Flash photography used to be pretty wild
It’s not much of a secret that photography used to be, uh, difficult. You didn’t just whip out the communication device you always have on you to take a snapshot, you needed to carry an actual camera around with you like some kind of tourist. And it was also expensive! Every picture you took used up a frame of film which cost money to buy, and then there was the processing fees and the time - unless of course you had a Polaroid camera. But what’s perhaps less well-known (at least among the whippersnappers) is that there was a time when using flash photography added yet another cost to every photo you took. See, photographic film usually isn’t all that sensitive. It needs a lot of light to correctly capture an image, especially color films with fine grain.
During the day, that miasma of incandescent plasma in the sky lights up the world plenty for a camera to make some memories, but at night, or even just indoors under artificial lighting, film cameras need some help. And a lot more than the little LED on your smartphone has to offer. Flash photography in the days of film involved equipping a camera with its own light source roughly as bright as the sun. That may sound pretty difficult, and it should because it was.
The sun, not sure if you know this, is pretty stinking bright and replicating that amount of light in something you can carry around with you was quite challenging. But we did it. You’re probably familiar with electronic flash units that use flash tubes.
These are still in common use today and they achieve sunlight-rivaling output by shoving a big electrical discharge through a quartz tube filled with xenon gas. Charge a big capacitor up with perhaps a dozen joules of stored energy and when you dump all that through the tube in a tiny fraction of a second, it will ionize the xenon producing an extremely bright flash. [shutter/film winding] The energy involved is fairly modest, but because the discharge happens over such a small fraction of a second, the instantaneous power of one of these flash tubes is well into the megawatt territory. They’re bonkers.
For many years, the technology which made this possible was quite exotic. Though invented in 1931 by Harold “Doc” Edgerton, flash tubes spent decades relegated to scientific research and other specialized applications. General photographic flash units using the technology did come to market around the mid 1950’s but they were just way too expensive for anyone but professional photographers to afford. Still, amateur photographers taking snapshots at birthdays and on vacations weren’t left in the dark: consumer flash photography was alive and well, no fancy technology required.
How? With these! These are flashbulbs. They look kind of like an ordinary incandescent light bulb, except something went very wrong when making the filament. You’d use these things with a flash unit like this.
Stick a fresh bulb in its socket, pop the unit onto the hot shoe of a camera, engage its adorable little reflector, and then, when you took your next photo, the flash unit’s battery (once triggered by the camera through the contacts on the hot shoe) would send power to fire the flashbulb once the camera’s shutter was open. That would produce an extremely bright flash which would illuminate the camera's field-of-view to expose the film correctly. But that flash happens very quickly. To get a really good look at one of these, I’m gonna need some kind of a… slow mo guy. Luckily, I have one right here! Hello! Hi Gav, how ya doin? Good, thanks, Alec! [laughs] -Thank you very much for having me here in Austin! Yeah, thanks for coming to my big, empty room.
I am using Gav’s expertise in slow-mo filming (and also equipment) because I want to film some old-school flashbulbs. Do you know how these work -Not really. So, this is basically a light bulb but what it’s filled with is metal shavings of zirconium and oxygen.
So this is a pure oxygen envelope, and when you send some electric current through there it’s going to cause the zirconium to burn extremely fast. So, a single-use bulb. It’s a single use bulb, it’s going to make an extremely bright flash, and then you gotta get rid of it.
But what I’m even more excited to see is this. This is a flashcube, technically this is magic cube or Magicube ‘cause it uses once C, that’s not important. And these are mechanically actuated by the camera. So rather than need to have a battery to send power through here to set it off, these actually have some sort of a firing pin to create a discharge at the base of the bulb to set it off and I’m really excited to see what that looks like.
Me, too. I’ve never even heard of that. They’re pretty cool. So, we’re gonna see what we can do. Uh, it’s gonna be pretty challenging to film this uh, what do you think we’re gonna have to do here? I think, well I like to start around 1,000 frames a second and then learn that that’s probably not fast enough and then maybe switch cameras. We’ve got a ton of options with frame rate today so I think we’ll just learn as we go.
