This chapter is from the book
This chapter is from the book
This chapter is from the book
Electronic Flash Basics
In its most basic form, electronic flash provides a portable burst of light at a very quick rate. The average flash unit goes off anywhere from 1/500 of a second to a 1/35,000 of a second or faster (depending on the model and mode.) That’s enough to expose a dimly lit subject and freeze the action of a moving one. The actual intensity of the burst and its subsequent range of coverage depend on the model and its strength, yet even the most basic flash units (including those built in to the camera) provide enough power to light a subject. The actual power of a flash unit in terms of coverage and range uses a unit of measurement known as the Guide Number (see the “Guide Number” sidebar).
Obviously, a separate unit, the kind mounted on a camera, offers more features and power, and of course, a higher Guide Number. Clearly, it’s more effective than the camera’s built-in flash unit. And yet, that doesn’t necessarily make one easier to use than the other.
Flash photography has become easier over the years because you no longer need to manually calculate its output. Currently, most flash units work in conjunction with the camera’s metering system to automatically adjust the output of light (Figure 4.1). But even the integration of the two doesn’t always ensure a perfect result for a variety of reasons, which include: the direction of light coming straight toward the subject and the flash unit sharing the same axis as the lens, which occasionally leads to red eye, either because you were too close to the subject or the unit was too strong. Sometimes the best flash photography shows the least evidence that flash was used.
)
Figure 4.1 WIndee Airedale was captured using the camera’s pop-up flash before attending a formal kibble dinner.
Canon T2i • ISO 800 • 1/60 sec. • f/4 • Canon 50mm Macro lens • Pop-up flash
Advanced Flash Unit Features
The newest models of the electronic flash unit have evolved to provide the perfect complement to today’s sophisticated Digital SLR cameras. These tools have come a long way since the old days when flash exposure was independent of the camera’s automated or Through-The-Lens (TTL) functions. Back then you set the power output on your flash—perhaps after doing some math with subject distance, ISO, and Guide Number—and crossed your fingers.
But flash units have greatly improved since those very technical, yet trial-and-error based days.
Here are some of the features you’ll find on flash units now:
TTL flash metering: Whether the manufacturer calls it iTTL, eTTL, or whatever letter precedes TTL, Through-The-Lens (TTL) flash metering produces more accurate output because it measures the light in the scene directly through the lens. Early models used a sensor on the flash, which could be fooled by elements outside the frame, as shown in Figure 4.2.
Figure 4.2 The subject was in shadow under a scaffold for this portrait set against the colorful light trails of passing traffic. By setting the flash to -2 stops, I was able to make the setting appear more natural. The only giveaway is the light reflecting in the woman’s sunglasses.
Nikon N90s • ISO 100 • 4 sec. • f/8 • Nikon 35–70mm lens • Nikon SB-26 Flash
- Exposure compensation: Even with TTL, you can fine-tune flash output by increasing or decreasing output by 2–3 stops (depending on the unit). This allows you to tweak exposure more effectively, especially when combining flash with long exposure.
- AF assist beam: When you’re shooting in low-light conditions, sometimes not enough light is available to focus the scene. But now this is not a problem. Some models provide a built-in assist beam to help determine focus in dark or low-lit areas.
- Slave ability: This flash unit mode lets you trigger one or more flash units positioned in the scene based on the burst of your main flash. You can even hold the camera-mounted flash with one hand and the unit set on Slave in the other to provide fill light.
- Movable flash head: Although a movable flash head is not a new feature, it has seen some improvements. With it, you can tilt the head upward to bounce light from a surface above the scene, and some let you swivel the head to either side to reflect light from a wall. Many also include a slide-out bounce card.
- Filter holder: Regardless of the lighting conditions, flash output matches the color balance of daylight, which is 5500 K. But you can match the color temperature of ambient light by using the proper filter.
- Wireless capability: With wireless capability, you can remotely trigger one or more flash units positioned away from the camera when you press the shutter.
)
Reasons for Using Flash
Bringing light to situations that have none or very little of it is the most apparent reason for using flash. But it’s not the only one. Numerous reasons exist that range from the necessary and the practical to the scientific and the creative. Some are serious for creating the most compelling imagery, whereas others are handy for the silly snapshots, as shown in Figure 4.3.
)
Figure 4.3 If the question of what to do with a watermelon after scooping it out arises, taking a whimsical approach and carving it into a mask is one option. This melon head was captured with the pop-up flash on a DSLR.
Canon 20D • ISO 200 • 1/60 sec. • f/2.5 • Canon 50mm Macro lens • Pop-up flash
Consider the following as to when to use flash:
- Bring light to dark areas: As previously mentioned, adding light to unlit areas is the most common reason for using flash. No matter how dark the scene, as long as the flash burst reaches the distance to the subject, it can even illuminate a piece of coal in a pitch-black cave. Of course, more practical uses include exposing people in indoor situations or a stationary subject in low-light conditions.
- Stop action of a moving subject: If you want to freeze action and illuminate it at the same time with a bright burst of concentrated light, flash can do that for you too. Of course, the subject must be in range to reap the full stopping power. Also, make sure the shutter duration doesn’t exceed the flash sync speed (see the sidebar “Flash Sync Speed”).
Correct color balance: More realistically, flash provides a predictable color temperature by overpowering the existing ambient illumination. Flash produces a color temperature similar to daylight, which comes in handy when you’re shooting a subject in unflattering illumination (Figure 4.4).
Figure 4.4 This New York Giants fan celebrates his team spirit on a cool night. The artificial lighting is relatively bright, but it has a dominant reddish colorcast. Flash provides the subject with a normal color balance.
