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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
color.
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.
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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 dis-tance. 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
Understanding
TTL
Through-the-lens metering (TTL) provides the means by which
cameras achieve accurate flash exposures. Basically, the light
emitted by the flash reflects off of the subject and back to
the camera. The light passes through the lens and hits the built-in
sensor. When the camera determines that sufficient light has
hit the subject, it quenches the flash.
Today’s cameras offer significant advances over this basic
concept. Cameras now can include multiple-pattern flash metering,
the incorporation of distance information and pre-flashes for
handling extremes in tonality and AF sensor data for biasing
exposure for off-center subjects.
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.
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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 color.
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 color 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 color cast, as that color 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
(List Price: $26) 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
(List Price: $21 to $140) 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 (List Price: $512) 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.
Auxiliary Flash Comparison Chart
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