I think that’s probably the best option and the only good thing is these are not as instantaneously bright as an electronic flash because they do burn over some fraction of a second so overall it’s the same amount of light but spread over more time. So hopefully, it’s not too crazy. But let’s find out! Let’s find out. We have Gav’s goofy probe lens thing… -There is nothing goofy about this, that’s a normal looking lens alright? -no it’s not, but we are uh… we literally, I have no idea what to expect here because I would like to see the filament but I know it’s probably gonna wipe out - or blow out the exposure, but we’ll see. [Gav] I can preemptively stop the lens down a little. [Alec] Yeah that might be… we’ll find out.
But again, you don’t know the other thing about the coating? -Ah. -Uh, the coating is there for two reasons. One, to shift the white balance. It’s adding some blue so that way it is the correct white for daylight-balanced film. But the coating is also there for, uh, let’s call it structural reasons. [Gav] Oh.
I love that it’s basically a sealed chemical reaction with a built-in gel. Like, it’s like they've thought of every single aspect of this. [Alec] I don’t think they thought of it [laughs] I think they realized there are some, uh, collateral issues. -OK. Do I need, like, eye protection? -No, you don’t need eye protection.
Maybe for the bigger ones… Hopefully this works. In 3… 2… 1. [Gav] Ooh.
Wow. [Alec] There’s actually, I can see it in the light there was some smoke coming from it. [Gav] So… was that leaking out of the bulb? Or is that coming from the… -Yeah, you see... you see how it’s bulged on the side? The glass is cracked. -Oh wow! So it’s that hot? -It’s that hot! They pretty much explode. Oh wow! That is bright! Yeah that’s kind of uh, oh that’s cool.
OK so to see detail in there then we need to be… [Alec] Way stopped down. [Gav] How many of these have we got? -Plenty! -Wanna just do it again? -Let’s just do it again. 3… 2… 1… go.
You can see the smoke? -Yeah. So is it bulging front to back or from… -It’s, wherever the glass cracks the coating keeps it from exploding. [Gav] Okay, let’s have a look at that. Pfft! [Alec] This is gonna be the real challenge with the flashcubes ‘cause I don’t know how bright the detonation is. Alright, here we go again. 3… 2… 1… You could hear it crack.
[Gav][ Yeah that was nice, it was like a... bit of an ASMR crackle there. [Alec] Oh that’s close.
-Oh we’re getting close, there. - In 3, 2, 1 [Gav] Ooh, very smoky, that one. [Alec] Oh you can see a crack in the glass.
[Gav] Oh, yeah. Ooohh! Yeah a nice backlit crack. You can see it like, sooting up and then the crack happens. Chh! -This is great! -At 1,000 frames a second the crack, it just looks the same as if you're filing at normal speed. Like, glass cracks so fast that it’s gonna happen in one frame. [Alec] Yeah, yeah.
Your, uh, the video where you did the sheet that you painted the rainbow colors - that was really cool. Having gathered plenty of footage with the AG-1 flashbulbs, it was time to take a look at the flashcubes. These things were initially introduced to make flash photography easier and more approachable.
Individual flashbulbs are fiddly to deal with, become extremely hot once used, and even if your camera is fancy enough to support flash photography (which wasn’t always a given) it still required a second device to use: the flash unit itself. Now, it wasn’t all terrible - flash units like this often incorporated some sort of eject mechanism to help you deal with the hot, spent bulb, but you’d still need to carry this and a box of bulbs around with you in addition to your camera - plus do a little dance between every photo - just to take pictures indoors or at night. Oh, and also make sure you have the right battery in your flash unit and that it’s not dead. It was an ordeal.
In contrast, the flashcube neatly integrated four flashbulbs and accompanying reflectors into a simple-to-use, disposable… cube. Simply plop one onto the receptacle of a compatible camera and you could take flash photos, no extra equipment required. Cameras which used them would even rotate the cube automatically when you wound the film to the next frame. And since the bulbs were found behind a polycarbonate shield, not only did that help contain a ruptured bulb should that happen during the flash, but you never had to worry about burning your fingers or setting a trashcan on fire after you took a picture. The first flashcubes were introduced by Syvlania and Kodak in 1965, but those weren’t really that interesting. They looked almost identical to this later version, but they were essentially just four ordinary flashbulbs packaged in a clever way.
