The Nikon Creative Lighting System
Wireless, Remote, Through-the-Lens Metered (iTTL) Flash!
Review posted: 07/31/2006
Nikon has been a leader in flash technology for photographers for quite some time. Their 3D matrix metered flash systems integrate distance information from the lens with exposure information from the camera to make fill-flash metering uniquely easy to control. In a very practical sense, the accuracy of 3D matrix flash metering means that the photographer can spend less time worrying about how to work around the vagaries of the flash system, and more time concentrating on his/her creative vision.
With iTTL (the "i" is for "intelligent" TTL), Nikon further extended the capabilities of their flash technology. The iTTL system makes use of the 1005-element RGB sensor used for the camera's main exposure system, improving the accuracy of the metering pre-flash. At the same time, wireless capability was dramatically expanded, with the implementation of true multi-unit, TTL wireless flash autoexposure. In our view, this is the most amazing part of Nikon's Creative Lighting System: Not just that it provides automatic flash operation without wires, but that it offers true Through The Lens (TTL) metering for flash exposures, even with multiple remote flash units: With an SB-800 speedlight as a master controller, up to three separate groups of SB-600, SB-800, or SB-R200 strobes can be controlled independently, each group consisting of an unlimited number of units. Various Nikon cameras with built-in strobes (the D70, D70S, and D200, as of this writing) can also serve as the master controller, with varying degrees of control.
When we first heard about it, the whole wireless TTL system sounded a bit like magic, but it's actually pretty straightforward once you know what it's doing. (Straightforward, but no doubt requiring a lot of clever engineering.) The key to it all is strobe circuitry that can turn on and off very quickly, and fire multiple precisely timed bursts in a very short period of time. The iTTL system uses this capability in two ways. First, it uses rapid series of very brief pulses of the strobes to let the Master Controller "talk" with the various groups of remote units. The Master can command groups of remotes to fire either very brief pulses for metering, or more powerful flashes for the exposure itself. It does this by treating the flash head as a digital data channel, encoding commands about the type and intensity of pulse to fire in the form of rapid bursts of light.
The second way that the fast-pulse capability facilitates iTTL is by making it possible to determine exposure levels from multiple flash groups very quickly. (The speed is important, as you don't want the flash exposure determination to introduce an unacceptable shutter lag when working with multiple groups of speedlights.)
The way the iTTL system works is that the camera tells the Master controller to individually command each group of remote flashes to fire a metering pulse. Using its internal TTL sensors, the camera measures the amount of light coming from each strobe group, and integrates the light readings from all of the strobes with the ambient light coming through the lens. Via the Master controller, it then tells each strobe group how much light to emit for the exposure itself, and triggers them to fire when the shutter is opened.
If this sounds like a lot that has to go on before the shutter opens, that's because it is. It all happens very quickly though, without introducing an appreciable delay in the shutter release. (If you have several groups of strobes involved in a single exposure, and have quick enough visual reflexes, you can actually see a very brief period of flickering strobe flashes before the main exposure itself.)
The results are really pretty amazing. You can more or less scatter strobe units around the set any which way you want, and the iTTL system will deliver not only an accurate default exposure, but perfect control over the light being delivered by each group.
In this article, we'll explore Nikon's Creative Lighting System a little bit, using the operation of a D70 camera body and an SB-800 strobe unit as the basis for the discussion. The D70 (and subsequent D70s) is a little limited in that its internal flash can only serve as the controller (that is, can't also contribute to the exposure itself), and can only control a single group of remotes. By contrast, the more recent Nikon D200's flash can contribute to the exposure itself, and can also control two groups of remotes. The D70 works just find for the purposes of this article though.
Caught in the Act: Advanced Wireless Lighting in Action
This really has nothing to do with the D70 and SB-800's photographic capabilities, but it's a cool picture, so I thought I'd share it: We were debating how many flash pulses we thought we were seeing coming from the D70 and SB-800 in wireless TTL mode while we were measuring the shutter lag in that mode. To settle the debate, one of us held the SB-800's head directly above the D70's built-in strobe. The other took another camera, pointed it at the combination, and panned it rapidly with a long exposure, just as Luke pressed the shutter. It took a few tries to catch it just right, but the shot above shows that there are actually a total of five flash pulses emitted by the D70 and SB-800 in the process of making one wireless TTL exposure. (All this happens in about 0.6 seconds.)
