Advanced Flash Techniques
Well, there's a few other little things I wanna talk about and I'm kind of throwin' 'em all here into this Advanced Flash Techniques. As I say, flash is one of the more complicated areas of photography, and so there's a few extra special things in here that we can work with. And we're gonna talk about Slow Speed Sync. And we'd looked at this a little bit before with some of the photographs. But if you remember, the flash fires very quickly and then it's over with and that's it. And if you wanna shoot with a longer shutter speed, you can leave the shutter speed open as long as you want. And so that longer shutter speed is gonna be used for grabbing the ambient light that is already out and around there. You're using the flash to illuminate your subject, but you're often letting the ambient light in for the background. So going back to some of my running photos, you can see here at a relatively fast shutter speed, at 30th of a second, we're not getting much light in the background. And s...
o we can start playing around with different shutter speeds. Now these are not clinical tests done in the studio, these are some wild changes out here, so there are gonna be some changes here in the shutter speeds. But there was this night race that we were photographing and I wanted to show a little bit of the sunset in the background. And so using 125th of a second, I was able to balance the flash along with some light there in the background. And so having your subject sharped with a little bit of light in the background is probably a lot better than just having a background that is pure black. And so in these cases what I'm often doing is I'm figuring out what the exposure should be without any use of the flash at all, and then I will add some flash and if I didn't do it right I'll just kind of back off on the power of the flash so it's the right balance between the foreground and the background. But to start with, you can set this up as a pretty much normal landscape shot, knowing that the foreground just isn't getting illuminated enough and then you can eventually go in there and add some flash. Very old photograph at this point now, my old college roommate here having fun here in the middle of the highway, using a really long shutter speed and adding a little bit of flash to it. Now the way that flash fires is normally with synchronization of the first shutter curtain opening. So what happens is the flash fires and then you have a long shutter that is open. But you can do a Rear Curtain Flash Synchronization. And so let's take a look at what's happening at the sensor and with the shutter blades. So with the normal flash, what happens is the first curtain opens up, the flash fires, and the shutter may stay open for a little bit longer until the second one closes. That's your Normal Flash Synchronization. In Rear Curtain, first curtain will open up, your exposure will be captured by the sensor and then right before the second curtain closes is when the flash fires. And this is gonna make a big difference on any sort of subject that is moving through the frame at the time you take that picture. So this is an example of Front Curtain Synchronization. You can see where the subject is at the beginning of the shutter and then they are moving, creating this blur during the shot and then the shutter closes. And in a situation like this a Rear Shutter Curtain Sync is gonna look much more natural, and that is because a lot of us have watched a lot of cartoons. And they know when you run really fast, the streaks come out the back side of you. (audience laughs) And that's what makes it look like this, this is more natural. So thank you cartoons and thank you cameras for giving us this look. And so it's kind of a fun thing to do and if you do have anything that moves, it could be argued that it should be set on Rear Curtain Sync all the time. And so there's not really a lot of downsides to a Rear Curtain Sync and so it's perfectly fine to leave it there all the time. It does work out in many other situations quite well. All right, another one is High Speed Sync. Now if you're doing portrait photography, we've talked about some portrait photography before and we talked about shooting with a really shallow depth of field. Well if you wanna add some nice light, well what happens? Well, I am shooting at 125th of a second, f/11, on a bright sunny day, well I would like shallower depth of field, what can I do? Well I can stop down to 250th at f/ but I can't go any further than that because my camera's maximum synchronization is 1/250th of a second. If I set it to 500 or 1000 or anything faster, we get that shot that has a little strip of area that's illuminated and everything else is dark and that's because the shutter has to leave the entire sensor available for that flash to fire during that period of time. So manufacturers have thought about this and they've come up with a work-around. It's not a perfect solution, but it is a work-around. So remember normally, first curtain opens, flash fires, second curtain closes. Flash has to be able to see the entire sensor 'cause it fires in one single burst. At a high shutter speed there is a scanning system where if the flash fires it's only gonna fire and it's gonna only illuminate a portion of the frame. So you can't shoot at high shutter speeds like a 1000th of a second. And so there is a High Speed Flash Synchronization mode on some flashes, it's not all flashes, it's some typically higher end ones. And what it does, is it fires the flash a whole bunch of times, so that it's a roughly an equal amount of flashes for each little pixel that happens to be exposed to light. And so if we were to chart this, we've said a normal flash is one big powerful flash and then nothing. And what this high speed flash looks like, if we were to measure it in a very short period of time, like a 1000th of a second, this is a normal flash, one big power stroke you might say, and the high speed sync looks like this. It's a bunch of small little bursts. It's like a strobe light going on and off, and so it fires really, really quickly. It happens so fast that to our eyes it looks like just one continuous burst of light. But in actuality, it's gonna be a bunch of low bursts of light. And so now I can go up to 500th of a second, I can go up to a 1000th of a second and shoot all the way down at 1. and get shallow depth of field. The downside to this is because of the system firing so many flashes, it can't work in a TTL fashion. It has to be in a manual fashion, which is the one limitation. Which that one's not too big. I can work around manual flash. Manual flash is fine. The real problem is, is that it has a highly limited distance. Because it's firing low powered flashes, it's like at 1/10th power and you really gotta get your flashes in quite close or you have to have a pretty high powered flash in order to do this. And so this is something that you will get with the Speedlites from Nikon, Canon, and many other manufacturers as well. Another specialized technique I'll use once in a while is a Multi Strobe technique, which is firing the flash a number of times during the exposure. Now there's a lot of creative options here. I'm just gonna show you a couple of photos. And so I was doing some caving with a friend and I had him walk down this one path and had him just fire the flash about every 15 feet. And just fire it up against the wall and I'll get a silhouette of you walking along this path. And so this is all just completely manual. I put my camera into the Bulb mode, left it open for about 30 seconds while he walked along here. With another friend, I wanted to analyze his running stride. And so I set out a bunch of flashes to fire all in harmony with each other, and I wanted to try to get as dark a background as possible and at least something else in the background as well as there. And so what this really looked like from a different angle of view is I have multiple flashes out there to help cover the wide scene, 'cause it was tough to get one flash to light that entire scene up. Another friend gettin' a little crazy here at the campfire. But firing the flash, and you have to play around with the settings on this and this is firing at probably about five frames per second as he quickly runs and jumps over the fire there, and so you can see all the different sequences. And so there's a lot of fun that you can do with these specialized modes there. And so flash photography is an area of great exploration, and so I encourage you to get your flashes out and see what you can do, 'cause there's a lot of ways to play with your photography there.