Arri L7-C Color LED Fresnel

[Yousuf Abbasi]

Anyone used these badboys in a project? Read the specs, looks like it could be a compact yet versatile lighting solution. At a $3K pricetag, anyone think its worth it?

Would you use it for hard and soft lighting? I love 1-stop-shops... hoping this could be one, for lighting.

http://www.arri.com/l-series/features.html

 

[Bob Gruen]

Haven't used one, but it is a simple true-ism that you can soften hard light, but not vice versa. Soft light in the small scale is cheap (Kinos), but going medium to large always involves softening a large hard light. So the models that throw more than a Kino are 'worth it'.

BTW, I'm dying to open one of these up just to see how they did it. I'm guessing they mounted the LEDs on a curved surface that behaves similar to the curved mirror in a traditional fresnel.

LEDs and plasma will most likely be the small the medium scale solutions going forward. Lots of lumens with low power draw and heat are the panacea of filmmakers everywhere.

Bob

 

[Ramesh Jai]

I ordered some a couple of weeks ago and am still in the waiting line. I'm told they have 8-12 weeks delivery times.

 

[Maz Mawlawi]

Just keep in mind that they are only equivalent to about a 200w HMI... (or 650 tungsten)

 

[Ulf Krentz]

snip

BTW, I'm dying to open one of these up just to see how they did it. I'm guessing they mounted the LEDs on a curved surface that behaves similar to the curved mirror in a traditional fresnel.

snip

Bob

Probably not, LED / Plasma won´t send light backwards, so no need for a mirror or a curved shape. The shape of the mirror is only curved to reflect the light back to the emitting lamp. The fresnel lens should only "see" the filament and the mirror can be adjusted to achieve this.
I´d like to hear about color rendering, especially with skin tones, anyone?

Cheers, Ulf

 

[Peter Berger]

I'm dying to open one of these up just to see how they did it. I'm guessing they mounted the LEDs on a curved surface that behaves similar to the curved mirror in a traditional fresnel.

Its a common misunderstanding that the reflector of a Fresnel light collimates light as Bob Gruen suggests. According to Guy Holt’s very informative article on LEDs and the L7, the purpose of the reflector in a quartz Fresnel is, in fact, to double the intensity of its' output by creating a mirror image of the lamp’s filament. When the light-emitting filament of the bulb is placed near the center of curvature of a spherical, concave polished mirror reflector, the reflecting surface creates an image of the filament. That image is located on the same plane, but slightly displaced from the filament itself. This has the effect of doubling the amount of light forward projected from the locale of the lamp filament while maintaining the point source quality of the filament, which is very important to achieving the quality of light characteristic of a Fresnel lens.

According to this article there are two big hurdles to manufacturing a LED Fresnel head of a practical size - say, the equivalent of a 650W Tungsten Fresnel. First, Fresnel lenses require a point source of light. Second, they are not very efficient and so require a lot of light. Unfortunately, at this time there is no single-diode LED with sufficient output to serve as a point source for a Fresnel lens. How Arri is able to accomplish the characteristics of a true Fresnel from a multi-emitter array is by using a simple lens system consisting of a Condenser Lens with an extremely short focal length. The Condenser Lens focuses the output of the LED Array into a point source.

By moving a Fresnel lens forward and back in relation to this assembly of LED Array and Condenser Lens, the focal point of the Condenser lens moves in relation to the Fresnel lens much like the lamp/reflector assembly of a traditional Fresnel Head. This has the effect of spotting and flooding the light output of the LED Array much like a Fresnel spots and floods the output of a point source (use this link for an illustration of this system and the color rendering of LEDs.)

Peter Berger

 

[Michael Tiemann]

Just keep in mind that they are only equivalent to about a 200w HMI... (or 650 tungsten)

Looking at the photometric data (foot candles at 4.6m-5m, 30 degree medium beam), it's closer to the 300W unit than the 650W unit. What gives? I thought these were supposed to replace 1KW instruments!?

 

[Yousuf Abbasi]

Anyone got delivery of one of these yet? I want to hear field experience.

 

[Mark K.]

For the money, I reckon something like the Photon Beard Nova 270 is a more interesting prospect at this stage.