What to look for in a flash

There are a couple of things to keep in mind when considering on-camera flash units

LIGHTING THE WAY

Understand The Fundamentals Of Flash To Make The Best Purchasing Decision

When it comes to flash, it’s easy to consign its use for night when there isn’t enough light. The real power of flash lies in its ability to improve the quality of almost any photograph, however, whether shot at twilight or midday. More than just a source of illumination when light is lacking, it’s a phenomenal tool for affecting exposure, contrast and colour.

This has become all the more possible with the technological advances made by camera and flash manufacturers. A flash isn’t an afterthought, but instead an integral part of a complete exposure system. In the case of the Nikon D70, for example, distance information from an AF Nikkor lens combines with the camera’s 1,005-sensor meter and pre-flash data from the SB-800 AF Speedlight to produce an accurate exposure. The wonder is that all of this happens by just turning on the flash.

Supplementing your camera with an auxiliary flash expands your creative possibilities. By understanding the difference such a tool can make in your photographs, the easier it becomes to choose the flash that best suits your needs.

Built-In Vs. Auxiliary Flash

A built-in flash can be the ultimate convenience; simply activate the flash and take your picture. Despite their small size, they can illuminate an area up to approximately 12 to 15 feet at ISO 100, more than enough for most shooting situations. Built-in flash doesn’t offer enough power for more distant subjects, however.

A flash’s power rating comes in the form of a guide number (GN). The number doesn’t reflect how far the flash will reach, but rather helps to calculate that distance. The formula (GN/ƒ-stop = distance) used to be a photographic "must-know" because flash exposures had to be calculated manually. Now the camera handles it automatically. An average built-in flash has a GN of around 43.

When comparing guide numbers of auxiliary flash units, it’s important to note the flash’s zoom setting. Some manufacturers figure the guide number with the zoom at a normal lens setting while others use a higher zoom position. For example, the Sunpak PZ40X has a GN of 105 at a zoom setting of 50mm, while the Sigma EF 500 DG Super sports a GN of 165 at a zoom setting of 105mm. Both units are quite capable of delivering light to a subject more than 30 feet away. So when comparing flash units, check the zoom setting to ensure a fair comparison.

In addition to offering more power, some models may include the ability to rotate and bounce the flash and greater coverage for ultra-wide-angle lenses. They also may feature wireless capability, high-speed sync and stroboscopic modes

The Fill-Flash Difference

We know instinctively to turn on the flash at night, but we may not consider its use under bright, sunny conditions. Flash in daylight can improve the quality of a photograph by reducing contrast and bringing out details and colour.

Don’t worry about overwhelming a subject with flash because it’s significantly less powerful than the dominant light source, the sun. By choosing a TTL-compatible flash, the camera calculates and adjusts ambient exposure and the output of the flash to achieve a balanced fill-flash photograph.

In a portrait of a person wearing a wide-brimmed hat at noon, for example, harsh shadows appear beneath the hat, obscuring facial details. By using a flash, light reveals colour and the details of a subject’s face. Even a backlit scene that typically results in a silhouette is enhanced to reveal subject details by turning on the flash.

Flash-Exposure Compensation

While the automatic capabilities of today’s cameras deliver excellent results, we may prefer a specific look in an image. This is achieved by using the flash-exposure compensation tool, which can be found built in to the camera or on the flash. It allows you to increase output by up to one full stop or reduce it by as much as three stops in increments of one-third.

This ability allows you to reduce the flash output and make the result appear more subtle. If shooting portraits, you might increase it slightly to reduce the appearance of distracting blemishes.

Bounce And Off-Camera Flash

The look of straight-on flash can appear flat and harsh, which is why many photographers often choose to bounce the flash or diffuse it through an umbrella. Both techniques soften the light by spreading the illumination over a wider area. Although reducing the effective range of the flash, the difference in the quality of the light often is more appealing for many subjects, particularly people.

Bouncing is done by rotating or tilting the flash head toward a white surface, such as a wall or reflector. It’s important to make sure that the surface has no colour cast, as that colour will impact your final image. A unique feature is included with the Metz 54 MZ-4 flash; a secondary flash in its body provides fill light when the main head is bounced.

