Litepanels Solas

[Christopher Barrett]

I'm really curious about these Litepanels fresnel like units. I don't believe they're shipping yet, but wonder what others think of their design? The idea of a highly dimmable daylight balanced light that actually throws is really enticing. I also wonder about the light quality. I assume these have to have a much softer effect than tungsten or HMI fresnels... I would LOVE to have something with the effect of a soft box that would throw light across a room AND be controlled with flags and doors.

Hmm...

 

[Guy Bryan Holt]

I'm really curious about these Litepanels fresnel like units. I don't believe they're shipping yet, but wonder what others think of their design?

I have been following the development of the Sola Fresnels with interest. While they are definitely a step in the right direction in developing a production LED light, they still don’t quite combine the advantages of LED illumination (cool-burning, energy-efficient) with the versatility and control of traditional Fresnel fixtures. If the history of film style Fluorescent lighting offers any lessons, the manufacturers of High Power LEDs will have to address several key issues before LED lighting can replace incandescent and HMI lamps in studios and on location sets powered by generators (particularly small portable generators.) For LEDs to be widely used, manufacturers must overcome their poor color rendering, poor power quality, and lack of versatility. Progress is being made, however, on many of these fronts.

The OSRAM Kreios stage light LED module ​

Until the recent development by OSRAM of their KREIOS® LED technology, the color rendering of LED fixtures was generally pretty poor (use this link - http://www.oscars.org/science-technology/council/projects/ssl/index.html - to the Academy of Motion Picture Arts & Sciences’ “Solid State Lighting Project” for details.) The new OSRAM KREIOS® stage light module (pictured above) uses remote phosphor technology to produce light in two exact color temperatures, Tungsten and Daylight. While, remote phosphor technology has been used for years to extend the short wavelength of Blue LEDS to create a fuller color spectrum, OSRAM was the first LED manufacturer to use remote phosphor technology to exactly match the spectral sensitivity of Tungsten and Daylight balanced film stocks. Unfortunately, the new OSRAM KREIOS® stage light module is only available in the Mole LED 12 Pack light panel (use this link for more details.)

A second problem inherent in LEDs that manufacturers will have to address is the relatively poor power quality generated by the Switch Mode Power Supplies (SMPSs) they use to power their lights on AC power. The SMPSs used in LED AC power supplies can draw a very distorted current, and result in current that is significantly phase-shifted with respect to the sinusoidal voltage waveform. Although values vary widely, the SMPS used in the AC power supplies of LEDs generally have a Leading Power Factor around 0.54 (Litepanel 1x1s) and high harmonic distortion (THD upwards of 68.1%). As such, the AC power supplies of LEDs can have an adverse effect on power quality similar to that of CFLs (use this link for more details.)

Finally, before LEDs will be widely accepted in motion picture production, manufacturers will have to engineer a fixture that has the versatility and control of traditional Fresnel fixtures. The drawback to existing LED light panels is that their light falls off very rapidly and is hard to control. These characteristics make LED light panels only suitable as Key sources in documentary interview set-ups where the Keys are typically positioned close to the interview subject. In that capacity LED light panels (with heavy diffusion) can generate a wonderful soft light that wraps around the interview subject without wilting them. However, in dramatic set lighting, where Key sources must be capable of throwing a distance, LED light panels have only limited applications as fill sources. The broad soft light they put out drops off too rapidly, and is too difficult to control, for them to be effective as a Key or Backlight source in dramatic set lighting.

As far as I am concerned, Litepanels has not overcome these problems with the Sola fixtures. Litepanels doesn’t give CRI ratings for the Sola Fresnels on their website, but when asked they say the CRI is in the 80s – which is still rather anemic compared to other light sources. The Power Factor of the Sola has been improved. But, at .85 it could stand further improvement (a Power Factor Corrected HMI has a Power Factor of .98 or near unity power.) They claim the 75W Sola 6 has the output equivalent to a 650W Tungsten, but comparing the photometrics published on their website to those of an Arri 650 Fresnel, the Arri has nearly three times the output of the Sola. And, while the Sola 6 has an impressive spot to flood range (10 to 70 degrees), spot/flood capability is not the only characteristic that makes a Fresnel light versatile. Of equal importance is the ability to render clearly defined shadows and cuts. The ability of Fresnels to render crisp shadows make them ideal for creating gobo effects like window or branch-a-loris patterns. The ability of Fresnels to render clearly defined cuts enables their light to be precisely cut to set pieces and talent. And, simply by adding one of a variety of diffusion material you can vary the softness of a Fresnel’s output. These are the characteristics of traditional Fresnels that make them extremely versatile, that the Sola “Fresnels” have not been able to emulate.

However, progress is being made in the development of a true LED Fresnel. In September 2010, Arri introduced a prototype for their L-Series LED Fresnel at the European trade show, IBC 2010. As is evident in a demo video that was recorded at the show (available at www.screenlightandgrip.com/html/emailnewsletter_generators.html#anchorLED%20Fresnel ), Arri may have finally engineered a fixture that combines the cool-burning, energy-efficient advantages of LED illumination with the controllable versatility of traditional Fresnel fixtures. Not only is the beam of the Arri L-series Fresnel continuously focusable from spot to flood; but it is also easily controlled with barndoors and flags. Just like conventional Fresnels, the light of the L-Series Fresnels can be precisely cut to set pieces and talent. And, while CRI ratings are not available (the L-Series Fresnels are still in the prototype stage), Arri promises on their website “broad spectral output (such that), skin tones, costumes and scenery will appear vivid and lifelike.” With the clear and defined shadow rendering, excellent field homogeneity, and smooth continuous flood to spot focus demonstrated in the IBC 2010 show video, Arri may have engineered the first true LED Fresnel. And, if they can deliver on their promise of “broad spectral output”, Arri may well have the first true production LED light (use this link for more details.)

For more detailed information on the Power Quality generated by LED power supplies and to see the demonstration video of the new Arri L-Series LED Fresnels, use this link to an article I wrote for our company newsletter on the use of portable generators in motion picture lighting. In it I cover some of the basic electrical engineering principles behind LED drivers, the harmonic distortion they can generate, and how it can adversely affect generators. This article is cited in the just released 4th Edition of Harry Box's "Set Lighting Technician's Handbook" and featured on the companion website "Box Book Extras." The article and video are available online at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html.

Guy Holt, Gaffer, ScreenLight & Grip, Lightng & Grip Rental in Boston

In the interest of full disclosure I should mention that we sell and rent Arri products along with the products of most major manufacturers of lighting and grip, and Honda portable power generation equipment.