Here's what we think is happening in the shot above:
- D70 fires a "wake up" series of command pulses, to get
the attention of any remotes that might be out there, lying dormant. (Note
that what looks like a single bright flash here is actually a very rapid series
of communication pulses, carrying digital data from the D70 to the remotes.)
- D70 fires a command pulse stream to instruct the remote(s) to get
ready to fire a metering pulse.
- D70 fires a single, (low power) trigger pulse. The SB-800 fires
in synchrony with it. This is the metering pulse.
(Then there's a pause, while the D-70 digests the results of the metering pulse, and computes the correct exposure based on its TTL measurement.)
- The D70 fires a series of command pulses, instructing the remotes
to get ready for the main exposure flash, and telling them what power level
to fire at.
- The D70 fires a single trigger pulse. The SB-800 fires in synchrony
with it. This is the main exposure flash.
Some Remote Flash Examples
OK, so all this technology sounds wonderful, but how well does it work? Without exaggerating, really, really well. The examples here are borrowed from our original D70 review, and the press of too-much-to-do kept us from spending more time with it, but we shot the images below to give some idea of just how big a difference off-camera flash can make, versus the limitations imposed by the on-camera strobe head. Being able to move the light source around freely really opens up what you can do with flash photography.
In these photos, we didn't try to duplicate the same shot with on/off-camera lighting, as direct comparison without variations wasn't the point. - Although the photos of Mickey Mouse the Cat (his name, no wonder he's neurotic) ended up being very similarly posed and framed simply because he was willing to sit more or less still while assistant Chris and I fiddled around with the camera, flash, and soft box. (We used a Photoflex medium Movie Dome for this shot, holding the soft box and SB-800 by hand.)
Onboard flash: Contributes or not?
Experimenting with these various remote modes, we initially were puzzled by the fact that the onboard flash did indeed seem to affect exposures somewhat, contrary to what the D70's manual and Nikon themselves said. After a fair bit of experimentation though, we figured out what was going on. It turned out that the shots in which we saw an exposure influence from the onboard flash were all taken at very close range. After the remote units have been configured via the series of rapid communications pulses described earlier, they wait for a single (weak) strobe pulse to trigger on. The D70's trigger pulse is quite dim, but at close range (a few feet or so), it's still bright enough to have at least a small effect on the exposure. The workaround (assuming that you indeed don't want the onboard flash to make any contribution to the photo) is simply to cup your hand in front of the camera's flash head. In my experience, there was always more than enough light left spilling around my hand for the D70 to communicate with the remote SB-800, while its effect on the subject itself was all but eliminated.
SB-800 Basics (and one important note)
Let's take a bit closer look at the SB-800 speedlight. (The SB-600s features are essentially the same, the primary difference being that the SB-600 can't act as a controller itself. It works as a highly-capable on-camera strobe, or a remote unit with the full capabilities of the Nikon Creative Lighting System, but can't control other flash units as a master. The SB-R200 units are very small, and can only work as remotes, as they have no provision for a hardwired sync connection.)
In truth, the SB-800 is really deserving of a more extensive review than we have time for just now, but the following should give you some idea of its capabilities and how to use it.
The shot above shows the SB-800 perched on the stand that ships in the box with it. This is a very handy accessory for a flash that's likely to be used more often apart from the camera than mounted on it.
There's not a whole lot to see on the front of the SB-800. The flash head rotates 270 degrees horizontally, and 90 degrees vertically, letting you bounce the flash pretty much wherever you might need to when it's mounted on the camera. at the bottom of the front panel is a red-tinted window that hides the bright AF illuminator. This is a very bright red LED that's behind a diffraction grating. When enabled, it projects a crosshatched pattern whenever the camera's AF illuminator would normally trigger. Useful AF range will vary with the lens and aperture in use, but Nikon rates the range at 33 feet (10 meters) with a 50mm f/1.8 lens. Not shown in these photos is the included optional Quick Recycling Battery Pack, which attaches to the right side of the SB-800. (As viewed from the rear, on the left side in the photo above.) This is simply a small plastic compartment that attaches to the side of the SB-800, in place of its battery compartment cover. It carries an additional AA cell, boosting the total battery voltage, and reducing cycle times by about 25%. (Full-power recycle time with freshly-charged NiMH AA cells is nominally about 4.0 seconds. Adding a fifth cell in the Quick Recycling Pack drops that to about 2.9 seconds. Recycle time for less than full-power shots is proportionately faster.)