Canon T2i • ISO 1600 • 1/60 sec. • f/4 • Canon 24–105mm lens at 45mm (equivalent to 72mm) • Pop-up flash
- Create special effects: Even though you don’t always need a flash unit with sophisticated features to be creative, it does provide more options. Depending on the model you use, you can produce a variety of effects, including multi-flash, which allows you to capture the subject in various stages of motion; rear curtain synchronization, which fires the flash at the end of a long exposure as opposed to the beginning (see the section “Rear Curtain Sync”); and color filtering in which you use a holder for colored gels for correction and creative purposes.
- Mix flash with long exposure: Use flash with a long exposure to balance a portrait with the background, mix color from flash and artificial light, and paint with flash.
On-Camera Flash
It doesn’t matter if you have a pop-up flash on your DSLR, a built-in flash on a point-and-shoot camera, or whatever that burst of light coming from your smartphone is called, the direction of illumination will basically be the same. Each flash will get the job done, but it’s not always perfect. Even when you’re using a feature-rich unit mounted atop the camera, it still exposes the scene with direct illumination, and that’s not always the most flattering light. Why?
Because the flash hits the subject head on, it creates a number of issues, including harsh light, washed-out illumination, and a disparity between the areas it doesn’t reach. When the scene is rife with blown-out highlights and detail-less shadows, they create a high-contrast ratio that makes the photo lack dimension, and it’s not very appealing.
Another issue occurs when the flash is too close to the axis of the lens, which increases the possibility of red eye. Still, it’s hard to beat camera-mounted flash because it’s easy to take advantage of, especially when you want to grab a quick snapshot (Figure 4.5).
)
Figure 4.5 On-camera flash is great for snapshots, because the moment of capture can sometimes carry as much weight as the aesthetic.
Canon T2i • ISO 800 • 1/60 sec. • f/4 • Canon 24–105mm lens at 47mm (equivalent to 75mm) • Pop-up flash
Dealing with Red Eye
That possessed look of people in some pictures has plagued photographers ever since the flash unit was introduced. Red eye is not solely a problem of on-camera flash; rather, it occurs when the flash, lens, and subject’s face converge on the same axis. When that happens, light reflects from the retina in the subject’s eyes, producing those darting red pupils (Figure 4.6). Some cameras and flash units have red-eye reduction modes. You can also correct the problem in Photoshop or another image editing application.
)
Figure 4.6 The built-in flash on many cameras sits very close to the lens and will cause red eye when in line with the subject.
Nikon 5000 • ISO 100 • 1/60 sec. • f/2.8 • 28mm lens
But you can prevent red eye from occurring by trying the following techniques:
- If you’re shooting close to the subject, avoid having the subject look directly in the lens.
- Bounce the flash. (See the next section for an explanation of how to do this.)
- Use an off-camera flash.
The Effectiveness of Bounce Flash
Some camera-mounted flash units allow you to change the direction of the light source. By positioning the head away from the subject and onto an area where it can reflect and hit the subject with softer, more directional light, you’re able to use the flash mounted on your camera more effectively (Figure 4.7).
)
Figure 4.7 This classic portrait was simply illuminated by bouncing the on-camera flash off the white ceiling at a slight angle.
Canon 20D • ISO 100 • 1/60 sec. • f/8 • Canon 50mm lens (equivalent to 80mm) • Canon Speedlite 580EX Flash
Bouncing the flash greatly increases the quality of illumination from your on-camera flash by softening the light and spreading it out. Of course, this technique does have its limitations: one of which is not having a place to bounce that light. Bouncing prevents the flash from spewing the light as much as it redirects it for a more flattering rendering of the subject.
Bouncing flash off a ceiling or wall does require extra flash power, but the results are well worth it.
Consider the following bounce flash tips to bounce flash effectively:
- Tilt the flash at an angle that will effectively illuminate the subject.
- Make sure the color of the bounce surface is neutral (white is always best) because it will affect the color of the flash.
- Ensure that the bounce surface is not too far from the flash so you have enough power to bounce the light onto the subject.
- If a bounce surface is unavailable, you can choose optional flash attachments that redirect and spread the light. These include a bounce-dome diffuser that fits over the flash head; a mini softbox that attaches to the flash; and a light bouncer that redirects and softens output.
Where Do I Bounce Now?
You just have to face the fact that you won’t always have a surface to bounce the light, especially when you’re shooting outdoors. You certainly won’t be able to bounce the light from a ceiling. But you can still bounce the light using a bounce card to redirect the light from the subject. Some advanced camera models include a built-in bounce card that slides out, such as the one I used in Figure 4.8. But don’t worry if you don’t have one. You can just attach a white card to the flash using a rubber band to hold the card in place.
)
Figure 4.8 When you’re shooting outdoors, it’s hard to find a place to bounce the light. Fortunately, this flash unit had a slide-out card.
Canon 6D • ISO 100 • 1/13 sec. • f/1.8 • Canon 85mm lens • Canon Speedlite 580EX Flash
Off-Camera Flash Works Really Well
Using flash away from the camera provides a more effective means of lighting a scene. It allows you to change the direction of light to come in from the side, which is always more flattering to the subject (Figure 4.9). You can use the flash in several ways, but the most basic way involves using an accessory cable that plugs into the camera’s hot shoe and onto the flash. You can either use a bracket (a device for holding the flash off-camera) or simply handhold the flash to create beautiful lighting that may not resemble flash at all.
)
Figure 4.9 Holding the flash away from the camera allows you to produce a more flattering, dramatic illumination.
Canon F1 • ISO 200 • 1/30 sec. • f/11 • Canon 24mm lens • Vivitar 285 flash held off camera
){kind=link}