Saving the World One Pixel at a Time

1/200 sec at f/7.1 and ISO 200

Portraits are all about light, so you should begin the process of creating great outdoor portraits—including glamour photography—by looking for locations where there’s plenty of natural light but I’d also suggest that you bring along your electronic flash. Even the small pop-up flashes that are built into most digital SLRs can perk up your outdoor portraiture. The key to improving your outdoor portraits is knowing when it’s the right time to use flash.

Start by looking at the existing light falling on your subject and evaluating the range of shadows and highlights that appear within the scene. Learning to see light is not difficult but takes practice and using the SLR’s LCD preview screen will help you analyze your outdoor flash photographs to see if your efforts are successful. My guess is that with a little experience your answer about when to use flash outdoors will be “most of the time.”

All of the ingredients necessary for making great outdoor portraits are easy to find: All you need is a subject, a camera, and some light but like any good recipe it’s how all these elements are combines that goes into cooking up a delicious portrait. Just like Emeril’s secret ingredient Essence, I’d like you to add your own special spice to the outdoor portrait—flash.

When there’s plenty of ambient light as your main light source, the best way to use your on-camera flash is as fill. This helps separates your subject from the background and focuses the viewer’s attention on the subject. In fact, when you have too much ambient light using flash lets you control contrast and add dimension to the photograph.

Tip: When In Doubt, Use Flash!

Much as a digital camera’s resolution is measured in megapixels, flash output is often measured in Watt-Seconds, a unit of electrical energy that’s equal to the work done when a current of one ampere passes through a resistance of one ohm for one second. Sometimes also called a Joule it’s basically a way to measure the power and discharge capacity of an electronic flash’s power supply. Think raw automobile horsepower but because Watt-Seconds doesn’t consider the reflector design it’s not a perfect indication of the total amount of light that can be produced by an electronic flash. Because of that fact, you will occasionally see Effective Watt Seconds used a method of power measurement to give you some a use an idea of what to expect from the flash unit.

Another method of measurement is the lumensecond. The amount of light when a flash is fired can be specified in lumenseconds. A Lumen is a unit of measurement of light intensity falling on a surface. A lumensecond refers to a light of one Lumen for a one second or the equivalent, such as two Lumens for half a second. The number of lumenseconds produced by a particular flash system depends on how effectively the flash turns electrical energy into light energy or Watt Seconds into lumenseconds. Most electronic flash units produce between 15 to 50 lumenseconds per Watt Second. What all this means is that sometime an efficient 300 Watt Second system may produce as much actual light energy as an inefficient system rated at 1000-Watt Seconds.

Some people prefer to use Guide Number (GN) as a measurement of flash output because it, more of less, considers the entire lighting package. Guide Numbers are quoted in feet or meters (depending on where you live in the world) and are valid for a given ISO setting. The higher the guide number, the more the light output. Guide numbers can also serve as a way to calculate aperture when shooting without a flash meter. To determine the correct aperture, you divide the guide number by the distance from the flash—not the camera—to the subject.

All light behaves in accordance with the Inverse Square Rule that states that light’s intensity decreases by the square of the distance from the subject or more simply that light gradually falls off if the light source is far from the subject and rapidly if the light source is close to the subject. You don’t have to be Stephen Hawking to figure out that this can have an impact on the quality of light too.

The key to using your camera’s built-in flash is knowing the right time to use it. If there’s any secret at all to knowing when, it’s learning how to see the light falling on your subject, especially the range of shadows and highlights within the scene. Learning to see light is not difficult but takes a bit of practice and using your camera’s preview screen will help you instantly analyze those flash photographs to see how successful your efforts are—or not.

Using a camera’s built-in flash as the sole source of lighting for indoor people pictures will always produce some kind of a portrait but the lighting may be harsh and a bit contrasty. Nevertheless the small pop-up flashes found in digital SLRs do a surprisingly good job in delivering well-exposed pictures if you don’t exceed the maximum flash distance. Here are a few ways to solve that problem.

