Tungston vs LED Query

[michaelyallop]

Hi all,

 

I've been pondering this for a while and have done multiple search's and research in these magical things called books, but haven't been able to answer this question. This is one for all you physics type people out there.

 

So here goes. An LED lamp, say a Parcan has the equivalent light out put as a Tungston Parcan, 1K for instance. To the naked eye they both have a perceived equivalent light output, however stick some smoke in the air and the LEDs fail to cut through as much as the Tungston lamps. This seems to be the case if you use the any colour, ie LEE filter 106 primary RED on both lamps, the LEDs don't seem to cut it.

 

I know that Photons are supposedly massless unless trapped in mirror box where they will slightly increase the mass of the box and that E=mc2 doesn't really apply to the movement of particles as it is a stationary formula.

 

Can anyone shed some light, pun 100% intended?

 

Thanks.

[timsabre]

I am not sure what you mean by "LEDs don't cut it" but assuming you are talking about visibility of the light beam in the air, in my opinion this is just down to beam angle / beam control.

 

The output of a tungsten parcan is a well defined beam which shows up well in smoke.

A lot of LED parcans have much more light scatter around the main beam, and softer edges to the beam, which in smoke looks a lot less dramatic and more wishy washy.

 

(putting colour filters on LED fixtures is a whole other discussion, but probably not part of this)

[ABlackmore]

Timsabre's pretty much covered the smoke part, so I'll try to cover the gel issue as simply as I can!

 

Assuming you're referring to LED lamps of equivalent native temperature to tungsten lamps it's partially to do with the fact that tungsten halogen lamps are full spectrum sources whereas LEDs are not. This is why high CRI (or more importantly TLCI if you're working in TV/film) sources are preferable as they cover more of the spectrum. Take a chunk out of that spectrum with a coloured gel (keeping in mind gels are subtractive) and you run the risk of increase the relative loss of spectrum when compared to a tungsten source (depending on where the LED in questions dips and spikes fall).

 

Of course most LED sources are natively closer to daylight on the spectrum, rather than tungsten - in this instance a tungsten heads natural curve puts it far closer to your 106 naturally, blocking out the 'blue' part of its output will result in a comparatively negligible loss of light when compared to the loss of putting said gel on a daylight balanced LED source. You can see this just by comparing the transmission rates of gels between daylight and tungsten sources on most of the gel manufacturers websites (Lee have a particularly good tool).

 

http://www.screenlightandgrip.com/images/generators/LED_Comp_Sprectrum.jpg

[timsabre]

That's a great explanation of the gel issues. We should put all this stuff in the LED section of the Blue Room wiki, which as someone pointed out yesterday is woefully lacking in relevant information.

[ABlackmore]

Thanks haha, there are technically a couple of oversimplifications in there but it should be enough for a 'working explanation'. I'd be more than happy to put it in the wiki if people are in agreement - though I'm sure others would be able to add to it!

[musht]

An LED lamp, say a Parcan has the equivalent light out put as a Tungston Parcan, 1K for instance.

 

1K CP62 ( Colour Photography 3200k) Par 64 outputs around 138,000 Centre Beam Candle Power out of an 8" circle, most of which goes out front.

 

1K LED array will be larger than 8".

 

Power density in a collimated beam appears brighter.

 

Parabolic Aluminised Reflector lamps are a suprisingly efficient design even now.

 

edited to remove lumen confusion

[michaelyallop]

Sorry, I should have explained myself a little more. I don't put Gel in front of LED lamps, just use the colour palette to sellect the LED mix colour of the primary red, but obviously do stick a Gel in front of the Parcan.

 

Thanks for that info ABlackmore really informative and as tinsabre has said maybe it needs adding to the wiki.

 

Again Thanks timsabre for your input, I do get your point about harder edges etc. With our lamps its not just the edges that seem to be cut out but the entire light source. A Parcan just cuts through.

[ABlackmore]

Sorry, I should have explained myself a little more. I don't put Gel in front of LED lamps, just use the colour palette to sellect the LED mix colour of the primary red, but obviously do stick a Gel in front of the Parcan.

 

Thanks for that info ABlackmore really informative and as tinsabre has said maybe it needs adding to the wiki.

 

Again Thanks timsabre for your input, I do get your point about harder edges etc. With our lamps its not just the edges that seem to be cut out but the entire light source. A Parcan just cuts through.

