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Stopping action with the Paul C. Buff Einstein 640 monolight
Sunday, July 4, 2010 | by Rob Galbraith
The Paul C. Buff Einstein 640 is promised to be the first monolight to deliver both class leading colour temperature consistency and superior action stopping capability, one that also incorporates precise modeling light tracking, worldwide power compatibility and optional remote control of flash settings, all for under US$500 in the U.S.

Does the Einstein 640 deliver? We weigh in, focusing primarily on its suitability for strobed sports in conjunction with the companion CyberSync wireless triggering system. We also look at the bright 11 inch Long Throw and even brighter 22 inch Retro Laser reflectors, and an upcoming surprise from Dynalite that, along with the Einstein 640, makes 2010 one heck of a year for indoor sports photographers who depend on flash.

Lineup: Nikon D3S + AF-S 14-24mm f/2.8 at 16mm, ISO 400, 1/320, f/6.3. Lighting is four Einstein 640s at 160ws inside Retro Laser reflectors. Click to enlarge (Photo by Rob Galbraith/Little Guy Media)

Introducing the Einstein 640

For years, Paul C. Buff has been synonymous with affordable no-frills lighting that works. The goal for the Einstein 640 was to add the frills, and then some. As of this writing, you won't find a competing studio monolight with the Einstein 640's breadth of features and capabilities, from any other maker at any price.

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Light in a Box: Views of the Paul C. Buff Einstein 640 monolight and optional CSXCV transceiver. Click photos to enlarge (Photos by Rob Galbraith/Little Guy Media)

Here's what the Einstein 640 offers:
  • Separate Color and Action operating modes; one is optimized for colour temperature consistency throughout the power range and the other for stopping motion

  • 5600K (50K) colour temperature in Color mode

  • Best-in-class action stopping capability in Action mode at a 320ws and below (this based on our testing)

  • Worldwide power compatibility (95-265VAC, 50Hz or 60Hz, autoswitching)

  • 2.5-640ws range, settable in 1/10-stop increments

  • Full power recycle time specification of 1.7 seconds

  • Worldwide 250W quartz modeling light with precise tracking of flash output power

  • Removable Pyrex dome over the flash tube and modeling light

  • Compatibility with the Cyber Commander wireless remote control and CST Transmitter (optional CSXCV Transceiver module is required)

  • Built-in optical slave situated on the top of the flash

  • UV coated, user-replaceacle 12mm diameter flash tube

  • User-upgradeable firmware (via microSD slot)
From the Profoto D1 right on down to the cheapest no-name gear, no other studio monolight has been designed to deliver so much.

And deliver it does, for the most part. The emphasis in this article is on the Einstein 640's ability to freeze action, but we'll touch on certain other slick features and point out some of the unit's shortcomings too. The Einstein 640 is great, but has two hardware flaws that are being addressed by Paul C. Buff right now, so if you're considering an Einstein 640 purchase you'll want carefully consider the timing of that purchase before you plunk down your VISA card. We'll cover these flaws within the body and the conclusion.

Methods for reducing power and their effect on flash duration

To understand how the newest Paul C. Buff flash stands apart from almost all other monolights, you'll want to understand the options that flash makers have for adjusting flash power down from full and how each affects flash duration. No matter how fancy or pricey the flash, they all use one or a combo of these three methods:
  • Capacitor switching Almost all power packs, plus a small minority of monolights, will provide lower power settings by reducing the number of capacitors that are active at any one time. For example, if a pack has a three-position switch that changes the power from, say, 2000ws to 1000ws to 500ws, in almost all cases the number of active capacitors is being reduced as the power is lowered. When capacitor switching is used, flash duration shortens as flash power is reduced.

  • Voltage lowering Almost all monolights will provide settings below full power by lowering capacitor charge voltage. Reducing the charge voltage lowers output brightness but also causes flash duration to degrade. When voltage lowering is used, flash duration lengthens as flash power is reduced.

  • IGBT "tail trimming" All shoe-mount flashes, including those from Canon and Nikon, rely on an insulated gate bipolar transistor (IGBT) circuit to lower flash output below full power. At full power the IGBT isn't invoked, either not at all or not until the flash tube has dimmed almost completely after firing; either way, this means the flash burst is allowed to naturally trail off after reaching peak brightness. The result is the flash's maximum output, but also a long tail of light that can lead to blur when photographing moving subjects. An oscilloscope curve showing this, captured from a Nikon Speedlight SB-900 set to full power, is at left below.

