I’ve had a lot of photogs ask me how I get these nicely balanced outdoor shots by mixing eTTL flash and bright sunlight. It’s equal parts technique and technology. The technology exists in your Canon or Nikon camera and flash combo — it’s called HSS or High Speed Sync. But before I cover HSS, let’s talk about how your speedlite and camera work together in general. As most of us know, there is a maximum flash sync speed for each camera (often call the X speed). It’s the fastest shutter speed that we can set our camera to and still have the shutter sync up it’s timing to the burst of the flash. For most cameras, it is 1/250th. Nikons often will sync at 1/500th, but the key is to know what your X speed is for YOUR camera. Look it up if you don’t know. Do it now…I’ll wait… Got it? Good. But what happens if we set our shutter speed to be faster than this X speed? You will start to get a black bar on the edge of your frame. This is the edge of the shutter curtain as it travels across your focal plane in front of your sensor. The higher you set that shutter speed above the X speed, the worse the black bar becomes. But what happens if you set your shutter speed slower than your X speed? Nothing, when it comes to your flash exposure. However, the slower you set your shutter speed (when using flash) the more the ambient light will affect your shot. [This is an entirely different lesson, so I won’t go into detail here. If you want to learn more about this, come to my seminar or buy my Flash Fu book when it comes out. 🙂 ]
Wait a minute….if you are saying that your X speed is 1/250th to work with a speedlite, how are you successfully using shutter speeds as fast as 1/8000th with flash? I don’t get it!
The secret, grasshopper, is this mysterious HSS feature. You can turn on HSS on the back of your Canon Speedlite by pressing the button next to the H with a lightning bolt. That enables HSS. What does that mean? I’ll tell you. With HSS enabled, your camera and flash kick into superhero mode. The camera and flash talk back and forth very quickly, communicating about the scene and the exposure. In a shot like the one I show here, the camera will say to the flash, “Hey, this dude wants to shoot wide open in Av mode. I’ve got to set the shutter speed to 1/400oth or else this jerk is going to blow out the sky. Oh, and get this, he just told me to dial down the exposure compensation by ONE STOP. Holy crap — that means 1/8000th! What are we going to do?” The flash says, “Dude…chill. Got it covered. I’m like all HSS and stuff. I’m going to send out this micro burst of flashes that will totally time out with the little gap in the shutter curtain as it zips across the focal plane, bro. It’s all good — he even dialed up the flash exposure compensation on my back to +3 stops, so we totally have this one covered.”
I paraphrased the conversation, but you get the idea. The flash adjusts its output to time with the little opening between the first and second curtains of the shutter so that your exposure is evenly illuminated. However, it important to understand that this takes a ton of power to accomplish this feat, so know this: the effective power of your flash will be knocked down considerably. How do you compensate? Get the flash as close to the subject as possible. My rough guideline is that in the scene that I described above, I want the flash no more than 10 feet from the subject, and closer if possible. It will also help to have an external battery pack attached to your flash to help with the power needs.
So how am I triggering the flash? First know that you can use an on-camera flash and the technique I described above. The downside, obviously, is flat lighting. So I try to use off-camera flash whenever possible because it allows me to dictate the dimension in the photograph. There are three ways that you can fire an off-camera flash while maintaining the eTTL communication between the camera and the flash:
- Use two dedicated speedlites in IR communication. One is set to Master (and is the one on the camera) and the other is set to SLAVE (and is off-camera). Be sure that each flash is set to the same Channel — Canon speedlites have four channels to choose from. The Master flash could be pointed at the subject as fill, or eliminated from affecting the scene by pointing it straight up or to the side (to piss off any bystanders) or by telling it not to fire via a custom function (look up the specific custom function in your flash manual).
- Use an IR transmitter, such as the Canon ST-E2, and one speedlite in IR communication. The speedlite would be set to SLAVE and used off-camera. The transmitter’s sole job is to communicate the eTTL info back and forth from the camera to the flash.
- Use either of the methods above with the addition of a RadioPopper or PocketWizard Flex transmitter/receiver system. These systems take the wireless IR signal and turn it into dependable radio signals that will be affective from as far as 200 feet away (RP) or as far as 10 feet (PW) — okay, I’m just kidding about the PW system (sort of). The IR systems built into the flash and IR transmitter are a bit undependable. It’s like your TV remote; sometimes it works fine, sometimes you have to bounce it off the Velvet Elvis on the wall to get it to talk to your TV. The same problem occurs with the flash IR. That’s why I have moved to a RadioPopper system — it is much more dependable, and dependable, repeatable results are hugely important to a professional photographer. Plus with a RP system, I can place a speedlite inside a softbox or behind me — it no longer works on a line of sight system.
That’s some of the technology being used to create these images you have been seeing. Let’s get back to technique. Because your aperture primarily affects the flash exposure (again, another lesson that I won’t cover here), I have found that I need to shoot as wide open as possible to help the flash out a bit as it battles strong ambient light. That’s why you see settings like 1/8000th @ f2.8, or 1/1600th @ f4, or the like. The last technique that is common to many of these shots is how I process them. First, I set a primary adjustment to the RAW file in Lightroom. Then, I tweak it using Nik Viveza2 in Lightroom. Viveza2 allows me to selectively adjust brightness, contrast, saturation, and structure based on color or tonal selections in the image. It is MUCH faster to use Viveza2 than it is to do selective adjustments using LR alone. Finally, for shots that need more tactile punch, I hit them with Tonal Contrast in Nik Color Efex Pro in either LR or in Photoshop.
To sum up:
- Know your X speed.
- To exceed your X speed, you will need to turn on HSS in your flash.
- You can use eTTL wirelessly via the IR system built into your flashes.
- You will need a Master flash or a dedicated IR transmitter on your camera in order to communicate the eTTL info to an off-camera flash.
- The new RadioPopper and PocketWizard Flex systems turn the IR signal into radio signals that will expand the reach and dependability of your wireless eTTL communications.
- A high enough shutter speed will knock down any amount of ambient light — even full sun.
- A wide open or nearly wide open aperture is key to helping your flash affect a brightly lit ambient scene.
That’s the secret. 🙂 And here is one last Flash Fu shot for a soccer team poster. The exposure was 1/1600th @ f4.5, ISO 400. Any guess on how many speedlites were used? Anyone? Bueller?