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No Strings Attached With
Wireless TTL Flash
By Jack Neubart • November, 2001
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These first three images illustrate how this tropical
bloom is affected by off-camera lighting, with and without
fill.
Photos © 2001, Jack Neubart, All Rights Reserved
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Multiple-flash lighting is
easier than ever with today’s dedicated flash technology.
When in Madeira, while working
on my Kodak Electronic Flash book (Silver Pixel Press), I found myself
photographing a spider and its elaborately fashioned web. The problem
was that my subject was several feet away, amid the shrubbery. I had
one hand gripping the SLR, the other grasping the dedicated flash, being
hampered by the length of the TTL cable connecting the two. Another
situation found me uncomfortably ensnared in a mess of cables when using
multiple shoe-mount strobes outdoors. Other problems with cable connections
are that they can come loose or become frayed, and cables that extend
any reasonable distance add bulk and weight to a camera bag.
Wired multiple flash also
involves various adapters and time-consuming setup. Moreover, this combination
may limit TTL auto operation to some degree (depending on the system).
And we haven’t even mentioned dealing with dangling cables that get
in other people’s or your own way. Enter a practical solution: wireless
TTL flash.
Wireless flash is not new.
It’s been around for a long time, employing any of various devices to
trigger remote electronic flash units. However, these devices are designed
around the use of non-TTL strobes, often relying on manual operation
and handheld flash meters to determine and control output. That’s well
and good for studio flash equipment or whenever you take a more measured
approach with portable flash units. Dedicated TTL shoe-mount strobes
for today’s electronic SLR cameras, on the other hand, now benefit from
something simpler, sans wires, to make the process of shooting with
multiple off-camera flash flow almost effortlessly.
Wireless TTL Auto Flash
For wireless TTL flash to work, both camera and flash must be designed
to support this function, one operating as an extension of the other.
Wireless TTL flash usually begins with the camera manufacturer and the
dedicated strobes designed for use within a family of high-tech SLR
cameras, and may apply solely (or to the fullest degree) to the latest
generation within that family. Moreover, for the utmost convenience
to the user, the emphasis is on wireless TTL auto flash. The availability
of wireless TTL auto flash is not limited to the manufacturer’s own
products, encompassing a few after-market strobes and even a TTL remote
module. Moreover, the camera gear compatible with wireless TTL flash
is not limited to autofocus 35mm models. Wireless TTL compatible, dedicated
strobes aimed at select models of autofocusing 35mm SLRs may also be
suitable for APS, digital, and non-AF 35mm SLRs from the same manufacturer.
And some after-market products may also be suitable for TTL-flash-enabled
medium format cameras.
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This employs the off-camera flash solely, for sidelighting
from a high angle (flash handheld). The picture is much
more vibrant. (Note: the on-camera flash was set so as not
to emit any light, but to trigger the remote unit.)
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The Wireless Connection
Wireless TTL flash is not a totally detached association: There must be
something attached to the camera to activate the remote, off-camera flash.
Depending on the system, that can be the built-in flash or it could be
an external flash or signaling device seated in (or connected by way of)
the dedicated hot shoe. Yes, even though we’re going wireless, the main
controlling unit can be attached to the camera’s hot shoe by a dedicated
adapter and cable, but that would seem to defeat the purpose of a totally
wireless system. This cabled rigging, however, might still be needed to
get around obstacles that stand in the way of sending signals to the remote
flash units. For our purposes, we’ll assume an unobstructed signal path
that leaves us totally cable-free.
Select wireless-enabled TTL
flash units can act as both "transmitter," which sends out an activation
signal, and "receiver," which, upon sensing that signal, fires the flash.
For this to happen, we obviously need at least two such units employed
together, with one serving to transmit the signal, as the "master" unit,
the other receiving the signal, as the remote, off-camera "slave" unit.
The remote strobe may be said to be "slave-synched" to the first, or simply
"slaved." Within the same family of strobes we may find wireless-TTL flash
units designed without the ability to act as the master unit, simply serving
as the slave flash. This option reduces the cost, and makes sense, since
we don’t need more than one master strobe, except perhaps as backup.
The Signal
What constitutes a signal? When it comes from the dedicated flash, it
is generally a very short burst of light at a pre-defined frequency filtered
in the near infrared. To further ensure that it does not contribute to
the exposure, this burst of light is emitted prior to the actual exposure,
similar to a pre-flash that some TTL systems use to measure the required
flash output. The pulsed signal is coded. This coded signal carries all
the information both camera and strobe(s) need to communicate back and
forth, maintaining full functionality, as if the flash were on-camera
and to the degree allowable by the system.
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Finally, both units were used, with the diffused on-camera
flash bringing out some of the background detail. I won’t
say which of the last two I prefer. You choose.