    On the right, the SB-900 has been set to quarter power. The flash quickly reaches the same peak, but then the IGBT kicks in to swiftly quench flash output, resulting in lower total brightness. An IGBT or set of IGBTs within a flash is often referred to as the tail trimming or tail cut circuitry, because of the rapid falloff of the light that results from its truncating of the flash's otherwise slow progression back to darkness. When IGBT tail trimming is used, flash duration shortens as flash power is reduced.
Curvy: Oscilloscope traces of a Nikon Speedlight SB-900 set to full power, left, and quarter power, right

As noted above, the vast majority of monolights on the market employ voltage reduction, and voltage reduction only, when a lower power setting is selected. Which means the shortest flash duration is achieved when the flash is set to full power.

This contributes to why almost all monolights in the 300-640ws range needed for strobed sports photography in small to medium size venues lack the action stopping capability needed to produce crisp pictures of athletes in motion: none offer particularly fast flash duration at full power, and only get worse as the power is turned down.

One of the better traditional-design monolights on the market is the 600ws Elinca Elinchrom Style 600RX, and it relies on voltage reduction when set to less than 600ws. The photos below are of a wheel with 0s and 1s printed around the wheel's perimeter. It's spinning clockwise at about 300rpm and illuminated by this flash at the power settings indicated.

You'll see, as you mouse over the buttons beneath, that the numbers become fuzzier as power is reduced. That's the flash duration creeping ever longer.

Elinchrom Style 600RX
Compare that to the Einstein 640 in Action mode. To reduce flash brightness, it employs IGBT tail cut circuitry at all settings below the maximum. The use of IGBT circuitry is common in shoe-mount flashes, but not in monolights or packs.

The Einstein 640 is only the second AC-powered monolight we know of to ever incorporate IGBT, the first being the Photogenic Solair series. The Solair models, however, are specified to give fairly long flash duration in the 300-640ws power range, even with IGBTs in use. The Einstein 640 and the implementation of its Action mode make it the first monolight designed to capitalize on the action stopping benefit that IGBT circuitry can provide.

At full power, Einstein 640 flash duration is actually slightly longer than the 600RX. Step the Einstein's power down, however, and its array of eight IGBTs begin to work their magic. At about 320ws and lower, the action stopping capability of the Einstein 640 handily surpasses that of the 600RX, regardless of the latter flash's power setting.

Einstein 640 (Action mode)
That's the Action mode in action. The only downside to this mode's reliance on IGBT alone through most of the power range is an upward shift in colour temperature as power drops. For the shooting of sports indoors this is not really a problem, since the camera's WB can be set to account for the light's blue shift.

For portrait work the requirements are often different. Colour temperature consistency across different lights, perhaps operating at different power settings too, is almost always desirable. Enter the Einstein 640's Color mode. Set this way, the flash balances a mix of IGBT tail trimming (which raises colour temperature) and voltage reduction (which lowers it) to maintain a specified 5600K (50K) throughout the power range.

The oscilloscope traces show the different flash pulse you get from each operating mode. Action is on the left. Charge voltage stays constant as the power is lowered, which is why the height of the peak stays constant down to about 160ws and is higher than the peak in Color mode at all power levels (the Action mode peak would be the same height below 160ws too if the IGBT circuitry weren't kicking in before the flash tube has a chance to reach maximum brightness).

On the right is Color mode. Charge voltage is dropped below full power, which results in a peak that's noticeably shorter. To put out the same total brightness as the comparable power setting in Action mode, the duration is lengthened. The effect is more consistent colour temperature as the power drops below full, but at the expense of some action stopping oomph.

Even in Color mode, however, the Einstein 640 can still freeze motion, or at least slow it down. If your portrait subject kicks her head back and laughs at the moment you press the shutter button, you're more likely to capture a frame that's free of flash-induced motion blur with the Einstein 640 than most or all other similarly-powered monolights, as long as you can turn the power down a bit and allow the IGBTs to do their thing.

