Did they finally do it? LED Fresnels?

[Dan Brockett]

ProVideo Coalition.com: News by PVC Staff

LED Fresnels? I hope so, we have been needing something like this for years.

Dan

[Garrett Low]

Wow! The Sola12 sounds really appealing. Any word on pricing of these lights?

Thanks for the find Dan,

Garrett

[Mark Wheeler]

LED Fresnels have been available for a while and these are from Litepanels. I'll be surprised if they're not a small fortune.

The two most powerful emitters (that I'm aware of) are the XP-G and the SST-90 and it will be interesting to find out what emitters they're using. The CREE XP-Gs max out at approx. 325 lumens each. With nine in a Fresnel fixture (yes, one should soon be available) that'd be just south of 3K in a 90mm form factor while the Luminous SST-90s pump out up to 2.25K lumens... each... but are far less efficient. The SST-90s suck batteries dry pretty fast. The CREE Fresnel that I know about varies from 10 to 60 degrees while the Litepanel blurb claims between 10 and 70 degrees so they may be manufacturing their own Fresnel lens.

Looking forward to seeing one of these in person.

Here's the beam spread from the Fresnel lens for the CREE XP-Gs that I'm aware of:
http://farm5.static.flickr.com/4017/...e23ff95a_o.jpg

[Dan Brockett]

Hi Mark:

Please post a link to an existing LED fresnel that is available to buy. I have seen something called a Komet, but it retailed for $6k and was more like a PAR with multiple larger LEDs, if I recall, it did not have a fresnel lens but that was a couple of years ago that I saw it.

If you notice, these new LitePanels do not include a facility for barndoors and scrims, assuming the picture in the link is a finished product and not a prototype. A fresnel without barndoors or scrims would be pretty useless to many.

Dan

[Dan Brockett]

If history holds true, the two larger models will retail for probably well over $2k and probably a lot more, which relegates them as a niche product, just as HMIs are today. The specs sound interesting and LitePanels makes pretty good products for the most part. I don't think LED fresnels will find mass market acceptance until they are priced roughly at similar levels to the equivalent output tungsten instruments.

Dan

[Richard Andrewski]

Yeah, I'd like the see the existing LED fresnel as well. Its not a fresnel unless it has at least two things: fresnel lens and focusing ability. Otherwise, its just an open faced light which sometimes have ability to focus and many times do not.

No barndoors or scrim/accessory holder on this picture. A lot of people will still want at least the ability to use a half scrim and barndoors for shaping are absolutely necessary if you really are able to give a single shadow. The whole "light shaping" thing is what a fresnel is all about and you can't do that with multiple shadows on the output.

I did some work on this back in 2007 and posted a bit about it here:

http://www.dvinfo.net/forum/photon-m...-lights-2.html

Gave up on it because I don't see at $1000 or greater a very big market. There's no reason to do a fresnel if you can't beat the single shadow issue. That issue alone means you can't use multiple LEDs. And I don't believe that the fresnel lens will save you in terms of faking the single source output. So if you use one high wattage LED, the heat sinking requirements are such that you can't make the traditional light on a sled to do focusing.

Its more like, you have a huge heavy heat sink you mount the high wattage LED on then the front of the fixture goes back and forth on the heat sink. Plus the fact that high wattage LEDs are basically a 2D device means they can't work as efficiently with PAR mirrors. A traditional "3d source" (like a tungsten or hmi bulb) which can be placed in the sweet spot of the PAR reflector works much better. Need a 3d LED basically to do that right in my opinion if you still want to use the traditional mirror to pump up the output efficiency. No mirror or inefficient mirror means you need a better and more efficient LED all alone.

[Mark Wheeler]

This is the Fresnel fixture that I first learned of...

Elation ELED Fresnel - High Power LED White Light Fresnel

Note that this is a (relatively) old fixture that is NOT using the higher power LEDs that are now available (as the Litepanels almost surely are) and puts out 500W tungsten equivalent.

The CREE Fresnel I referred to is not yet on the market.