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Master & Fill
Ordinarily, the master unit is on-camera (unless on a cable and off-camera).
When the master unit is a flash, it may serve as a fill light, with the
remote (off-camera) flash generally providing the main source of illumination.
It may be possible to set the on-camera flash so that no light is emitted,
for instance, to prevent glaring reflections in shiny surfaces directly
facing the camera, or for more dramatic lighting. Of course, a bounce/swivel
head on-camera may alleviate this concern, but then there’s the fear that
the remote flash will not read a signal that is not beamed directly at
it or that some of the indirect light may still reach the subject.
The master unit transmitting
the signal does not even have to be another strobe. Sitting in the hot
shoe, it can simply be a device that sends out the signal that triggers
the slaved strobes, without adding any visible light. In that case it
is simply called a "transmitter" or "controller." (Note: the term "controller"
may also apply to a device attached to a slaved flash.)
Each system operates according
to its own parameters. The system may offer fully automatic TTL flash
exposure control, or certain combinations of camera and flash may limit
you to manual wireless operation only, or limit you in other respects.
There may be other limitations to overall functionality, all varying with
the camera and flash. For instance, wireless TTL flash may support such
functions as flash exposure compensation, flash bracketing, high-speed
sync, and stroboscopic sequential bursts, provided these functions are
there to begin with. One of my favorites is the ability to trigger all
the strobes simultaneously to emit a modeling light, helping me picture
the combined effect of all the lights on a set. You’ll have to check the
instruction manual for your photo gear to learn the full extent of your
system’s capabilities.
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I
keep things around, knowing they’ll be useful one day,
as is the case with my cat’s white plastic medical collar.
I used this as a light tent, positioning the miniature
kaleidoscope in the center, on a backdrop of Mylar and
gold-tone reflective material. To bring out the gem-like
stones at the front, I positioned one flash on the right,
a second on the left, parallel to the first, with matching
output. Each flash was positioned within inches of the
tent and aimed so that the light from each strobe hit
the tent at a glancing angle, not full force (we’re
lighting through thin plastic). Hand holding the camera,
I poked the lens through the opening. Owing to the highly
reflective nature of the kaleidoscope barrel, a distorted
reflection is captured, but serves to break up the monotony
of the uniform silver finish.
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Maintaining The Proper Balance
Now that we’re equipped with a camera and two or more flash units supporting
wireless TTL auto lighting, we realize one requirement: If we pop all
the strobes as is, the lighting may be even, assuming the same model flash,
and will almost surely produce multiple shadows. We could overcome this
problem by placing the strobes at varying distances, add a diffuser, bounce
the light, or set the zooming head manually to respectively different
positions--all of which would affect the quality of light.
Another alternative is this:
Provided this function is built-in and supported by all the "connected"
gear, simply use the on-camera master unit to define a ratio of relative
brightness levels that places greater emphasis on one or more lights compared
with the other supporting lights. For example, the off-camera key light
that provides the defining illumination should produce the defining shadows.
So we set the ratio to ensure this result.
Unfortunately, this may not
be enough to guarantee that the secondary lights won’t be so strong that
they cast even a faint shadow. Using the modeling light function helps
you visualize the results with your setup, but even then, there are no
guarantees--nothing beats a true (incandescent/tungsten) modeling light.
Given that, I’ve found it was still necessary to physically reduce the
light output further (using a combination of the methods just outlined),
to totally obliterate the uninvited shadows. It may also help to work
with flash units of unequal output (higher and lower guide numbers) to
begin with.
Where applicable, the degree
of ratio control varies with the camera/ flash system, from simply 2:1
to 8:1, controllable within the master unit. This option may extend to
a ring flash, albeit on-camera, with a ratio adjustment available between
the two flash tubes. The ring flash may further function as the master
unit, triggering an off-camera strobe, which may be used to shed some
light on the background, for instance, when you want to add an environmental
feel to your close-ups.
The system may also be designed
to automatically reduce flash output of the on-camera flash when it encounters
backlighting (from available light), to produce a more natural rendering
with fill flash. That may even extend to the use of an external TTL flash
in the hot shoe, with another dedicated flash positioned off-camera and
backlighting the subject.
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This
shoe-mount flash has a switch at the bottom, whereby
it can be set to serve as the master/transmitter or
slave/receiver unit, or neither. The LCD panel shows
the flash is set to a specific channel, the same channel
used by the remote transmitter and any other flashes
that should fire at the same time. There is also group
designation (A or B). The first flash can be designated
"A" and the second "B," whereupon the respective amounts
each light would contribute to the picture could be
set on the ratio scale (which is on the transmitter).