 

Musht's comment regarding the surprising efficiency of parabolic reflectors is also fairly relevant, their ability to 'project' is really quite phenomenal given the age of the design and will out perform quite a few of the lower tier LED parcans in terms of projection. As musht's comment rightly implies this is because they're technically more of a point source than an LED array is. Sure the lamps LOOK huge, but all that light is coming from a relatively small area (the filament) and is being projected by the parabolic reflector. Compare that with cheaper LED arrays and you have a larger source (there are of course some tiny high power LED designs out there, but I'm assuming we're talking the cheaper kind made of many diodes here).

 

A larger source (aka one effectively made up of multiple points) won't, generally speaking, throw as far as a single point source with equivalent power. Combine that point source with a parabolic reflector and lower tier LED pars will struggle to compete in terms of beam sharpness and projection. Of course, where they struggle in that regard they gain fantastic ground in terms of efficiency and convenience!

[musht]

Power density is what makes a laser of a few miliwatts appear bright in hazy air.

 

Beam lights like Aircraft Landing Lights, ACLs use a low voltage filament, low voltage means shorter, curled into center spot of the parabola means that most of the light gets delivered out the front in a near paralell beam, they appear very bright.

 

Why 120V PAR 64s in series were popular, smaller filament , more light going direction its wanted.

 

Current LED technology builds higher power by building arrays of smaller LEDs, effectively 5W about as big as currently get a single dice, so high power outputs mean a large array size, get back to the paralell bean requires corrective optics, efficient binned LEDs and well made optics add cost.

 

Short answer is it dosen`t cut through because it isn`t as bright and Watts is a measure of power consumption not light output ;-)

[Don Allen]

The parcan is a very efficient beamlight when compared to the LED "parcan" which started out as an array of lots of 10mm leds, then evolved into it's most common form of about 18 (typical) led emitters, each emitter with their own individual lens. Each lens has a beam angle of typically 25 degrees, to try and emulate the halogen parcan, and a field angle much wider, about 50 degrees. With typically 18 lens overlapping, there is a lot of spill or difusion occurring, so you will not see the hard edge that a halogen parcan has.

 

Most people accept the term led parcan, as they have a typical beamwidth of 25 degrees to copy a MFL or medium flood parcan, but it would be more correct to call a led "parcan" a led washlight or a led fresnel, due to the soft difused beams. The newer COB led parcans with a single emitter array in the centre are the closest to a led parcan, but most COB led parcans have a beam angle of sixty degrees, as there is no lens, only a reflector. You can get narrower beam angle lens to fit in front of a COB led parcan.

 

The limited spectral response of a led makes it very hard to use a cheap light meter to try and match the intensity levels of a halogen parcan with a led parcan. It is usually a subjective comparison of brightness which makes accuracy dificult.See LED testing

 

It is hard to pick the beam angle and field angle of a halogen parcan in smoke as there is difusion from the main beam that tends to scatter through the field beam so cannot see an obvious edge.

[DNT]

Hi all,

 

I've been pondering this for a while and have done multiple search's and research in these magical things called books, but haven't been able to answer this question. This is one for all you physics type people out there.

 

So here goes. An LED lamp, say a Parcan has the equivalent light out put as a Tungston Parcan, 1K for instance. To the naked eye they both have a perceived equivalent light output, however stick some smoke in the air and the LEDs fail to cut through as much as the Tungston lamps. This seems to be the case if you use the any colour, ie LEE filter 106 primary RED on both lamps, the LEDs don't seem to cut it.

 

I know that Photons are supposedly massless unless trapped in mirror box where they will slightly increase the mass of the box and that E=mc2 doesn't really apply to the movement of particles as it is a stationary formula.

 

Can anyone shed some light, pun 100% intended?

 

Thanks.

 

 

 

 

 

I would not be good on the physics, but from having had years of experience with parcans, and now having tried out a number of LED "equivalents", my observation is that although you get plenty of light, there is a lack of brilliance from LEDs. In general, they are great for saturated colours (and in my experience, still show through haze or smoke), they don't light up the stage in the same way as real parcans do. On the plus side, however, you can get great colours on the red/blue side of the spectrum with most of them. I have yet to see one that gives a satisfactory amber/yellow, but I am waiting to get my hands on an ETC colorsource Par, which promises to deliver in that area, including giving good pastels. I still augment my LED rig with real parcans for the colours I really need for whatever show I am doing, while enjoying the variation the LEDs give me elsewhere in the show. I look forward to even better versions as the technology improves, and some day, I might consider lighting faces with LEDs.