The bulbs were still electrically fired, so cameras which used the first iteration of flashcubes still needed a power source and a shutter-synchronization circuit to actually set them off. And that wasn’t always reliable. If the battery inside the camera was weak the flash may not fire, and according to Richard B. Martenson, Vice President of Consumer Sales for Sylvania Lighting Products, that resulted in over 100 million flash pictures being ruined each year.
Tragic! So, to fix this problem Sylvania, once again in partnership with Kodak, developed the Magicube and released it in 1970. I’m not entirely convinced increasing reliability was the motivation here but we’ll get back to that. The actual flashbulbs inside of here may not look very different compared to the AG-1 bulbs, but as I was telling Gav these are set off mechanically and not electrically. After very carefully removing one from an unused flashcube, we can see that a small metal tube is protruding from the base of the glass envelope rather than a couple of wires. That tube is filled with a chemical compound known as a fulminate.
What makes fulminates useful for photography is that they’re explosive. Yeah! Yeah, this little metal tube is filled with the same sort of chemical that goes into percussion caps to ignite gunpowder in firearms. I tried to figure out what specific fulminate might be in here and didn’t have too much luck, but that’s not really important. What’s important is that when you strike this tube very quickly with... something,
its contents will explode. Remember, we used these so we could take pictures at night. Now, much like a percussion cap, that explosion is used to initiate a second combustion event, though instead of gunpowder accelerating a projectile forward out the barrel of a gun, it’s zirconium shavings in an oxygen atmosphere to produce a lot of light all quick-like. Inside the flashcube, tucked neatly behind the reflectors, are four pieces of wire which form simple springs. At the base of the unit you’ll see that one end of each spring is being retained by a little metal nubbin.
Those ends of the spring are visible and accessible from below, and if I push up on one to allow it past the retaining nubbin, the tension is released and it almost instantaneously flies at the primer tube and gives it a good whack. That impact causes the friction-sensitive fulminate to ignite which in turn sets fire to the zirconium shavings and in an instant you’ve got yourself a very bright flash of light. This Kodak Instamatic X-15 is a simple camera which works with Magicubes. Simple is pretty much the name of its game: this is a purely mechanical, plastic camera with no automatic light metering or indeed exposure adjustment of any kind. Every image this takes is captured through its fixed-focus lens with an aperture of f/11 and a shutter speed of 1/90th of a second. Thanks to the generous exposure latitude of color print film that was certifiably Good Enough™ for outdoor photography in most conditions but once the sun sets or you head inside, it’ll need some help.
So, just plop on a Magicube, and say cheese! [click] How does the camera set if off? Well, if you look closely as you attach the flashcube, you’ll notice a small pokey bit coming up from just next to the socket. As you may have guessed, this is what fires the flashcube by pushing up on the spring to release it from its catch and allow it to strike the primer tube. But the actuator also serves as a check for whether the flashcube will work. Prior to taking a picture, the actuator is lifted into place with very light pressure.
With a fresh flashcube, the trip wire will prevent that actuator from moving very far up. But, if you are re-using a flashcube and insert it with a spent lamp facing forward, the actuator will make its way past the position of the spring and a little red flag indicator is lowered into the viewfinder to warn you. Pretty clever.
But, assuming the spring is still there for the actuator to… actuate, the red flag does not appear and you’re ready to take a picture. When you press down on the shutter button, the camera forces that actuator into the base of the flashcube, pushing the spring above its catch, and letting it fly into the primer tube to set off the explosive fulminate. The initiation is very fast - just four milliseconds after the shutter has opened, the flashcube begins producing light. And its output peaks just 7 milliseconds later. With a flashcube installed, the camera does slow its shutter speed to 1/45 of a second, and that's just about the perfect speed for gathering as much of the flashcube’s light onto the film as possible.