You also can remove flash completely from the camera either using a dedicated TTL cord or using a wireless system. The flash then can be positioned virtually anywhere. Many high-end TTL flashes also will maintain full functionality while off-camera.

Flash Accessories

You can supplement the capabilities of your flash with a variety of easy-to-use accessories. The LumiQuest UltraSoft diffuses light produced by your flash. It enlarges and redirects the flash at a 90-degree angle and softens the light by passing it through a frosted diffuser. This reduces the harshness of shadows and delivers a softer, more pleasing look.

Even if you’re using only one flash, the Photoflex LiteDisc provides studio-like control of your lighting. Position the flash on one side of your subject and place the collapsible disc on the opposite side to create a pleasing fill-light. The circular models are available in sizes from 12 inches to 52 inches, with dual reflective surfaces including soft/gold, gold/silver and silver/white.

The Quantum Turbo Compact battery ensures that your flash has power when it’s needed. The powerful rechargeable battery supplies consistent and reliable power to your flash along with a fast recycling time. The compact battery includes easily readable LEDs for quickly checking battery capacity.

Wireless Controls

We used to be limited to how far off-camera we could use a flash by the length of a cable. Now, we can achieve distances of more than 30 feet, as well as use multiple flash simultaneously.

Unlike studio packs that are heavier and more costly, portable flash units offer incredible convenience and portability (although they don’t provide as much power). As many systems now offer TTL capability, the difficulties of handling exposure are eliminated. The output of the flash is controlled via the camera or the individual flash unit.

Creating a multiple flash setup in this way allows you to create a portable studio virtually anywhere with the results immediately displayed on your digital camera’s LCD. This displayed image provides immediate feedback on the placement and output of each of the flash units, giving you information that you can use to make any necessary adjustment.

Even non-dedicated (non-TTL) slave flash can be used, such as the Nissin Digislave or Phoenix D91-BZS. They’re an affordable alternative for achieving a multiple-flash setup.

High-Speed Sync

The top flash sync of a camera has typically ranged from 1⁄125 to 1⁄250 sec. A few models even provide a flash sync as high as 1⁄500 sec. This is the top shutter speed that ensures that the flash illuminates the entire image sensor. Too fast of a shutter speed results in the shutter partially obstructing the CCD at the moment of exposure.

High-speed sync allows shutter speeds as high as 1⁄8,000 sec., a great benefit when you want to perform fill-flash under bright conditions. When using flash under such lighting, the background is commonly overexposed, because with normal flash sync, the shutter speed would be no higher than 1⁄250 sec. To avoid overexposure, the lens might need to be stopped down to its minimum aperture, ƒ/22, for example. You may not always want to use such a small aperture, however.

High-speed sync allows the use of higher shutter speeds by emitting light in the form of rapidly repeating flash bursts barely perceptible to the human eye. Although the effective range of the flash is reduced, it provides the means to use fill-flash and wider apertures under bright conditions.

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The bottom line is that whether it’s using its built-in or auxiliary flash, today’s cameras have made getting good flash exposures incredibly easy. Simply turn it on.

A Flash In The Night

Flash Fundamentals

To make the most of your flash, it’s best to understand how a flash exposure is achieved in a TTL system. In traditional TTL systems, the flash is discharged and the light reflected off the subject returns to the camera through the lens and hits a sensor within the camera body. Based on the ISO sensitivity, the camera quenches the flash as soon as it has determined that sufficient light has hit the subject, all of this occurring within thousandths of a second.

For even more precise flash exposures, many of today’s cameras utilize a series of pre-flashes which, when combined with the subject’s distance from the camera, create an accurate flash exposure. The distance data provided by the lens-focusing system, along with the low-powered pre-flashes, compensate for subjects that are very dark or very light. Because the camera’s software knows what a normal flash output would be at a given distance for a neutral subject, extremes such as white or black subjects that reflect dramatically more or less light, respectively, can be adjusted for. Since most of this is handled invisibly, you don’t have to worry much about it. The only thing that’s important when using an auxiliary flash unit is to make sure that it’s set for TTL mode.