Action vs Color mode

Colour temperature consistency is important, and is one of the Einstein 640's signature features. We're going to give the topic short shrift here, in part because of the aforementioned plan to look at the light's motion freezing ability first and foremost, and also because we've had no problems thus far with the colour coming from the Einstein 640 in Color mode. It appears to be working as advertised, keeping colour close to 5600K regardless of the power setting.

The photo below is an example. Captured as a NEF with the Nikon D3X and processed through Capture NX2, no colour correction has been done, other than setting WB.

Focused: Nikon D3X + AF-S 70-200mm f/2.8G VR II, ISO 100, 1/250, f/11. Main light from right is an Einstein 640 in Color Mode set to 298.6ws and inside a Paul C. Buff PLM 86" Silver umbrella with Front Diffusion Fabric attached. Secondary light from left is an Einstein 640 in Color Mode set to 226.3ws and inside a Paul C. Buff PLM 64" Silver umbrella with Front Diffusion Fabric attached. Click to enlarge (Photo by Rob Galbraith/Little Guy Media)

Sports and the Einstein 640

The spinning wheel photos shown so far give an idea of the action stopping difference between a typical monolight and the Einstein 640. The setup below, and the resulting photos, demonstrate how the Einstein 640 performs when lighting up a real athlete.

Runway: Three Einstein 640s + three PLM 64" Silver umbrellas. Click to enlarge (Photo by Rob Galbraith/Little Guy Media)

The hurdler is leaping at close to competition speed, the camera is stationary and the framing is tight, which means subject movement across the frame is considerable. From shooting this in daylight, we know that a shutter speed below about 1/5000 (yes, 1/5000!) will lead to subject motion blur. This is a sports flash torture test, and the Einstein 640 was able to stop the action completely at 80ws. It came darned close at 160ws too.

Hold Still: Canon EOS-1D Mark IV + EF 70-200mm f/4L IS, Einstein 640 in Action mode at 80ws. Click to enlarge (Photo by Rob Galbraith/Little Guy Media)

Below you can see the progression to the ideal power level. At 640ws the blur is nasty, but by 320ws the situation has improved a lot, thanks to most of the light's blurring tail being removed from the exposure. There's another big improvement at 160ws, then the athlete is frozen solid at 80ws.

Einstein 640 (Action mode)
This is an extreme example, even within the world of sports. Volleyball, basketball, hockey: none will tax a flash's action stopping capabilities quite this much. It is, however, indicative of the sort of action stopping range the Einstein 640 offers. We've also shot basketball and volleyball practices, and what those photos reveal is that 320ws provides dramatically better stopping power than any other monolight in the 300-640ws range we've tested in the last couple of years, including 11 models from Aurora, Bowens, Elinca, Hensel, Profoto plus Paul C. Buff's AlienBees.

Of these, the 500ws Profoto D1 500, 500ws Bowens Gemini 500Pro and 300ws Elinca Elinchrom Style 300RX represent the maximum action stopping performance available in a typical monolight design in the 300-640ws territory. The spinning wheel photos for two of these flashes reveal that, while they offer faster flash duration than the Style 600RX discussed earlier, they still emit a long, blurring tail of light. Getting rid of that tail is the key to the Einstein 640's success at about 320ws and lower.

Traditional monolight design vs Einstein IGBT
Gemini 500Pro
Style 300RX
Einstein 320ws
An Einstein 640 at 320ws in Action mode won't completely freeze a moving athlete, whether they're a basketball player driving to the net or a volleyball player registering a kill. Make no mistake, though, yours indoor sports pictures will be crisper than with whatever 300-640ws range monolight you're using now.

Every 1/10 drop in power between 320ws and 160ws brings with it an action stopping improvement. 226.3ws is quite a bit better than 320ws, for example, and 160ws is that much better again. For most sports shooting scenarios, you're unlikely to need to go below 160ws to completely freeze a fast moving athlete. Though as the hurdler example shows, the Einstein 640 will give you even faster flash duration should you need it, by turning the power down to 80ws or even 40ws (flash duration improvements taper off below 40ws).

We're emphasizing the 300-640ws power range in this article because we've found that to be the sweet spot for strobed sports in venues up to a certain size. Think 1000-3000 seats but not 20,000 seats.