 

 

 

 

Denis

[michaelyallop]

The parcan is a very efficient beamlight when compared to the LED "parcan" which started out as an array of lots of 10mm leds, then evolved into it's most common form of about 18 (typical) led emitters, each emitter with their own individual lens. Each lens has a beam angle of typically 25 degrees, to try and emulate the halogen parcan, and a field angle much wider, about 50 degrees. With typically 18 lens overlapping, there is a lot of spill or difusion occurring, so you will not see the hard edge that a halogen parcan has.

 

Most people accept the term led parcan, as they have a typical beamwidth of 25 degrees to copy a MFL or medium flood parcan, but it would be more correct to call a led "parcan" a led washlight or a led fresnel, due to the soft difused beams. The newer COB led parcans with a single emitter array in the centre are the closest to a led parcan, but most COB led parcans have a beam angle of sixty degrees, as there is no lens, only a reflector. You can get narrower beam angle lens to fit in front of a COB led parcan.

 

The limited spectral response of a led makes it very hard to use a cheap light meter to try and match the intensity levels of a halogen parcan with a led parcan. It is usually a subjective comparison of brightness which makes accuracy dificult.See LED testing

 

It is hard to pick the beam angle and field angle of a halogen parcan in smoke as there is difusion from the main beam that tends to scatter through the field beam so cannot see an obvious edge.

 

 

Great. This is sort of the route I had gone down after the replies above. In essence they are 18 separate 10watt lights/lamps cobbled together to make a Parcan shape. Therefore the light level from a single source is not as bright as an incandescent. I'm not sure why I didn't see this a little earlier.

 

 

I'm not sure why they weren't called LED fresnels or wash lights, maybe due to the lack of lens. I really like them as wash lights and the range colours you can get are fantastic, but they definitely are not a Parcan replacement, unless a COB replacement was designed for the current incandescent parcans. I suppose this would be limited to a single as colour COBs are a single LED.

 

 

I would really like to try the more high end LED lighting such as the ETC profiles etc. Just to compare those to there counterparts.

 

 

 

Mick

 

 

[timsabre]

I'm not sure why they weren't called LED fresnels or wash lights, maybe due to the lack of lens. I really like them as wash lights and the range colours you can get are fantastic, but they definitely are not a Parcan replacement, unless a COB replacement was designed for the current incandescent parcans. I suppose this would be limited to a single as colour COBs are a single LED.

 

Not so, you can get RGB and RGBW COBs. They just put different colour emitters down when they are making the LED. The only problem is the colours are usually in rows which can give some colour fringing on the output beam.

COB fixtures do give a different beam quality to the multi-emitter fixtures but they are still not the same look as a par can in my opinion. They work a lot better with barndoors though.

[michaelyallop]

I'm not sure why they weren't called LED fresnels or wash lights, maybe due to the lack of lens. I really like them as wash lights and the range colours you can get are fantastic, but they definitely are not a Parcan replacement, unless a COB replacement was designed for the current incandescent parcans. I suppose this would be limited to a single as colour COBs are a single LED.

 

Not so, you can get RGB and RGBW COBs. They just put different colour emitters down when they are making the LED. The only problem is the colours are usually in rows which can give some colour fringing on the output beam.

COB fixtures do give a different beam quality to the multi-emitter fixtures but they are still not the same look as a par can in my opinion. They work a lot better with barndoors though.

 

 

 

Ah right, ok. I haven't seen a multi colour COB advertised before. Thanks. I'm guessing they still have a perceived brightness better than the 18 by 10watt multi LED lamps.

 

 

This subject has been something I have been pondering about for a while. I'm quite enjoying the discussion.

 

 

Thanks for the input.

 

 

Does any one know of any COB parcans/washlights with a fairly decent price?

 

 

[timsabre]

This is what a typical 40W RGBW cob looks like. You can see how all the colours are grouped together....

http://sc01.alicdn.com/kf/HTB1oayGLVXXXXbSXXXXq6xXFXXXU/high-power-COB-LED-40W-rgbw-led.jpg