Have you ever wondered whether the flash from a speedlight or a studio strobe could damage someone’s eyes? After all, they can be mighty bright! On the other hand, photographers have been using flash for decades. You’d think that if there was a problem, it would be pretty widely known by now. Models and celebrities have been photographed thousands of times with flash and haven’t gone blind. Heck, my optician uses a pretty darn bright flash when taking a photo of my retina. So, what’s the story?
Back in 2015 there was a brief furor after the Daily Mail, a UK tabloid with occasional stories of dubious veracity, ran a story from China which claimed that a three-month-old baby had been permanently blinded in one eye by a photographer using flash in a close-up photo. The fact-checking site Snopes.com tracked the story back through several iterations and questionable sources, yet was unable to find any details about the story (like the names of the parents) nor were there any references to a doctor’s diagnosis. Most maternity wards in hospitals allow, even encourage, flash photography of newborns and a few explicitly state that flash won’t hurt a baby. However, the internet being what it is, this story pops up every once and a while.
Yes, there are ways that extremely bright lights can damage someone’s eyes. However, photography flashes, at least for the vast majority of people in the vast majority of circumstances, aren’t harmful.
There is something called “flash blindness,” when the retina gets too much light and you can’t see clearly. Sometimes you just see a very bright spot for a while. However, flash blindness is a temporary condition. As the retina returns to normal, so does your sight. If you’re looking directly at a speedlight or studio strobe as it flashes, you’ve probably experienced flash blindness. And your sight returned to normal in a matter of seconds.
Please note that I am not an ophthalmologist nor a medical doctor. What follows is based on some substantial research, but should not be considered definitive advice for everyone or anyone. This article just synthesizes what I’ve found over the past few weeks of research.
How Can You Damage Your Eyes?
There are basically two ways your eyes can be damaged from light. First, through a thermal reaction where the light heats up eye tissue and cooks or burns it. Second, through chemical reactions in which photons of light are powerful enough to break the bonds of molecules, leaving free radicals and damaged molecules in their wake.
And there are two ways to make that damage happen: through exposure to extremely bright light for a period of time or to extremely focused light, also for a period of time.
You’ve probably heard that you shouldn’t look directly into the sun. That’s because the brightness of the sun, combined with the UV light it emits, can damage eyes. If a light is too bright, it can overstimulate the retina, that part of the eye that converts light into images. In that way, it’s kind of like a camera sensor. The retina then sends image information to the brain via optic nerves. When very bright light hits the retina, it can overstimulate the retina’s cells, which release too many chemical signals, which can damage the back of the eye. A glance at the sun isn’t a problem. Staring at the sun for a prolonged period of time is. As with the retina, your camera’s sensor can be damaged by long exposure to the sun, especially when the rays are concentrated by the lens into one spot.
The flame of a welder’s torch is also extremely bright and can cause eye damage with prolonged exposure. That’s why a welder’s protective gear includes very dark glass. Welder’s glass is recommended by some for viewing a solar eclipse.
Highly-focused light can burn the eye. That can be a good thing, like using lasers to repair a detached retina. Or it can be a bad thing, when a highly-focused beam of light burns part of your retina. Think of how a magnifying glass can concentrate the sun’s rays and set fire to a piece of paper. (Most DSLR manuals warn against looking through the viewfinder directly at the sun, for this reason.) The same thing happens with powerful lasers—one reason airlines and the FAA are concerned about a few instances of people shining lasers at aircraft cockpits.
Meanwhile, UV-A rays can damage the macula, responsible for your central vision, and UV-B rays can damage the front part of your eyes. Excessive UV light exposure is associated with macular degeneration, cataracts and pterygium, a growth that blocks part of the cornea. A hefty bout of exposure to sunlight and glare, like a long sunny day at the beach or on the ski slopes, without sunglasses, can result in photokeratitis, or corneal sunburn. Speedlights and studio strobes have filters that block the UV light they emit. (In order to do UV flash photography, you need a specially modified camera, special UV lights or flash with the filters removed, and special glasses to protect your eyes.)
There is some evidence that Caucasians and people with blue eyes are more susceptible to damage from light exposure. And there was a study of Chesapeake Bay watermen, who spend their days dealing with bright, reflected light on the water, found that prolonged exposure to blue light increased the risk of age-related macular degeneration. There are also several medical conditions which make people somewhat more susceptible to eye damage from light.
Three Reasons Flash is Safe
Length of Exposure
Several sources stated that you’d have to be staring at the sun for a while, 15 to 30 seconds, before starting to get permanent damage in your eyes. Long before that, the brightness would be painful enough you’d likely close your eyes anyway. The journal JAMA Opthamology recently discussed a case where a 12-year-old Florida girl had damaged her retina after staring at the sun for about one minute.
While a flash is bright, it often only lasts a tiny fraction of a second. Even repeated firings of a flash only sum to a fraction of a second. A lot of speedlights have a flash duration of between 1/200 and 1/20,000 of a second. Many studio strobes have a duration of 1/200 to 1/5,000 of a second or less. Twenty flashes of a studio strobe at 1/1000 of a second might only amount to 1/50th of a second total exposure.
While it may seem bright, studio strobes and speedlights aren’t all that intense. Light falls off dramatically the moment light leaves your flash because of the way it spreads out. It begins to lose intensity according to the inverse square law. If your flash illuminates an area of one square foot at a distance of one foot, it will illuminate an area of four square feet at two feet, 9 square feet at three feet distance and so on. If a flash seems really intense at a distance of one foot, doubling the distance to two feet means only one quarter as much light hits the subject at any one point. Double that again to four feet away and the light will have only 1/16th of the intensity it initially had. Move to eight feet away and only 1/64 of the intensity remains.
It’s even less intense if you’re using bounce cards, diffusers, umbrellas, soft boxes and gels.
Not Highly Focused
While speedlights and studio strobes can be bright, they’re not very focused, even if you put a snood on them. The light spills and bounces in all directions. The farther the light is from the subject, the more diffuse it is. For an exercise, take a laser pointer and point it at a wall. See if you can get any combination of flash gear and modifiers to focus the flash light down that much. Impossible! Move the flash back a bit and it is even more difficult to focus it down to a small area.
As you’ve seen, there are several ways light can damage your eyes. Unless you suffer from some specific condition that makes your eyes especially susceptible to injury from light, flash photography isn’t going to be a problem.
So, fire up those strobes and warm up your speedlights. Shoot away. Your subject is probably doing far more damage to their eyes during their beach or ski vacation than your flash will ever do.