If the comparison is between, say, the Einstein 640 at 160ws and another monolight operating at or near that power level, the Einstein comes out even further ahead. This has been true in our testing with monolights that have a lower maximum power rating, such as the 160ws AlienBees B400, or the rare monolight that uses capacitor switching, like the 600ws Aurora Unilever Pro U600. At 150ws this flash switches to using fewer capacitors than at 600ws, with a commensurate shortening of flash duration. Even so, it doesn't come close in our testing to matching the Einstein 640's action stopping skill at a similar power level.

If you need more power than 320ws to shoot sports, or more power and even better motion stopping than one Einstein can give, you'll need to consider either multiple Einsteins per light location (which means each can be turned down to the action stopping power level you require), or a power pack + head arrangement. We'll talk more about the latter on the article's last page.

Flash duration by the numbers

The tables below list the flash duration numbers for the Einstein 640 in both Action and Color modes, plus the AlienBees B1600 and the Style 600RX. These are not manufacturer-generated figures but rather ones we measured using our own oscilloscope and photodetector equipment. The t.5 number is how long the flash pulse is above 50% brightness; the t.1 number is how long the flash pulse is above 10% brightness.

Properly interpreting flash duration numbers is hard, for reasons that could fill another entire article. This data is presented here so you can see in numeric form these characteristics:
  • At full power, the Einstein 640's flash duration is actually longer than either the 600RX or B1600
  • The full power flash pulse in Action and Color mode is identical
  • Action mode will stop motion better than Color mode, but Color mode is still decent in this regard
  • Voltage reduction is not a friend of the sports photographer


Note: The Einstein's LCD screen reports t.1 numbers for the entire power range, based on measurements done at Paul C. Buff. These numbers are higher than ours, which is mostly or entirely because we're using different photodetectors (there is no industry standard, unfortunately). This means you can't compare our numbers to Paul C. Buff's, nor does it mean our numbers are right and theirs are wrong, or vice versa. Comparing within the table above, though, is a-ok, since all numbers were generated using the same test equipment.

The Einstein 640 and equivalent shutter speed

Returning again to the spinning wheel, you can see one additional trait of the Einstein 640 that stems from its IGBT tail trimming circuitry: at about 320ws and below, the flash will freeze motion in a manner very similar to the opening and closing of your camera's mechanical shutter. This can only be said of IGBT-equipped flashes, and while IGBT isn't an absolute necessity in an action-stopping flash, it is a must if you want to accurately assign a shutter speed equivalent to a given power setting.

The photos below are a mix of both flash and ambient lighting; the former were captured with the Einstein 640 in Action mode, the latter with continuous light at the shutter speed listed. Mouse back and forth between 320ws (flash) and 1/1600 (ambient) and you'll see that the 0s and 1s are rendered very nearly the same. This holds true for 160ws and 1/4000, and for 1/6400 and 80ws. The camera's top shutter speed is 1/8000, and 40ws is actually stopping motion at a shutter speed equivalent that's slightly quicker than that. The remaining power settings are better still, though only marginally.

The previous paragraph can be summed up this way. Between 320ws and 40ws the Einstein 640 provides the action stopping power and action stopping characteristics of shutter speeds between 1/1600 and roughly 1/10,000. This is fantastic, especially in the world of monolights.

For reference, a photo of the wheel when stationary is also included, plus photos shot at 1/1000 and 640ws. The latter two show that there isn't really an equivalent shutter speed comparison to be made when the Einstein 640 is set to full power and therefore its IGBT circuitry isn't fully active. This isn't unique to the Einstein, the same holds true of any other flash's light pulse if it's not being quenched by an IGBT, as the majority of monolights and packs aren't).

Einstein 640 vs continuous light
The Einstein 640's IGBT circuitry helps it perform one other trick. It can keep pace with a camera firing as fast as 12fps. Not at full power, mind you. To fire in time with the EOS-1D Mark IV at 10fps, for example, the maximum power you can dial in is about 20ws. The 10 frames below are from an 18-frame sequence captured in succession at 10fps with Canon's current flagship sports camera. The three Einstein 640s were set to 20ws.

Einstein 640 at 10fps

Another example of the Einstein 640 keeping up to the EOS-1D Mark IV is in a nifty studio sequence, shot and assembled by Ellis Vener for Professional Photographer magazine.
Next Page: The 22 inch Retro Laser and another reflector option
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