And, for the icing on the cake, when you advance the film frame using the winder on the back of the camera, the flashcube automagically rotates 90 degrees so your next shot is ready as soon as possible. There’s some delightful mechanical goodness in the actuator getting pulled down as the cube begins begins to turn. Mmm, clearance! If you’re wondering how much these things cost, well a package just like this originally retailed for $2.25. Adjust for today's money, and that’s nearly eighteen dollars! And since this is 3 cubes slash 12 flashes, that means each flash photo you took cost basically $1.50 on top of the cost of the film itself. In 1975, a 20 exposure roll of film for this camera (plus prints) cost about $5 and adjusted for inflation that’s not quite $30 which, well, works out again to about $1.50 per photograph
so using the flash back in the day just about doubled the cost of taking a single picture. Unless of course you were shooting slide film - that used to be cheaper, ya know! Now you practically gotta get a mortgage to shoot a single roll of Ektachrome. While Sylvania and Kodak claimed that they developed the Magicube for more reliable flash photography, to be honest that doesn’t smell all that truthful to me.
Kodak, although they’d happily sell you a camera, really wanted to sell you film and processing for that film and prints of those pictures on that processed film. Their cameras were the gateway drug to get you hooked on taking snapshots with their film products, and wouldn’t it be great if they could make their cheap, entry-level, flash-capable cameras even cheaper by removing the battery and wiring and junk? I’m pretty sure that was the real goal of adding explosives to the photography process. After all, the packaging on these GE flashbulbs is pretty darn confident that they’re all gonna work, and they’ll even send you four new ones if you send them a dud. Still, while it definitely seems pretty off-the-wall in hindsight, the concept did work and worked very well. And if we still needed to rely on single-use flashbulbs for cheap flash photos anyway, I suppose adding a little explosion to the mix wasn’t the most ridiculous idea.
But I think that’s enough exposition, don’t you? The absolutely bonkers way by which these are ignited is the entire reason I traveled to Austin and enlisted the help of a Slow-Mo Guy. I really want to see what this looks like in slow motion, so let’s cut to the chase. So we're about to shoot the first flashcube and I do not remember which one I poke to make that one go off. So we have a 50/50 chance that this is gonna work. Um… [Gav] At least you've narrowed it down 50/50 though and not one in four.
-Yeah I mean I really cannot tell from the mechanism which way the spring goes. I… I think it's this one but I could be wrong. We'll find out in a moment you ready? -Ready. three two one [crack] -You nailed it. That was the right one! -Hey I got it right the right
[laughter] Okay. Woah. [laughter] I think we're going to need the faster camera! -Yeah! What - you can't even tell at all what initiated that. It just looks like it exploded.
[Gav] Go frame by frame… [Alec] Well, that's very bright. But yeah we need the… we definitely need the bigger guns. [Gav] Bigger gun time? -I think so! -All right let's do it.
Okay we've whipped out the big guns cuz that didn't reveal anything so what is our frame rate? [Gav] 200,000. - 200,000 frames per second! Okay... - It's quite the leap. - Yeah! Um... let's see what happens! Here we go, I got it three two one bl-sfh, or again, three two one [crack] The footage we got here was spectacular. A plume of sparks shot out from the base of the bulb and ignited the zirconium, with the filings burning like brilliant fuses.
One spark even managed to make it beyond the midpoint of the tube, and we can see that the exact spot where it collided with the zirconium is where the zirconium itself began to burn. This is basically a firework. [Gav] Yeah! -It is a very calibrated, easy to set off firework. For the purposes of photography.
It’s propagating so slowly! [Gav] Yeah, I mean, it’s just that first bit that’s fast. I can’t believe how bright it is. Even at a one microsecond per frame exposure. This is - at your playback frame rate this is slowing one second down to 111 minutes.
[astonished laughter] A feature-length film out of one second! Oh these cameras are amazing. While we got plenty of detail of the initiation explosion, the zirconium burn was still blowing out the sensor. And remember each frame was captured over a tiny, tiny fraction of a second! These things are ridiculously bright. Gav decreased the shutter angle in the hopes of uncovering some more interesting details as the flash reached full-brightness. 3, 2, 1 [click] …so one of those Sparks runs into the zirconium. Now the tails are burning.
[Gav] So are we actually seeing the travel across each each, like, hair of it? - I think so. I don't know what what else that could be. It's like … it's like a bird's nest that you set on fire. [Gav] Yeah. So a crazy moment in time where one half of the flash has gone off. -See it's pulling the wire closer… it probably shrinks a little bit. -Lots of contractions and… yeah a lot of thermal action in there.
