong stomach required
Many reviewers of Hardcore Henry cautioned readers about motion sickness. One reviewer interviewed the movie’s producer about apparently significant (yet not entirely successful) efforts to minimize it. The producer said those efforts were begun long before film production began, with many tests and test screenings.
Some representative remarks:
“…many people are going to feel ill when they try to watch Hardcore Henry on the big screen…make sure everyone in your party either has no issue with motion sickness, has taken their Dramamine, or rolls into the theater with an empty stomach…” — The Daily Dot
“…as I waited for my nausea to subside, I began to appreciate the dastardly marketing plan built into Hardcore Henry: It’s essentially a dare to see if audiences can finish the whole thing without throwing up.” — Vox.com
“Hardcore Henry will probably go down as the film of 2016 that is most likely to make you feel nauseous from watching it (due to motion sickness, that is, not the gory, over the top violence).” — Screenrant.com
Back-handed seizure warnings
A number of reviewers mentioned seizures, but not with the same concern with which they write about motion sickness. Sure, motion sickness is unpleasant, but a seizure is not only unpleasant, it can be dangerous and life-altering, and its effects on the brain can linger. You wouldn’t know it from these reviewer comments, though:
“It’s remarkably watchable, in fact, with none of the motion sickness you might expect, which is especially amazing given the film’s unswerving dedication to full-bore, seizure-inducing action.” – The Georgia Straight
“…Hardcore Henry is a 90-Minute Cinematic Seizure…a frenetic editing style that can make you feel like you’re having some kind of seizure…I don’t see how anyone could watch it and not experience motion sickness…I definitely felt like I’d suffered from some sort of brain trauma when I walked out of the theater. (Can you get a concussion just from watching a movie?)” — Esquire
Treating seizures (and those who have them) with respect:
Just 2 reviews of dozens I read seemed to be genuinely concerned about the movie’s potential to trigger photosensitive seizures in audience members:
“If 3D gives you a headache, Hardcore Henry is enough to bring on epilepsy.” — Moviehole.net
“I left the theater wondering if the jittering, disoriented feeling I had buzzing through my skull was some sort of sudden onset epilepsy.” — University News
If you live in the UK, there are real warnings about the risk of visually induced seizures. Listings for movies with images that don’t comply with seizure reduction guidelines warn of “a sequence of flashing lights which might affect customers who are susceptible to photosensitive epilepsy.” That’s because the UK regulates the appearance of TV, movies, and advertising to protect those individuals. Some of these people with photosensitive epilepsy don’t realize they have the condition. It may have developed only recently or it’s quite possible they were never aware of experiencing a seizure. Not all seizures look like what you typically see portrayed.
What lies ahead?
What’s most worrisome is that the consensus among reviewers — regardless of how well they liked Hardcore Henry — is that the influence of video games on movie-making is only going to grow.
“Virtual reality is on the way. Video games and movies will soon start to blend and borrow from one another in many ways. And this movie, imperfect and nasty and often astonishing, is a vanguard.” — Slashfilm.com
“…the visual language of games will soon come to have as much of an impact on up-and-coming film directors as cinema does… and it’s safe to say that we won’t be short of films based on video game properties…With an increased push towards the home viewing experience in movies and interactivity in media, it will be interesting to see how the cinema of tomorrow is influenced by gaming perspectives. “ — Den of Geek
We will certainly see more of the first-person perspective, too. Some hailed the project as a technical marvel and “a revolutionary approach to narrative filmmaking.”
**How I tested the movie trailer
I run downloaded video clips through an application called the Harding Flash and Pattern Analyzer. (Graham Harding is one of the world’s leading experts on photosensitive epilepsy.) The FPA is widely used by producers and networks in the UK—including by the BBC—to reduce the risk of seizures from material on broadcast TV.
The analyzer examines video sequences frame by frame for very specific and measurable image qualities that researchers have found can trigger seizures. When such images are found, it displays and indicates the specific frames that violate seizure reduction guidelines. Violations occur with:
- rapidly alternating light and dark images (flash/flicker)
- certain stripes and geometric patterns with high contrast
- large areas of very bright (“saturated”) red
- problem images that take up more than one quarter of the total screen area