How Can LEDs Compete with HMIs on Set?|
Article - January 18, 2016 By LarsonElectronics.com
How Can LEDs Compete with HMIs on Set?
On movie sets, producers have a plethora of lighting technologies at their disposal. Currently, hydrargyrum medium-arc iodide (HMI) lamps dominate the industry as the lighting option of choice. They are known for generating incomparable, intense light beams that other types of fixtures simply can’t match. However, there is another type of light that many professionals are raving about: light-emitting diodes (LEDs).
LEDs are the latest breed of luminaries to enter movie sets. The fixtures are energy efficient, bright and compact. With LED technology reaching new milestones in development, what would it take for the units to surpass HMIs during filming?
Out of the two types of filming lights, HMIs offer more accurate color rendering features. This was tested in a report titled Full Spectrum of Light Sources Compared with LED Fixtures. The trials involved comparing the two technologies using spectrophotometry. During operation, HMIs produce a continuous spectrum, with spikes in green and emphasis on the blue spectrum due to the light’s high color temperature rating between 5,500K-6,000K. The spectrograph of a “white LED” does not appear as smooth. The blue spectrum fluctuates from bright to dark near violet bands, because of the way “white LEDs” generate white light. It uses blue and violet diodes with phosphorus coatings to activate other areas of the spectrum (green, yellow and red). This can make some yellow objects appear slightly green, red objects appear slightly pink, brown objects appear darker and orange objects appear lighter.
In the filming sector, accurate color rendering is essential. High-powered cameras can easily pick up inconsistencies in lighting, color depictions and other minor flaws in the shot. With that in mind, LEDs must be able to offer better color rendering features in order to fill the role of HMIs on the set. Currently, there are high quality LEDs on the market with superior color rendering ratings. They are typically found in paint spray booths that require precise color-matching and accurate color rendering features.
HMIs are noticeably brighter than LEDs. As a result, in order for LEDs to compete with HMIs, they need to be able to generate (at the very least) the same level of light output. HMIs produce light differently, compared with LEDs. They rely on discharge technology, which heats up an arc inside the bulb to extremely high temperatures with help from an electronic ballast. LEDs use small, powerful chips to create light via electroluminescence. The fixtures offer directional lighting conditions, and require newer manipulation and design techniques to control the beams on the set. By comparison, HMI bulbs emit light in almost all directions. The luminaries utilize reflectors around the bulb to direct light to the target area. When it comes to the quality of the beam, both types of lamps are capable of emitting high color temperature ratings- as high as 6,000K.
Advantages of LEDs
In some aspects, LEDs have already surpassed HMIs. The latter does not support instant toggling, and must be warmed up for roughly 10 minutes before reaching full light output. It also needs to be cooled down when turning the light off and on again from an operational state. By comparison, LEDs support instant toggling. Rapidly turning the light on and off does not affect its lifespan. The lifecycle of the fixtures also varies greatly, with LEDs lasting 50,000+ hours in optimal environments and HMIs averaging 600 hours of operation. HMIs have a complicated lifecycle, because they should never be fully depleted. It is common practice to replace HMI bulbs at 50 percent of its lifecycle. This is done for two reasons: (1) HMI light quality degrades slowly over time, (2) straining HMIs can result in explosions, causing bits of hot quartz glass to spread around the set.
LEDs are also more compact, and can be used in remote sets using battery-powered variants. Moreover, they emit very little UV light, because the amount that is generate during operation is converted to white light via phosphor compounds inside the fixture. HMIs produce high levels of UV light, and require special covers that block harmful rays. Long-term exposure at close ranges may cause damage to one’s retina and lead to skin burns. LEDs are highly energy efficient and do not heat up to extreme temperatures. Because of this, workers can handle the lights without thick gloves.
Playing Catch Up
LEDs are steadily closing the gap in the race to compete with HMIs. In application, movie sets incorporate different types of lights, depending on the needs of the shot. For example, LEDs are favored by low budget producers and are used for small sets. They also perform well in remote sets with limited access to power. In some cases, LEDs can be utilized in tandem with HMIs, with the latter providing most of the lighting and LEDs highlighting smaller components on the set.
From a cost perspective, both types of lights are expensive. However, LED prices are decreasing consistently, as researchers develop the technology and manufacturers find new ways to cut costs without affects the quality of the product. HMI prices are generally expensive and will likely remain that way in the future, because there hasn’t been any significant advancements in the development of the technology. The fixtures also come with fluctuating maintenance and replacement costs, which could add up for sets with multiple HMI lamps.
For now, HMIs still reign over the film sector and will continue to for some time. But LEDs have a reputation for out-doing traditional lighting technologies that at one point, were considered to be the industry standard, such as incandescent and fluorescent luminaries. If the development of LEDs continues to proliferate at its current pace, it may one day surpass the capabilities of HMIs on movie sets.