Improving Background Exposure

If you’ve been shooting images for any period of time, you know what a standard flash photograph looks like: bright foreground and dark background. There’s nothing bad about this; often, it’s all that you need for photographs taken at an event like a birthday party or an awards ceremony. Yet to reveal more of your background, you don’t need a more powerful flash, but rather a slower shutter speed.

This is because the flash exposure is only affected by the aperture when the camera is set for the sync speed or slower. Due to the incredibly short duration of the flash, a shutter speed that’s comparatively much slower will have no impact on the accuracy of the flash exposure. By choosing a wider aperture, however, you’ll increase the effective range of your flash. But if you want to get an accurate exposure for a cityscape, your flash won’t be powerful enough.

Instead, choose a slower shutter speed so that your camera registers more of the ambient light. The easiest way to do this is to select the Slow Sync flash or Night flash mode. Often represented by a lightning bolt symbol and the word "slow," the camera automatically chooses a slower shutter speed to register the ambient light. The result is a balanced image with a good flash exposure and a well-detailed background.

Rear Curtain Sync

Similar to Slow Sync, Rear Curtain Sync takes advantage of shutter speeds that are slower than the flash sync speed. The difference is that the flash is fired at the end of the shutter duration rather than at the beginning. The difference is readily apparent when shooting moving subjects.

A standard flash exposure with a moving subject will result in a photo where the subject is frozen by the flash, but a streak will appear where the subject continued moving into the frame, usually making the blur appear unnaturally in front of the subject. Rear Sync delays the firing of the flash until the end, which results in the streak appearing more naturally behind the subject. This can produce striking images, especially when panning, resulting in bright, backgrounds full of almost surreal hues.

With either sync mode, you can handhold the camera, but if you wish to render the background with full detail and sharpness, use a tripod. Handholding can give wild, edgy effects, but they aren’t for everyone.

Flash Exposure Compensation

Even with TTL flash metering producing accurate flash exposure, it still may not result in an image you want. If you have a preference for a more subtle or more pronounced flash look, either can be achieved easily by using the flash exposure compensation mode. By reducing the flash output, you can make a more subtle flash look. By overexposing the flash, you create a fashion-style look, where skin tones can be slightly overexposed, reducing the appearance of blemishes. The flash compensation mode allows you to increase or decrease the output of the flash in as small as one-third increments by as much as ±2 ƒ-stops.

Again, you’re only increasing or decreasing the duration of the flash. So if the flash has already reached its maximum output, this feature won’t produce anymore light (this would be better achieved by decreasing the distance between the flash and your subject).

Off-Camera Flash

One of the most dramatic ways of making your night-time flash images look distinctive is by taking the flash off the camera. Whether it’s tethered to your camera by a dedicated cable or a wireless slave system, the off-camera flash gives directional light that illuminates subjects in ways that reveal depth, rather than the flat look that’s common with most flash photographs.

Position the flash at an angle, either handheld or mounted on a light stand, and it can produce a sidelight that allows the opposing side to fall into the shadow, creating a sense of depth.

It’s also an effective way of eliminating shadows on the background created by the subject when the flash is coming directly from the camera’s position. By situating the flash higher than the camera, the shadow will be cast lower, behind the subject, and won’t likely appear in the final photograph.

Bounced And Diffused Flash

Another way to change the quality of the light emitted by the flash is by bouncing or diffusing the light. For example, by using a diffuser over the flash head, you can soften the appearance of the light when working with close-up subjects. The harsh look of flash can be markedly reduced.

Bouncing the flash into an umbrella, a white ceiling or a wall emits a diffused source of illumination. When bounced off a reflective surface, the light is diffused and produces a softer, more even illumination, which can be particularly flattering for portrait subjects. However, the diffusion that improves the quality of the light also reduces its effective range, so your subject may need to be closer to the reflective surface than it might have been if you had used the flash straight on. Also, be careful that the wall isn’t tinted, as that will produce a colour cast in your final image. When utilized off-camera, the flash can be directed to bounce more easily off some surfaces, providing you much greater control.

As you experiment with each of these techniques, you’ll discover the variety of ways flash can produce distinctive looks in your night-time images. Especially when used in combination with each other, these techniques will result in unique and outstanding photographs.

