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A ring light is a flash unit that has special characteristics
that are optimized for specific kinds of shooting. Doctors and scientists use
ring lights to provide even illumination for extreme close-ups shot with
macro lenses, and many amateurs use them to shoot stamp or coin collections
and the like. We know of a few pros who use ring lights to shoot architectural
details and high-fashion portraits.
The ring light’s defining feature
is its circular, or doughnut-shaped flash tube and reflector. The reflector
housing is generally threaded to fit regular series filters or the threads
on SLR lenses.
Ironically, the ring light violates the general
rule of lighting placement. Instead of being held away from the lens in order to produce
better modeling, the ring light's axial position is intended to produce
no noticeable shadows and, therefore, little modeling. And sometimes, that's exactly the kind of light you need.
First, let's look at the different ring lights you can choose from.
Power and size
The beam angle of most ring lights is 60° to 70°. This is wide
enough for use with a 35mm wide-angle lens on a 35mm camera, but generally
you would want to use a longer lens for close-up work. If you get too
close to the subject with any ring light, its illumination will be uneven--the
center will be darker than the outer area.
Hence, 100-105mm macro lenses,
which have longer working distances than 50-60mm macros, work better for
close-up shots with ring lights. They also give live subjects like this
honeybee more room, so you’ll be less likely to spook them.
You don’t want to bug a bee!
Power is the main thing to consider when you're shopping for a ring light.
Many small units, powered by AA cells, are best suited for close-up work.
Typically, reflectors are about 3-4 inches in diameter. With a ring light
of this size, you can photograph objects as close as two inches from the
lens.
Larger units can be used for photographing small machinery. They can even
be used for lighting individual or group portraits—if this kind
of flat illumination suits your specific needs. If your lens is too small
to fit the thread of a larger ring flash, you can use a step-up adapter.
Larger lights are available in both battery and AC-powered units. Power
ranges from 25 to 200 watt-seconds. Reflectors on larger ring lights have
a four-to five-inch diameter, and you can shoot a subject as close as one
foot from the camera lens
Studio ring lights
The largest ring lights are studio units that handle from 400 to 2400
watt-seconds of power. Generally, they are AC-powered, but can be powered on location with portable generator. The reflectors are as large
as 16 inches in diameter. They can be mounted either on the camera or
on a light stand directly in front of the camera so the lens looks through
the ring light.
Scientific and industrial uses
Professional photographers are frequently called upon to produce detailed
photographs of machinery or apparatus with complex, overlapping parts.
Medical and biological photographers are often required to deliver images
that have the greatest possible amount of unobstructed detail and information.
If you use a single flash off to the side of your camera, some of the
overlapping parts of a complex subject can cast obscuring shadows on other
parts. A second flash, on the opposite side, would lighten these shadows,
but may cause other problematic shadows.
A simple subject—one with minimal depth and no overlapping parts—could
perhaps be photographed perfectly well with the classic two-angled-flash
setup, but a complex subject, such as an assembly of gears like the examples
shown here, or an electronic wiring harness, call for a different approach.
This is where a ring light really comes in handy.
Because a ring light emits a nearly uniform cone of light that's essentially
on axis with the camera's view, no part of your subject will cast an annoying
shadow visible from the camera position. Even relatively deep enclosures,
like those common in electronics assemblies, are uniformly lit so all
the working parts are clearly distinguishable. Deep enclosures can be
difficult to light by any other means.
 Actually
there will be a halo-like shadow around the subjects as seen on this photo
of a pencil, but the shadow will be very faint due to the much greater
intensity of the direct light.
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Ring lights don't work very well on glossy surfaces. You'll get too much
glare from the flash tube's reflections. In such cases, off-camera flash
may be a better choice. Alternately, you could opt to tilt the subject
slightly so the glare is moved to the side, as shown in these photos of a
toy Volkswagen Beetle.
Small-object photography
Ring lights are ideal (and best known) for close-up photography of very small objects,
including insects and botanical specimens. These lights are particularly
useful when you're photographing on location. The ring light always aims
itself—wherever you point the camera, the light's right there, pointing
in the right direction.
The flat lighting effect is equally suitable for shooting on black-and-white
or color. The lighting ratio is virtually 1:1. The illumination appears
shadowless, and you're not likely to exceed the contrast limitations even
with digital capture or narrow-latitude color slide film.
 You
can modify ring lighting somewhat by covering portions of the flash head
with black tape to block off some of the light. This will partially eliminate
the symmetry of the lighting to give slightly more directional effect.
Indeed, some close-up flashes, like the Nikon SB-29, (which aren’t
technically ring lights but give similar results) use this concept. They
feature two flashtubes mounted on opposite sides of the lens.
You can
shut off or partially cover either flashtube to enhance contrast, as well
as rotate the flash head to direct the light from above or below the subject.
The sb29s seen here is similar to early models of the olympus ring flash.
Exposure correction
Calculating flash exposure in small-object photography is not as simple
as it is in regular flash photography. As you get closer to your subject,
the effective aperture of your lens becomes smaller. As a result, the
light reaching the film or image sensor is weaker, so you'll need to select
a wider aperture to get the correct exposure.
One answer to this problem is a ring flash with through-the-lens (TTL)
exposure control. Some 35mm SLR makers such as the Olympus Nikon, Canon
and Pentax, offer their own close-up flashes with TTL exposure control.
After-market suppliers like Sunpak, Vivitar and others offer similar units.
Because the photocell reads the light actually passing through the camera
lens, it automatically compensates for the dimmer image given at very
close subject distances. You should test and bracket
to get the best results. An automatic exposure-compensating system relieves
you of most concerns about exposure, leaving you free to concentrate on
the subject and the picture. And if you have a digital camera, you can check results in the LCD screen.
To make focusing easier in dim light, some ring lights have built-in modeling
lights. Some are small incandescent lamps built into the head. Other flashes
briefly fire the flashtube at low power, similar to the redeye-reduction
systems in point-and-shoot cameras.
Fashion photography
Relatively powerful ring lights, delivering from 40 to 200 watt-seconds
or more, are occasionally used in fashion photography for special-effect
lighting. Ring lighting works well with some kinds of clothing, such as
spandex. The frontal illumination can highlight threads in the material.
However, you'll get little modeling on your model's face. You may want
to accentuate the face makeup, to compensate for this.
Red-eye is another likely problem when photographing people with ring lights.
Red-eye is more evident if the existing-light level is low, so that the
pupils of your subject’s eyes are large. Have the subject turn his or her eyes slightly away from the camera
lens to reduce the chances of getting red-eye. Then again, a few pops of a decent-sized ring light will shrink
the subject’s pupils pretty quickly. When shooting portraits, you
can also handhold a ring light off-camera, just like any other flash.
The results are similar those you would get with any regular diffused
off-camera flash unit.
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