Also visible on the front of the unit is a small plastic cover that protects the external power terminals. These accommodate any of three different external power packs that Nikon sells, which provide both faster recycling (down to 2.0 seconds for full-power shots) as well as greater battery life.
Just visible on the right side of the flash (left in the photo above) is the small rubber flap that protects the external sync contacts. There are two sets of contacts here, a standard PC terminal, and a proprietary 3-terminal connector for use with Nikon's flash extension cords.
The rear of the SB-800 reveals its LCD panel and controls. At lower right is the on/off switch, with the Ready indicator light just below it. The lever that locks the strobe to the camera's hot shoe is at the bottom, and a red button labeled Flash at lower right is for test-firing the strobe. The gray button above the LCD triggers the flash in a modeling light mode, a very rapid series of strobe pulses that blend visually to produce a near-continuous illumination of the subject, so you can check lighting and shadows.
Below the LCD, a Mode button selects from among the SB-800's various operating modes. Options include TTL, Manual, Auto Aperture, Guide Number (essentially a finer-grained manual adjustment), and RPT, or repeating, in which you can program the unit to deliver a specific number of stroboscopic pulses, at rates ranging from 1 to 100 flashes per second. (The number of flashes will vary as a function of flash rate and power level. Power can be adjusted from 1/8 to 1/128 of maximum, and the number of flashes can be varied from one to as many as 90.)
At the bottom center of the rear panel, a 5-way rocker switch is used for navigating LCD menu items and manually adjusting the SB-800's zoom head. The angular coverage of the SB-800 can be adjusted to match the field of view of a 24-105 mm lens on a full-frame 35mm camera. A wide-angle diffraction lens can be pulled out from above the flash lens and flipped down over it to accommodate lenses as wide as 14mm. Pressing the center of the rocker control actuates the Set button, which confirms menu choices. Pressing and holding the Set button for more than 2 seconds calls up a hidden menu that lets you switch the flash between normal, master, and remote operation, as well as set a variety of other less-frequently accessed flash parameters such as default ISO, LCD contrast and backlight, etc.
SB-800 Menu Screens
As noted above, there's not nearly enough space or time here to go into all the SB-800's features, but the menu screens shown below will give some idea of its capabilities.
|SB-800 non-wireless mode menu screens|
|TTL Balanced Fill-Flash (TTL BL) mode will probably be what most people use most of the time. In this mode, the camera and flash work together to try to deliver an even balance between subject and background lighting. It displays the ISO currently selected on the camera and its resulting estimate of its working range at that ISO. Also shown are an icon indicating that the attached camera supports the Creative Lighting System, and current focal length and aperture setting.||Normal TTL mode is very similar to TTL BL mode, but here the emphasis is solely on the subject. Useful when you want to highlight the subject, and don't care (or may prefer) that the background is over- or underexposed.|
|Auto mode is the way most conventional autoexposure flash units work. In this mode, you set an aperture value on the flash itself, and the flash adjusts its exposure (as measured by its own internal sensor) to produce a good exposure with that aperture value and whatever ISO the camera is currently using. You can then manually adjust the actual exposure by varying the lens aperture.||Auto Aperture mode represents a refinement on normal auto operation. In this mode, the camera tells the flash what ISO, focal length, and aperture it's using, as well as any desired flash exposure compensation, and the flash calculates the needed exposure itself, and meters it with its own built-in (that is, non-TTL) sensor. Operation in this mode is similar to that in A mode, but the flash compensates for any changes in aperture, and you instead control the exposure by adjusting the flash exposure compensation setting.|
|In Manual mode, neither the camera nor the flash exerts any control over the exposure. You simply tell the flash what power level to use. Options range from 1/1 (full power) to 1/128.||"Distance Priority Guide Number" mode is something of a mixture of Manual mode and auto-exposure. It lets you set a fixed distance at which you want to achieve proper exposure, after which the flash will automatically adjust for variations in ISO and aperture. (The range of possible distances will of course vary directly with ISO and aperture.)|
|This is the SB-800's stroboscope mode. You can program it to emit rapid pulses of light at rates ranging from 1 to 100 flashes/second, with power levels ranging from 1/8 down to 1/128, and in series ranging from 1 to 90 pulses in length. (Note though, that the maximum series length will be a strong function of the power level selected, and a weaker function of the pulse rate.)|
|SB-800 wireless mode menu screens|
When acting as a master controller in Nikon's Creative Lighting System, the SB-800 can independently control exposure modes and power levels for itself and three groups of remote flash units. It can also be assigned to one of four possible control channels, so as many as four different photographers can use Nikon remote flash units at the same venue without interfering with each other.