[Gav] See that there, that's just like globs of molten metal there. See that… see that one explode? [Alec] Oh wow! -It was like a bubble. -What‽ [laughter] [Gav] I wonder if there's air trapped in little -little bubbles of zirconium? - bubbles of molten zir - they're - they're all exploding! - That is amazing. - You can see why I wanted to switch to this camera right? Because there's, there's always like a deeper level that you just start seeing even crazier stuff.
Yeah all of these bubbles popped. [Alec] So I wonder why they're forming… Maybe oh, well I - okay so maybe as the wire is burning the center of it melts and it lets in some of the oxygen or whatever else might be in there. [Gav] And we saw the the wire contracting towards the middle so I assume as it's burning and melting it's like pulling more liquid in and just making these… It’s pulling more wire in and making orbs of glob.
OK, so obviously that was pretty cool. Lots of interesting stuff was uncovered in the high speed footage. But we also uncovered something else. I had presumed that the electrically-triggered ones just had a couple of electrodes sticking into the chaos of the zirconium foil. Run some power through there and whatever bits of zirconium are touching those electrodes will complete a circuit to the other side, it’ll got hot, and since it’s a pure oxygen atmosphere that’s gonna make it get all burny real fast. But in the 1,000 frames per second footage capture from the 4K camera, we were able to see… something.
[Gav] Was there like… do we actually see an arc? - Oh that's probably - that's a filament! So it actually is burning… [Gav] So there's a filament in there just like a… -Probably yeah just, just a little filament. And then it basically causes an explosion. [Gav] That's one frame later, so that's only like a thousandth of a second later.
-Wow so there is… I didn't think this would be that fast. That is amazing. At this point I was thinking, alright I guess it makes sense for there to be an incandescent filament in there. That would give the lamp predictable electrical characteristics if nothing else, and a bit of tungsten wire that will definitely get hot when you pass current through it is probably more reliable than just poking electrodes into a briar patch of filings. But switching to the faster camera revealed there was more to it than that.
3… 2… 1… Oh. Does the filament, like, vaporize? What's happening at the beginning? Well now I'm totally unclear on what's happening at the beginning. Maybe the… maybe the filament is like a kind of detonation cord. [Gav] Oh that's cool you can see the little streaks of smoke. Psh-owrn! [Alec] Oh there's one of the globbles.
So they seem to happen at the end. So I wonder if that's because the oxygen's getting used up and it's just a bubble of, like, oxides that's not actually burning. I'm looking at this to see if I can even see what's going on with that filament. The… the electrodes are definitely like poking up. My gut is that the filament is...
I don't know, maybe it's a piece of tungsten that's coated with an explosive compound? ‘Cause it looks like it's vaporizing. It doesn't just look like it's turning on. [Gav] Is there a way to get the glass off? -Not without just breaking it. -But would it be interesting just to break the bulb and film into the hole? Just to get the the primer going off? [Alec] We can try it, you got some safety glasses and a hammer? Okay in the interest of science… I really don't know what on Earth is going on with the filament.
I thought it was just a tungsten filament but based on that high speed it kind of looked like it exploded. So, um, I have hammer. And safety glasses! [Gav] I think you need to duck further into it. Am I visible? No, it’s - more.
There you go! [laughter] I'm wearing safety glasses, okay? And Gav's way back there, so. Actually because of the coating it's probably not… this might be difficult! -Yeah. -We’ll see… [BANG] Okay that was under pressure! That was definitely under pressure. [Gav] I heard glass hit the the ground about 20 feet away. Great where's the the f… [laughs] I don't know if we can do this! Okay we're trying this again with a bag.
[Gav] I'm going to hide again. [hammer time] Okay, it did pop right out. So that is probably somewhere in the room.
-Okay -But we got it! -I'll let you know when I find that in 2028. [Alec] I mean I really don't know if anything's going to happen here, but we can try. -Okay -You ready to go? -Ready.