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There's no reason to use a flash unless you're shooting in the dark, right? Wrong. Outdoor photographers who can harmoniously blend their flash with any level of ambient light create more great shot situations--whether they're shooting landscapes, wildlife, sports or portraits. In the past, this process involved lots of mathematic calculations. But now, thanks to "smart" flash units, photographers are free to think creatively.

Many SLRs have a built-in flash that pops up automatically or on command. While you can't take these flashes off the camera, they're great for fill-flash and multiple-flash situations. In comparison, accessory flashes offer more power and increased range than their built-in cousins. They raise the light source farther from the lens axis, which reduces red-eye. They often provide more advanced features and accept accessories to modify the light output, too. They run off their own strong power supply, so they don't drain the camera's battery, and deliver faster recycle times, greater output and longer life. Auxiliary power packs can often be used to increase these capabilities as well.

Most accessory flashes mount into the hot shoe on top of the camera. Bracket-mounted flashes (nicknamed "potato mashers" because of their shape) are attached via a side bracket and a sync cord. These bulky units are beyond the scope of this article, although they share many of the features of hot-shoe flashes.

One of the few systems for rating flash units is the guide number (GN). This is simply an industry standard for comparing the output of one flash unit to another, rated in terms of effective distance at ISO 100. (Be careful to note if the GN is listed in feet or meters, and make the appropriate mathematical conversion if they differ.) The higher the number, the stronger the flash. Beyond guide numbers, flashes vary immensely in their abilities and options.

What To Look For
You'd be hard-pressed to find an all-manual flash these days (one that requires you to select the ISO of your film, the aperture to which your lens is set and the distance from your subject). The simplest flash units use an active system of bounced light to determine how far away the subject is and how much light is falling on it. The best are dedicated to your individual camera, meaning the computer in the camera talks to the computer in the flash. Some flash units link into the camera's exposure and focusing systems, and flash output is monitored through-the-lens (TTL).

Sophisticated systems use the AF system to determine not only the distance of the subject, but its reflectivity. (If the camera tells the flash that the subject is 15 feet away, it can determine reflectivity because a black, grey, white or metallic subject will each reflect different amounts of light.)

Additionally, a camera with sophisticated multiple metering sensors will link the AF sensor that's locked on the subject to the appropriate metering sensor for accurate output. It can even make judgment calls about ambient light on the subject.

TTL systems are especially helpful when bouncing your flash off the ceiling or using an attached accessory reflector card or softbox-style diffuser. Bounced light is softer and often more pleasing with human and animal portraits. The act of bouncing the light results in some light loss, however, and it's most accurate to have the camera monitor how much.

If you want more manual control, better units offer ±TTL settings so you can adjust your flash in conjunction with the ambient light for subtle effects and still maintain automated flash exposure. Full manual control is often available, as well. This can make the flash especially versatile if you want to use it on an older or non-dedicated camera. The guide number is also useful in calculating manual exposures.

Automatic flash-bracketing works in a similar fashion to auto-exposure bracketing. You can automatically fire a burst of three images at different flash output levels, as quickly as the flash can recharge.

Automatic zooming of the flash is a great feature. For starters, it optimizes the flash's power by changing the angle of its coverage--not unlike how the choke on a shotgun affects the shot's spread. There's no point in putting out a wide beam of light if you're using a 105mm lens because much of the light will be wasted by illuminating objects that you can't see in the viewfinder.

By directing the light into a narrower beam, more of it will be used for the subject. Conversely, too narrow a beam when using a wide-angle lens will create a hot spot in the centre of your frame. Some flashes have a flip-down diffuser for use with wider-angle lenses, too.

High-Tech Features
Off-camera multiple flash capability is an advanced function, formerly reserved for studio-style strobes. In fact, accessory flashes can now be used to bring studio lighting to on-location subjects. In systems capable of multiple flash, one flash (or a transmitter) is mounted on the camera as the controlling unit. This flash/transmitter then communicates with additional flashes that are placed as main light, fill lights, hair light and background light. The additional units are "slaved" to the on-camera unit, so they all fire on command. Sophisticated systems let you adjust the output of each unit relative to the main exposure (fill-light being less exposure than the main light, etc.).

