How bright a flash is safe for the human eye?

**Mark Sawyer** · 20-Nov-2012, 11:06

I have access to a very bright flash. Very, very bright. Think military night-time aerial reconnaissance bright. I can tame it down with a soft box and the choice of diffusion, but before I use it for (wet plate) portraits, I'd need to know if it's safe, and probably get an opinion from an opthamologist or two. But I thought I'd ask here too... any thoughts? Everything on the web says strobes, even the brightest studio strobes, are fine, but this one's a bit above that...

**Ed Richards** · 20-Nov-2012, 11:34

Google Chuck Close daguerreotype

He used super strobes to make instant daguerreotypes.

**John Olsen** · 20-Nov-2012, 11:39

You're not going to make any friends if you use something that strong. A full Speedotron 2400 in a portrait setting will make for a very stressed-out sitter. Anything more, and you'll just hear a slamming door as they leave. From laboratory experience, 10-100x a Speedotron will leave a burn spot on the retina. I wouldn't trust an ophthalmalogist to know a safe level of exposure, having been exposed to a carbon arc eye exam by one.

**Bob Salomon** · 20-Nov-2012, 12:49

When I was in the USAF and doing aerial reconnaissance on 10" roll at night our flashes were aerial bombs rather then strobes.

**Bob Salomon** · 20-Nov-2012, 12:54

Originally Posted by Mark Sawyer

I have access to a very bright flash. Very, very bright. Think military night-time aerial reconnaissance bright. I can tame it down with a soft box and the choice of diffusion, but before I use it for (wet plate) portraits, I'd need to know if it's safe, and probably get an opinion from an opthamologist or two. But I thought I'd ask here too... any thoughts? Everything on the web says strobes, even the brightest studio strobes, are fine, but this one's a bit above that...

I was the Broncolor rep when they introduced their 6000ws studio flash. While installing one in a NY City studio an assistant climbed up a ladder to adjust a head with an elliptical reflector that was set to full power. While he was adjusting its position someone turned the pack on and fired it while he was looking directly into it from a couple of feet away. Somehow he kept his balance on the ladder and was able to climb back down. He saw spots for a while but was otherwise OK.

This should not be a recommended practice but that flash was probably a good deal more powerful then what you are considering.

**E. von Hoegh** · 20-Nov-2012, 12:55

Harold Edgerton demonstrated an aerial strobe by holding a sheet of brown paper in front of it, about 2 feet away. It burst into flame when the strobe was triggered.

**Jason Greenberg Motamedi** · 20-Nov-2012, 12:59

Much of this will also depend on how you are modifying the light. I use a 9600w/s Speedotron head, and can tell you there is a pretty major difference in how my subjects react to the head in a beauty dish (for wet plate this is about f8 at 6 feet) and a 16" sport reflector (about f14 at 6 feet). After the beauty dish I usually hear usually "wow," and then they get up and move away, with he sport reflector they say something more descriptive, and cover their eyes for a minute or two, before looking around and telling me they still see spots. I have subjected myself to all of these, and can tell you that it is a little jarring (it makes a loud pop!), but the effect (seeing spots) wears off very quickly.

**Mark Sawyer** · 20-Nov-2012, 13:15

Thanks, guys! Ed, some of the stuff I read in this thread: http://www.largeformatphotography.in...rotypist/page2 was scary, (a couple of quotes from that thread) below)

Originally Posted by Ed Richards

He also used some limited nuclear blast as a flash so they could be really short exposures to do away with motion artifacts. He might have been kidding, but in the story I read he claimed the models got instant sunburn.

Originally Posted by Jason Greenberg Motamedi

I can't recall the exact details, but Close (read: Spagnoli) used some incredibly powerful stobes to take the images at f3.5. Jerry told me that you could smell burning hair after the exposure.

John, we used 2400 w/s Novatrons (sometimes several) in my old highschool studio with no problems other than the kids setting them off to annoy

Bob, this is a fairly modern strobe, so I'm not sure how it would compare, but it's reassuring that your friend survived with his eyesight intact. I'll try to find out what the watt/second rating is on this thing.

E, Edgerton's strobes would have been different technology than this, I suspect, but if I con't use them for portraits, maybe for roasting marshmallows?

Jason, much thanks! If I go with this, I'm sure it will be in a soft box, and I'll have my choice of diffusion material. I should experiment with my 2400 w/s Novatrons on wet plate still lifes and see what they do...

I'll keep researching this, any further comments are more than welcome!