In three. Two. One. [pfft] -Something happened! -Ohh, something happened! -That was big! -That was way… it's… -Oh, a smoke ring! -There’s like a smoke ring! So, it would seem even the electrically-operated flashbulbs still relied on explosives to initiate the zirconium burn. But what is that explosive? Well… I don’t know. I found references to a so-called “ignition paste” in a patent filed for an improvement to flash lamps made… way too late for it to do any good. And following that thread led me to a discussion where rhenium was coming up. I followed through on that patent the folks were discussing and it mentioned rhenium in the composition of the filament but not the ignition beads.
Ignition beads? Well, in this macro shot it does appear as though the filament was covered in little beads of something. As the filament broke, one even went flying! After a little more digging, it seems that in order to improve reliability (particularly with weak batteries) flashbulb filaments were designed to be deliberately weak in order to get hot (and therefore begin incandescence) essentially instantly. But that meant it was probably going to break before the zirconium began to burn.
Whichever bead of primer was closest to the weakest and hottest part of the filament was almost certainly going to ignite, sending a plume of incandescent sparks out amongst the zirconium. That means that there are actually four steps to this process: first, a camera sends power through the filament as its shutter opens. Then, the electrical resistance of that filament causes it to get hot to the point of incandescence in a miniscule fraction of a second. Next, the resulting heat ignites at least one of the primer beads on that filament which sends a plume of sparks out into the nest of zirconium wire.
Finally, some of those bits of burning primer collide with the fine zirconium wire, causing it to rapidly burn in the oxygen atmosphere and emit brilliant light as it does so. In the end, both styles of flashbulb rely on an explosion to reliably set the zirconium they contain alight. Sylvania’s Magicubes take a literal shotgun approach by firing sparks up through the primer tube, but now that we know the electrically-fired ones do, too, that almost seems reasonable. This footage of the larger M2B bulb firing is perhaps my favorite shot we got.
You can clearly see the distinction between the primer explosive firing and the zirconium beginning to burn - in fact, you can see what looks like a piece of filament with its primer bead igniting long after being blown clear of its original position. Then we see the wire start to ignite, and as they burn like tiny little fuses, the bright spot in the bulb propagates until all of it is ablaze, leaving nothing behind but a cloud of smoke. And remember, in real-time, that all happens this quickly. [crack] Ahh! [laughter] So, uh, what did we learn today? Mainly that it’s brighter than I even imagined. Like, at one point we had a 95 nanosecond duration which is shorter than my brain can even comprehend, and it was still blowing out the sensor.
Yeah, it was uh… a struggle to get some of these shots. And, uh, he was the one struggling, I was just touching wires together. -That’s true. Uh, we also saw, which was a big surprise to me, that the initiation fuse I guess you could say actually has some explosive charge on there. That was a surprise, I thought it was just… honestly I thought it was just putting current through some of the actual little schnerbles of wire, there. And people flew with these? Flew with them, and checked them in their bags and man.
They were commonplace. As I was saying at one point, imagine you had to pay for every frame of film. Now you want a flash? That’s an extra… I don’t know what these were, maybe 25 cents? Who knows.
Yeah, go ahead and venmo me. Ha, yeah, that’ll work. Well, thanks again to Gav for this awesome footage. I could not have made it without his assistance or definitely cameras, so. No worries, thank you very much for coming. Cheers! That was a very forced cheers, but I think we got it.
[Gav imitates TC jazz] ♫ blindingly smooth jazz ♫ See this is the problem I have in here, just like… Oh is that what we were looking for? No… is it? No, the thing we heard was… hit the ground. That’s a piece of it though, I think. I think… if this isn’t the one we set off, it… I don’t know. This might be the one that we didn’t find. Well, hi! The problem is I can’t see the top of the frame. You wanna see if your head is in frame? -Yeah.
I’ve got headroom, oh I could put my ha- oh yeah there’s plenty. I have hands! I could do that. …flash units like this often incorporated some sort of eject mechanism [rattle on the desk] [meh]… which would help you deal with the hot, spent bulb. But you’d still need to carry this and a box of… crap.
Well, I think that was a brilliant video, don't you? Sure cast a bright light on the subject. But, I dunno, you think it was a little too flashy? Might have been dazzling, even. Oh well, always gotta balance exposure. Okay that last one didn't work.
2024-02-06 14:21