In the old days, you had to use slow shutter speeds (1/60 to 1/250 sec.) in order for the flash to record properly on most cameras. This was because the focal plane shutter (the most common shutter on SLR cameras) wasn't fully open at the same time at fast shutter speeds. High-end flashes now offer synchronization at any shutter speed. This is an extremely important creative leap, especially in the realm of fill-flash. For example, if you want a blurred background (wide aperture) on an outdoor subject, you can now select a fast shutter speed that enables you to use f/2.8 with slow films.

You can also combine a fast shutter speed with fill-flash to create an outstanding picture of a backlit action subject.

If you want to capture the blurred movement of a subject (such as an Olympic runner with a torch) combined with flash illumination, traditional flash doesn't work well. The flash fires at the start of the exposure and then the film records the moving ambient lights during the remainder of the picture. Unfortunately, the athlete would look as if he or she was running backward in the picture. (Photographers from way back may remember comical shoots in which the model was asked to run in reverse so he or she would look right on film!) Cameras and flash units capable of rear-curtain sync solve this problem by firing at the end of the exposure instead.

Stroboscopic effects can be fun, too. They can be done manually with any camera capable of multiple exposures by placing the subject against a black background and shooting multiple exposures, each illuminated by the flash.

Because the background is black, you'll end up with multiple pictures on one frame. Some flashes make it far simpler by delivering multiple timed flashes during one exposure. This allows you to record fast action stroboscopically, such as a full golf swing or a dancer's motion.

Macro flash units are specialized for close-up subjects. If you use your normal hot-shoe-mounted flash on a very close subject, the light will probably miss the subject. Special brackets can be used to reposition your flash for macro work, assuming your flash can produce a low enough light output for such a close subject. The most common specialty macro flash is the ring flash, which provides flat lighting on close subjects. The "shadowless" light results from illumination that comes from a flash unit which encircles the lens and delivers light from all directions.

Flash Families
Canon's flagship flash unit is the 580EX Speedlite, which offers evaluative TTL flash that's intimately linked to the EOS autofocusing and metering systems and new features to improve digital EOS SLR flash results. An unlimited number of 580X units can be slaved together (in up to three exposure groups) for extremely versatile multiple flash operation. High-speed synchronization mode allows synchronization at any shutter speed. Rear-curtain and stroboscopic modes are also available.

The Metz 40MZ-2 is a powerful flash that offers cordless TTL control, nine memory settings and stroboscopic capability. It has zoom ability to cover 24mm to 85mm, with a built-in diffuser to soften and spread the light.

The Minolta 5400HS offers sync speeds up to 1/8000 sec. with the Maxxum 700si. It can be used off-camera in wireless mode, as well as perform multiple flashes with the 3500xi flash. It features a dual-mode modeling light for previewing the illumination, too. Minolta also makes a macro light, the 1200AF-N, which has four individually selectable flash tubes set at right angles to each other. They can be rotated around the lens and fired separately or in combination to fine-tune shadows.

The Pentax AF500FTZ offers full TTL exposure control with the PZ-10 and PZ-1 cameras. It has stroboscopic capability and rear-curtain sync. It also provides a 1:2 lighting ratio when used with the PZ's built-in flash in Contrast Control Sync Mode. A built-in slave on the AF500FTZ allows it to be triggered off-camera as well.

The Sigma EF-430 Super is a powerful flash that offers automatic TTL exposure, stroboscopic capability and rear-curtain sync. It can synchronize the flash at high speeds with cameras using focal plane shutters. With Sigma SA cameras (as well as some Minolta and Nikons), it provides wireless TTL flash.

The Sunpak 120JTTL is the first parabolic reflector flash with TTL dedicated flash. It's powered by an accessory NiCd power pack, which enables it to deliver 200 full-power flashes at a recycle rate of 1.5 seconds and has a GN of 150. The DX12R and DX8R are dedicated ring-light flashes that can be used on camera systems with a filter ring size smaller than 77mm. The 4000AF is dedicated to Canon, Minolta and Nikon systems.