[Mark Wheeler]

Hi Richard,

Out of curiosity could you share what emitters Cool-Lights is using?

[Richard Andrewski]

Hi Mark,

I doubt many here would consider that Elation fresnel a serious contender for video/film work. Its got a fan in it. Maybe good for disco or theatrical but people would be seriously disappointed for video work. That's the only way however they could make a fresnel in something approaching a normal expectations of a fresnel fixture form factor. Otherwise, the heat sink for a 50w LED would be so big and heavy it just wouldn't work.

If you mean the 60w LED on the previous link I gave, that's made in Taiwan at a company called Domag. I don't consider that or any of the super high wattage LEDs I've seen to be interesting. We've seen 100w ones here in China and they just get far too hot to use in anything other than a street light or where a fan can be used.

[Mark Wheeler]

You're a lot closer to the source then I'll ever be and your input is fascinating. A lot of issues surrounding LEDs that the consumer neither knows about nor... presumably... cares. Given the amount of lumens that Litepanels is pumping out it will be most interesting to get your input on their design.

Take care.

[Richard Andrewski]

Right, will be interesting to see what they did and how. Things I would want to know if I was going to NAB (unfortunately I can't make it) would be:

Price?

Does it have a fan?

Why no barndoors or accessory holder (perhaps that's just a picture of an early prototype and final model will have).

What kind of LED(s) inside? Single, multiple?

If multiple, how did they lick the single vs. multiple shadow issue.

If single and doesn't have a fan, how did they do without the large heatsink?

Etc.

[Paul Curtis]

I've played around with LEDs and CREEs etc,. Some of those high power crees have 4 LEDs on the same chip and through the use of dedicated optics (that you place over the optics already part of the LED) you can merge the separate sources into one via diffusing or focusing the 4 together. However that only works for a certain angle - not focusable. Same for the SSTs which are basically an array of LEDs close together - so that's not a point source either.

They have to be using multiple LEDs inside there for that output, so the question is how are they claiming a single point source shadow?

About the only thing i can imagine is a custom reflector design and lens designed to focus the point sources into one which is then focused again. Perhaps something like the dedo aspherics system with multiple lenses. I gave up trying to work out reflector designs that would work. Sadly i have a day job!

I would love to see what they're up to, it's a holy grail really.

Can someone at NAB accidentally knock one over and see if you can get inside the case? :)

cheers
paul

[Bill Hamell]

Originally Posted by Paul Curtis

They have to be using multiple LEDs inside there for that output, so the question is how are they claiming a single point source shadow?


paul

A Tungsten Fresnel has two light sources, the bulb and the reflector just as an openface light does; the lens focuses these two light sources into one light source thus a single shadow. Therefore, whether you have two light sources or ten in a Fresnel you get one light source and a single shadow.

Bill

[Richard Andrewski]

There are differences. The two light sources you speak of are perfectly aligned one in front of the other and work well to make one source. The bulb and mirror alone aren't efficient so we add the lens.

Where the differences come in this case, an LED is not a bulb, its a miniature spotlight or fixture in and of itself. A bulb by itself has no projection capability other than radiating light 360 degrees around it. The mirror helps make the bulb into a fixture thus giving it a beam and projection capability. The lens completes that by magnifying a bit. Put 2 or more LEDs behind the lens and you have a bunch of spotlights projecting through a lens but should still each give its own point of light. Space them as closely as possible to each other but its still multiple sources of beams. Since the LEDs radiate mainly forward, a mirror behind them wouldn't help much. Without diffusion in the lens, it doesn't mix into one source, its just several sources trying to go through a lens and still coming through a bit as several beams. Add diffusion to the lens to try and blend them and you lose the hard shadow rendering capability we expect from a fresnel.

Would definitely be an interesting experiment to try.

[Bill Hamell]

In other words, the lens is designed for the application. When using LEDs you need to redesign the lens to match the new application, which is what I believe that company has done, or they figured out a work around with Fresnels design.