The ARRI L7-C: cool, quiet & controllable
Dave Rimmington is a lighting cameraman who, during his BBC and freelance career, has worked on drama, studio productions, sport and music OBs, news and current affairs; he won an award from The Royal Television Society for his work in 2010. Rimmington recently tested an L7-C ARRI L-Series LED fixture on a music video shoot and what follows is his detailed review of the lamphead, reproduced by kind permission of Zerb, the journal of The Guild of Television Cameramen.
There are some items of TV equipment that have become legendary in the industry simply because they are extremely well designed for their intended role. This list includes the EMI 2001 camera, the Jimmy Jib and the Steadicam, and I'm confident that the ARRI L7-C will quickly earn a place on that list. The first time you use this lamp, it will seem instantly familiar. Styled in the traditional ARRI silver and blue branding, it looks and feels like a classic ARRI lamp. And that is the point: this is a piece of kit you can pick up and use straight away, confident of the results you will achieve.
Depending on which model you are using, the lamp weighs between 8.2 kg and 12.5 kg and is available in either manual or pole-op versions. Both can be specified with either 'active' or 'hybrid' cooling. The 'active' model is smaller and lighter than the 'hybrid' and uses a fan to cool the unit. It cannot be used without the fan. The 'hybrid' model uses both a heat-sink and a fan, and can cool passively (without the fan) or actively (with the fan). As a result it can run completely silently if necessary.
That said, these lamps generate very little heat and the fans are in any case very quiet. This lack of heat means the studio will need less air-conditioning, while in interior locations the cast and talent will not be slowly cooked by the heat from the lights with consequential effects on comfort, makeup and stress. The quiet fan and the option on the 'hybrid' model to run silently also make for happy sound people. In addition to these heat-related cost savings, the LED unit is estimated to last 200 times longer than a conventional tungsten bulb.
THE BEST OF BOTH WORLDS
Traditionally, if you wanted a daylight light source that was very efficient at turning power into light (rather than heat), you went for an HMI/MSR light source. If, however, you wanted a lamp with a high CRI (color rendering index) that could be dimmed electrically all the way to zero, you went for a tungsten source. A by-product of the ability to dim a tungsten source, though, is that the color temperature drops the more the light is dimmed. This can be very useful for warming up a scene but can also be unwelcome when you just want a little less light at the same color temperature.
The L7-C combines the best of both worlds. The model reviewed had the optional on-board controller. Using a very simple rotary knob you can adjust the intensity of the light from 0% to 100% very smoothly with the exact level displayed on a digital display. At maximum, the most power you will use is 220 W, which is really remarkable. You could quite easily use several of these lamps running off a domestic supply and never come near to the system's maximum capacity. Obviously, the relatively low power use also has a beneficial effect on running costs.
A second rotary knob controls color temperature and this can be varied over a large scale. At the bottom end you can go as low as 2,800 K and at the top end up to 10,000 K. Again, the level chosen is shown on the digital display which automatically changes to show the relevant data for the particular control being operated. The color temperature is shown in steps of 50 K and this means it is incredibly easy to make sure that several fixtures are all set to the same color temperature. It also makes it very easy to match fixtures to the reading obtained from the camera's white balance or a color meter.
The estimated lifetime of the LED unit is quoted as 50,000 hours and the estimated color shift over this lifetime is less than 200 K, a remarkably good performance and the very slight color shift over this length of time is not something I would lose any sleep over.
The third rotary knob under the digital display is plus/minus green, which makes it very easy to match the light with location practicals fitted with less than perfect fluorescent tubes.
I should mention here that there are further L7 models available for those situations when the ability to vary color temperature over a large range is not so important. One model is the L7-T, which is available in both 'hybrid' and 'active' cooling versions with a color temperature of 3,200 K; it is 20% brighter than the L7-C. The other model is the L7-TT (Tungsten Tuneable), which has a color temperature range of 2,600 K to 3,600 K and is 40% brighter than the L7-C. Finally there is also the L7-DT (Daylight Tuneable), adjustable from 5,000 K to 6,500 K and 30% brighter than the L7-C.
The fact that the display on the L7-C shows each parameter (intensity, color temperature, plus/minus green) so accurately makes it easy to take notes as to how exactly each lamp was set up. This is invaluable in situations where you may have to return to a location at a later date and replicate the same conditions as those scenes shot weeks earlier. Two presets can also be stored and recalled in the optional on-board controller.
Unlike a traditional HMI lamp, you don't need a separate ballast to use this lamp. All the components are situated in the lamp housing. The stirrup can be slid along the side of the housing to rebalance the lamp if front-heavy accessories are added.
DOING WITHOUT GELS
So far so good, but the versatility of this lamp isn't just as a replacement for a conventional Fresnel lantern. Just one press of the menu button changes the function of two of the rotary knobs: the 'Color Temperature' control becomes the 'Hue' control, which enables RGB color mixing, while the 'Plus/Minus Green' control becomes the 'Saturation' control, enabling you to alter the saturation of whatever color you've chosen using the 'Hue' control. Again, the display tells you exactly what you've selected. The practical application of this is that you can quite easily dispense with carrying around a large box containing a selection of colored gels.
Not using colored gels has several advantages: it's quicker as you don't have to cut the gel to the appropriate size and find your croc clips to fasten it to the barndoors (producers really appreciate shorter setup times). It's cheaper because you don't need such a large selection of color filters. You can experiment with different colors instantly and at no cost. There isn't a problem with gels rattling in the wind or burning out. You can adjust the color subtly to complement other colors in shot (the talent's tie, props, etc.).
I tried this color change facility when lighting a music video recently. I needed to wash a drape with color and it took only a matter of seconds to achieve the color I wanted. Had I been using conventional lamps plus gels it would have taken a lot longer while I experimented with different gels to get the right look.
The light beam itself is very smooth, as you would expect from a Fresnel lamp of this quality. The lens is 175 mm (7") and the spot/flood goes from 15° to 50°, a useful range for most situations. There are four barndoors supplied (two of them adjustable in size) and so beam-shaping when flooded is quick and easy. The spot/flood adjustment is controlled by a large black knob on either side (non-pole versions) just below the barndoors. Either can be used to adjust the beam angle, with just three turns being required to go from spot to flood. This control alters the angle by extending the lens housing forward and so increases the length of the light.
Although the light has the same familiarity as a traditional Fresnel light, it's also been designed to be relatively future-proof. In addition to DMX sockets there is also a mini USB socket to enable firmware upgrades as and when these become available.
I've always been interested in new developments in lighting but rarely does something so versatile come along. The L7-C is quite simply a game-changer and will no doubt become a standard fixture throughout the industry.