Note that in this mode, you can not only set the exposure levels of each group of remote flashes, but their operating mode as well. Options include TTL, non-TTL Auto, and Manual modes. (In the shot above, the master and Group B are running in TTL mode, with different exposure offsets, while Group A is set to Auto mode with +0.3 EV of exposure boost, and Group C is set to manual mode, at 1/64 power level.
|This is the wireless mode that
most D70 owners will likely use. (Unless they have multiple SB-800 units
and run one as a master, attached to the camera.) Here, the only options
are which channel and group you assign the flash to, and what focal length
you set its zoom head to.
(NOTE that you need to assign remote strobes to channel 3, group A in order to work with the D70 or D70s. The D200 can work with any channel, and can control groups A & B.)
|For compatibility with older Nikon wireless flash systems, the SB-800 also supports the "SU-4" signalling system. In this mode, you can select either auto exposure, or a manual mode that lets you set the exposure of different flash units separately. (In the screen shot shown above, I've selected a power level of 1/3 stop below 1/2 power.) In this mode, there's no autoexposure option for adjusting the power of different units.||I wouldn't personally find a great need for it, but you can slave together multiple SB-800 or SB-600 units, firing in stroboscope mode. The same range of control over power levels, flash rate and burst length are available remotely as when the strobes are connected directly to a camera. (I can imagine this being very useful for many scientific or industrial applications, using the SB-800s for time/motion studies.)|
Click on the image to view the video.That about wraps up this brief exploration of the Nikon SB-800 speedlight, and its remarkable remote-control TTL flash exposure capability. For a little flavor of how you can use a set of SB-800s and SB-600s in practice though, check out the video below, in which Dave describes how we used Nikon's Creative Lighting System for high-quality on-location product photography at the Spring 2005 PMA show in Orlando, Florida. The setup of two SB-600s and two SB-800s that we used for the PMA shots was really just remarkably effective. It made it easy for us to produce studio-quality product shots with a very portable, compact setup.
As of this writing (July, 2006), Nikon makes three different flash units that can all operate as part of their Creative Lighting System:
The SB-800 is the flagship of the line, with a zoomable tilt/swivel head and an ISO 100 guide number ranging from 38 meters/125 feet at 35mm to 56 meters/184 feet at 105mm focal lengths. The SB-800 can serve as an on-camera strobe, a master controller, or a remote unit, and currently sells for $300-400 at retail.
The SB-600 also has a zooming tilt/swivel head, but is slightly less powerful than the SB-800, with an ISO 100 guide number of 30 meters/98 feet at 35mm. The SB-600 can operate as an on-camera flash unit or as a slaved remote, but can't function as a master controller in the system. In exchange for its reduced capabilities, it can be found at retail for a good $100 less than the SB-800s.
A more recent addition to the line is the SB-R200 wireless Speedlight, a small unit that's available either as part of the R1 or R1C1 macro flash kit, or separately by itself. These tiny strobe units only function as remotes, and have ISO 100 guide numbers of only 10 meters/33 feet, but sell for less than $150 at retail.
One parting piece of advice about Nikon's Creative Lighting System: Don't play with it until you're ready to buy a complete setup: Once you've experienced its flexibility and the creative power it gives you, you may not be able to live without it! (On the other hand, it's a system you can easily grow into: If you start with a D70 or D200, you could add an SB-600 to start, to give you basic off-camera flash capability, then add others as budget permits. With the D70 or D70s, you may want to make your second or third flash be an SB-800, so you'll have the ability to control multiple groups of remotes.)