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Quiet--I’m Channeling
Routinely a dedicated wireless TTL system gives you a choice of two or
more channels. Just as selecting a channel on your TV lets you see only
the programming on that channel, selecting a channel on a dedicated flash
system tunes each component--the transmitter/master and the receiver/slave--into
a signal of a specific frequency. The transmitter sends the triggering
signal to any flash attached to or integrated into a receiver locked into
the same channel. You can have one or more flashes assigned to one channel,
but multiple channels cannot be assigned to the same flash unit.
Why do you need separate channels?
You may find that someone else is working with a similar system that is
triggering your own--meaning they’re set to transmit on the same frequency
as your lights. If this happens, you may have to select a different channel
for all your flash equipment. Or you yourself may have multiple cameras
and strobes set up, and to avoid popping all the lights at the same time,
set one (or a group) of flash units on one channel, a second light (or
group of lights) on a different channel, and so on, for the remaining
available channels and lights. On the face of it, it may be no big deal
to pop the strobes at the wrong time, until you realize that the flash
you need at the moment is still recycling, or that the batteries have
worn down from unnecessary use. Or you may be using a long exposure on
a moving subject, and you want a different strobe popping at different
intervals to catch different stages of movement.
Also, depending on the system
employed, it may be possible to not only set channels, but to assign different
strobes to different groups, all firing under the same channel at the
same time. For instance, Group A (which could consist of only one light)
might be the on-camera strobe serving as fill, with reduced output set
on the ratio scale; Group B (again possibly only one light) serves as
the off-camera main light. It might also be feasible to position another
light or group of lights (Group C) to illuminate the background. You can
get more creative and, with the appropriate accessories, set the main
light up as an umbrella light to produce a flattering portrait against
a painted (Group C illuminated) backdrop. In this case, the fill light
will have to be toned down considerably to avoid casting objectionable
shadows, since the umbrella light is significantly weakened, as is true
of all bounce lighting.
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Signal Blockers?
Any way you approach it, for it to work correctly, wireless TTL mandates
that the remote flash (or more to the point, the receiving sensor) be
positioned within a certain distance and at the right angle so that
it reads the transmission signal. That’s less of a concern indoors or
in enclosed environments with reflective surfaces nearby. To test out
my system, I even aimed the transmitter at a closed window, from a few
feet away, with the slaved flash on a chair, its sensor partially blocked.
I still managed to trigger the flash.
Armed with that information,
I ventured out to the zoo, only to learn that additional restrictions
on flash placement made triggering the off-camera flash (by the on-camera
strobe) a tricky proposition. Holding the flash aloft and out of sight
in my left hand, I found that a twist of my hand or arm could make the
difference between success and failure, since my entire attention was
focused not on the flash but on a subject that was often moving. Other
situations found me placing the flash on a tabletop tripod on a level
shelf outside a glassed-in exhibit. Moving a little too far from the
off-camera flash resulted in a loss of triggering signal, apparently
resulting from an increased angle. Moving the flash closer to my position
made a world of difference. Moreover, indoors, such things as fluorescent
lights and cell phones could interfere with the signal, according to
one manufacturer. Outdoors, bright light hitting the sensor could be
the culprit.
In more open environments,
both at the zoo and in a large botanical conservatory, placement of
the off-camera light proved even more critical. I had to keep reminding
myself to swivel the flash head to ensure the sensor was aimed correctly
to read the on-camera flash. With flash recycling often coming so fast,
it wasn’t possible to check to see that the remote flash fired before
it had already recycled. There were times when I simply turned to someone
standing nearby and asked if that person wouldn’t mind observing and
telling me if the off-camera flash had fired. I was relieved to learn
that it had.
Alternatives To Wireless
TTL Flash
You may own an older strobe or camera, but still want to shoot with
multiple-flash setups, sans TTL control. You’re in luck: the necessary
accessory is practically at hand, ranging from very basic and economical
to fairly high tech and expensive. Just remember that this route involves
a more studied approach to exposure control, even with auto-sensor flash
units, and possibly involving a flash meter when the strobes are used
in manual mode. You may also need a standard PC sync socket on the device
to be triggered.
The simplest is a photo-optical
slave, which attaches to the off-camera flash. These devices come in
various sizes--some extremely small. A photo slave is sensitive to visible
light, responding to the short bursts emanating from a flash, so that
a separate transmitter is not needed. It ordinarily attaches to the
X-sync contact on the off-camera flash, in place of the PC sync cord,
for non-dedicated operation. Size, cost, and sensitivity generally go
hand in hand. Optical slaves are reliable so long as they are in line
of sight from the triggering burst of light. Indoors, light bouncing
off nearby walls may be enough to trigger the remote flash. Some flash
units come with a built-in optical slave sensor, so they can be triggered
remotely without additional accessories. The basic drawback to an optical
slave is that any strobe, or possibly other blips of light, can trigger
it. In contrast, coded infrared slave systems are not triggered willy-nilly
by any flash unit or light sources. They may provide such options as
channel selection, and are not hampered by obstacles as easily as optical
slave sensors.
