February 28, 2012

Manual Flash Made Easy

Without a doubt, one of the best features on the latest Speedlights has to be through-the-lens metering, aptly called iTTL on Nikons or E-TTL II on Canons. These flash units fire off a small pre-flash that tells the camera what the distance to the subject is and how much power is needed to get (what it thinks) is a good exposure. This is great when your distance is constantly changing, because it will calculate everything for you on the fly. But what do you do when you’re distance to your subject doesn’t change and you’ll be shooting a number of photos? If you want to get consistent results in that situation, most of the time manual flash will give you the best options. Keep this in mind, when you use manual flash, there are 4 main controls to adjust: 1 - Distance - from the light source to your subject, 2 - Power of your flash (including modifiers), 3 - Aperture and 4 - ISO.

For the most part, it makes pretty good sense why these 4 controls would affect manual flash exposure. You know that if you move your light source in closer you will get more light and you would have to change one or more of the controls - exposure, power or ISO to get a correct exposure right? Now some of you are already comfortable with off-camera flash and this tutorial wouldn’t be for you. But if you are one of those people who freeze up when thinking of adjusting those 4 controls yourself, I’m going to try to help you “make it click”.
Let me start by saying, if you don’t own an off-camera flash, I always recommend getting the best one available for your brand of camera. Granted it will cost more, but it will always pay off in the long run. Getting a speedlight that is cheaper limits you in features and its overall ability. With a Nikon it would be either the SB-800 or SB-900 or the new SB-910, and with the Canon (my own gear) it’s the 580 EX (I or II) Not only do they pump out a little more power and have some other nice features, but they also have a distance scale on the LCD panel (this will help you get consistent flash results) and we’ll need that for this tutorial. Some of you have probably wondered why that was even there in the first place?

I was recently checking out some photos that a friend of mine had taken at a small pageant / festival. The show was set on a stage inside of a local theater. Because people were in the seats all around him he couldn’t just get up and move around so he had to stay stationary and try to get the best shots he could from where he was. He already knew he couldn’t use additional lighting because the theater was filled with people and he couldn’t use bounce flash because the ceiling was about 40 ft high and black. So he attempted to use his speedlights TTL system, but he wasn’t getting consistent results. This is definitely a case where using your flash in manual mode can come to the rescue.
In this case, he knew he wanted some pretty good depth of field, around ƒ5.6 or better, and because it was fairly dark in there and he wanted to keep the quality good, he needed to use at least ISO 400 or higher. The key part of this was that he knew he was staying 20 ft. away the whole time.

Understanding Manual Flash = Distance, Power, ISO & Aperture
When trying to understand this, remember that the ISO and the Aperture are set on your camera; the Distance and Power are set on the flash unit itself.
  1. Right from the start we know we have four controls that we’re going to need to adjust. As long as you are shooting under your flash units max sync speed your shutter isn’t going to make any real difference, so we’ll set it at 1/125.
  2. We know we want some pretty good depth of field and we’ll set that at ƒ5.6.
  3. Now we’ll set our ISO at 400.
  4. Finally, we know we will be about 20 ft. away from the stage all evening.
Keep in mind our flash unit is going to be pointed straight forward all night, no bounce flash etc. Remember, you can’t tilt the flash head up or down or our distance scale disappears from the LCD screen. Now switch your flash to Manual exposure with the Mode button.
When you turn on your flash unit it will be set to whatever settings it was in the last time it was used in Manual exposure mode. Chances are it’s not set to 20 ft. We know we have to adjust the flash power to give us the distance we want, in this case, 20 ft. Remember; we just set the shutter speed, the aperture and the ISO.
On the Canon 580 EX I or II, tap the center button of that dial, and rotate the dial. (You will have to continually tap the shutter button to activate the distance readout on the back of the flash.) Now adjust the power of the flash until you get a distance reading of 20 ft.

On a Nikon SB-900, hit the button just below the ‘M’, which appears on the back of the speedlight and adjust it until you get a reading of 20 ft. Now to test it out, take a test shot of something around 20 ft. away from you. Because we’re using direct flash it won’t be the best lighting but we’re looking for consistent light. The shot will be well exposed, judging by how well you guessed the distance, and usually within a third stop or so. These little units are very accurate so if it isn’t on the money, you probably guessed the distance incorrectly.

Now at this point think about what you just did. First you set your cameras aperture and ISO then you reached the specific distance you wanted by adjusting your speedlights power setting. Try this out, change the aperture up or down and watch the distance scale change. The same thing would happen if we changed our ISO.

So what this tells us is that if we changed one of our controls (aperture / ISO / distance) we’d also have to change our flash units output to help us retain the correct exposure. Remember though, you might have to raise the ISO to get a fast enough shutter speed to control movements, but with a little practice this should become almost second nature. Try it out in different scenarios for yourself. Once you try this out a few times it will help make your speedlights more user-friendly. When you get away from using your camera’s pop-up flash and start using a larger flashgun, it gives you tons of new possibilities in lighting. I hope this helps you to better understand your equipment.
Remember, as always, keep shooting and have some fun!
© D. Gould Photography