To avoid the dreaded “flash-on-camera” look with a built-in flash, I use LumiQuest’s Soft Screen that’s specifically designed for the built-in pop-up flashes that are found on many digital SLRs.  It not only diffuses the light from your pop up flash but can prevent red eye! It’s quick and convenient to put on and remove and softens hard shadows and reduces hot spots. Light loss is about 2/3 of a stop and the Soft Screen costs less that twelve bucks!

Another way to use your built-in flash indoors is when there’s plenty of ambient light to serve as fill. This separates your subject from the background and focuses the viewer’s attention on the subject. In fact when you have too much indoor ambient light, flash is the best way to control contrast and add dimension to the photograph.

Electronic flash output is often measured in Watt-seconds (Ws,) a unit of electrical energy that’s equal to the work done when a current of one ampere passes through a resistance of one ohm for one second. Sometimes also called a Joule it’s basically a way to measure the power and discharge capacity of an electronic flash’s power supply. Think raw automobile horsepower but because Watt-seconds doesn’t consider reflector design it’s not a perfect indication of the total amount of light that can be produced by an electronic flash. Because of that, you’ll occasionally see Effective Watt-seconds used to give you some idea of what to expect from the flash.

This lighting setup places a Multiblitx Profilux monolights behind the model at about 45 degrees. A Profilux 500 is at camera left; the Profilux 250 (even though you can’t see it) is at camera right. You can’t see it because a reflector is blocking it from view and only the light from the 32-inch round reflector is bounced back to the model. An Adorama Belle Drape muslin background is used and is held with two Home Depot clips to add some—what else—drape to the material. © 2012 Joe Farace

Another method of measurement is lumensecond, a unit of measurement of light intensity falling on a surface. A lumensecond refers to the light of one Lumen for a one second or the equivalent, such as two Lumens for half a second. The number of lumenseconds produced by a particular flash system depends on how effectively the flash turns electrical energy into energy or Watt-seconds into lumenseconds. Most electronic flash units produce between 15 to 50 lumenseconds per Watt-second. What this means is that sometime an efficient 300 Watt-second system can produce as much light energy as an inefficient system that’s rated at 1000 Watt-seconds.

Some people prefer to use Guide Number (GN) as a measurement of flash output because it considers the entire lighting package. Guide Numbers are quoted in feet or meters (depending on where you live in the world) and are valid at a given ISO setting. The higher the guide number, the more the light output.

The key part of determining any flash exposure is the lens’ aperture but shutter speed plays an important role too. The duration of electronic flash units is quite short— 1/1000th of a second is not uncommon. The exposure is made while the shutter is open but the actual shutter speed will be slower because there is a maximum synchronization speed that varies with each camera and is the time when the shutter open, the flash fires, and the shutter closes. What happens when you shoot at a higher shutter speed than your flash will synch? You get just part of a picture! What part is missing depends on which way the shutter travels and how much you get—if anything—is determined by the shutter speed. Nowadays, many cameras have a high-speed synch mode that works with specific speedlights. Check your users’ manual and see if your camera offers this feature.

Caption: The above portrait was made with a Pentax 6×7 and 75 f/4.5 SMC lens. Flash exposure was 1/60 sec at f/11 but clearly I needed to shoot it at the 6×7’s correct synch speed of 1/30 sec

On the other hand, slower shutter speeds allow more of the ambient light to influence the overall exposure, mostly the background because the aperture you select determines the main subject’s exposure. Using a slow shutter speed can open up the background allowing more ambient light to affect the exposure and show more separation between subject and backdrop. But beware the color temperature of any artificial lights that are part of that ambient light. Depending on how bright they may be using slower shutter speeds can add colors that can pollute the skin tones in your shot. The solution? Increase shutter speed but not too much! On the other hand, warmer light sources can add a pleasant warmth to the photographs with makes the camera’s LCD preview screen your new best friend.