A radio slave is another
alternative, very often used in place of a cable release, to remotely
trigger the camera itself along with off-camera flash units, or simply
to trigger one or more remote strobes alone. This triggering system
comes in handy when the slave unit may be hidden behind obstacles that
would otherwise interfere with other wireless options, or where other
bursts of light may inadvertently trigger the system. These systems
are often the first choice among professionals, for use indoors and
out. Strong electrical or electromagnetic fields, however, may disrupt
transmission/reception, thereby interfering with overall functionality
(which is why pros sometimes need to hardwire their lights). Of these
radio remotes, we even found a model with a digital LCD readout and
high tech features to match. As with infrared devices, both a transmitter
and receiver are required for radio remote operation.
Why Won’t My Wireless
TTL Slave Flashes Fire?
Each system operates according to its own parameters. The following
are generic causes/solutions that may or may not apply in your specific
situation.
- The obvious: are the master/transmitter
and slave/receiver units switched on; are the batteries inserted and
fresh; are any of the units in standby mode?
- Does the camera or flash
support wireless TTL flash? Only manufacturer-specified combinations
work in this mode.
- Where necessary did you
set the receiving units as slaves and the master unit as master; did
you attach the slave controller to the slaved flash?
- If the built-in flash
is used to trigger the slave units, is it popped up, in its ready
position?
- If a hot shoe connection
is used, is the master unit seated correctly/fully in the hot shoe?
- If a remote cable is
used with the master unit are the connections firmly in place at both
ends; is the cable damaged?
- The units may be recharging--a
pre-flash may have inadvertently triggered the slave units, or you
simply didn’t wait long enough. The master unit also needs time to
recharge. Monitor ready lamps on all involved components. If the system
signals it’s ready by blips from the AF assist beam on the flash,
monitor that.
- There may be some interference.
The system is most reliable indoors, where nearby walls can reflect
and redirect the signal to the receiver, unless something is blocking
it or the outgoing/transmitter signal, or otherwise interfering with
the signal. Some systems are subject to interference from such things
as nearby fluorescent lights and cell phones. It may also be time
to attach a TTL remote cable to the transmitter to try to get around
nearby interference, or simply to switch to a TTL cable system all
around. Radio remotes and optical slaves may not be usable, unless
your camera and strobes have the necessary PC sync socket for conventional
flash firing, keeping in mind this bypasses all TTL operations, requiring
full manual exposure control and possibly a flash meter.
- Outdoors, bright light
hitting the sensor may interfere with remote triggering on the slave
units.
- Distance--the slave units
may be too far from the master/transmitter unit.
- Angle--the slave sensor
is facing the wrong way or the angle exceeds acceptable parameters.
If the flash has a swivel head, direct the head at the subject; aim
the body (with sensor) at the transmitter on-camera.
- The wrong channel has
been set on the transmitter/master unit or on the receiver/slave unit.
Slaved strobes can only respond to a signal on the same channel as
set on the mater unit transmitting that signal.
WIRELESS TTL FLASH COMPATIBILITY
The following table lists the cameras, flash units, and accessories
that can be used for wireless TTL flash operation. Select camera-flash
combinations may permit operation that takes full advantage of the latest
advanced technologies incorporated in the camera and flash units, beginning
with full TTL auto flash control, whereas others may limit functionality
in various ways (see Comments). With certain systems, the built-in flash
acts as the master unit, whereas with others, a special transmitter
or hot-shoe flash is required (exclusively or as an alternative to the
built-in flash) to activate off-camera slaved strobes, which themselves
may require a wireless controller.
Manufacturers/Distributors
Brandess-Kalt-Aetna Group, Inc.
(847) 821-0450
fax: (847) 821-5410
www.bkaphoto.com
Calumet Photographic Products
(630) 860-7447
fax: (800) 577-3686
www.calumetphoto.com
Mamiya America Corp.
(914) 347-3300
fax: (914) 347-3309
www.mamiya.com
Omega/Satter
(410) 374-3250
fax: (410) 374-3184
www.omegasatter.com
Phoenix Corporation of America
(516) 764-5890
fax: (516) 764-5970
www.phoenixcorp.com
Quantum Instruments, Inc.
(516) 222-6000
fax: (516) 222-0569
www.qtm.com
R.T.S. Inc.
(631) 242-6801
fax: (631) 242-6808
www.rtsphoto.com
The Tiffen Company
(716) 328-7800
fax: (716) 328-4186
www.tiffen.com
ToCAD America Inc.
(973) 428-9800
fax: (973) 887-2438
www.tocad.com
Vivitar Corporation
(805) 498-7008
fax: (805) 498-5086
www.vivitar.com
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