PAR LED

[fincaman]

Hello all, I am thinking of buying some PAR 56 LED cans. I already have some very cheap 151 led stairvilles which are quite good for what they are but I want something a bit more meaty. I have been looking at some 36 X 1w and wondered how they compare with standard PAR 56 cans. Is there a rule of thumbs formula to calculate the brightness of LED's I have seen information that said it's X 8 or X 5 i.e. 36w led X 8 = 288 w tungsten lamp. Is this correct ?

 

Regards

 

Kevin

[Brian]

I've got some 36 x 3W units which on colours are as bright as 1k PARs. Not on white though. So I'd reckon that some 36 x 1W units will match 300W PAR56s on colours.

[Ashley R]

Ive never heard of a formula for working out the comparison between LED and regular Par cans, as the intensity of the LED's varies just that much, its just impossible to do. Just something that comes with trying them and seeing the LED fixtures in real life.

 

a 36x 1w Should be equivalent to a 300w PAR 56, although I would go with something that has TRI LED's in it as that gives much much better colour mixing than separate LED's

[adam2]

There is no exact equivalent, it varies a lot both according to the qaulity of the LEDs and as to what colours are selected.

 

LEDs are very much brighter than filtered halogen lamps for deep saturated colours.

A 36X3 watt LED PAR on 100 % blue can be as bright as a 1KW halogen with congo blue filter.

A similar LED PAR on white is unlikely to equal 300 watts of halogen on open white.

 

For fixed building lighting, not theatre, I replaced 150 watt blue filtered halogen lamps with 10 watts of blue LED.

The LEDs were much brighter,

[Don Allen]

it is a rather subjective evaluation that can only be done with a side by side comparison or "shootout". I did my shootout using a Selecon Axial Acclaim profile which with a 600W lamp is equal to a lot of 1K profiles, a Strand Patt 223 with a medium to wide beam spread and a LED Emperor 48 x 5W RGBA LED Par.

 

You are looking at two different processes as tungsten halogen lights are a subtractive process with the gels, so a lot of their full spectrum white light is dissipated as heat in the gel. Using Lee 164 Flame red as an example, which is in the usable range of reds for musicals etc, the Y or luminence pass figure is 18% so for a 1K light source you get 180W of red on the stage. The beam angle of the lens will spread this available light out, or concentrate it. The 223 and the LED Emperor were side by side, about 2 metres from the stage, the profile was about 5 metres from the stage.

 

The LED Par's are an additive process so the 12 x 5W red LEDS and most of the 12 x 5W amber LED's provide 120W of 38 degree light on the stage. The reason why I paid the extra and bought RGBA was to get as much LED colour as possible on the stage. I was also using Light factory 2 to control the LED Par's as the personality that Enttec wrote for the ETAN LED Emperors uses as much of the four colours available to give as close a spectrum match as possible. Plus there is the colour selectors and Lee swatch selector to speed up plotting. Also remember that a LED's colour is a very narrow spectrum and will affect costumes, sets etc so always check beforehand, do not leave it untill the show to discover that you have altered the costume or set colours for them. (Sometimes you do this deliberately but with planning.)

 

I used an Altronics Lux Meter to take comparitive measurements to reinforce my "gut" feeling. Note that a budget lux meter cannot be used for any accuracy. The LED Par's "red" was brighter that the other fixtures by about 20%. Visually, they looked the same.

 

My LED Par's will never replace an open white tungsten source, but I use them as a compliment to provide a flexible colour source. The dialogue lighting was done with soft blues and pinks tungsten fixtures. The poor dimming curve at the bottom end was not noticeable with the musical cues and the fan noise was not heard as it rained for most of the season.

 

So you can find LED replacements to make lighting easier, but some of the compromises include budget, colour rendition, dimming curve, reliability etc. I am a tech which is needed when trying to get cheap fixtures as I had to do some work on them. Do your homework and get a side by side shootout.

 

My next experiment which will hopefully arrive tomorrow are 84 x 3W RGBW wall washers to try out a cyc lights.

[fincaman]

Ive never heard of a formula for working out the comparison between LED and regular Par cans

 

Lots of people that advertise led lamps will say things like 3w LED lamp equivalent to 24 w normal lamp

 

it Do your homework and get a side by side shootout.

 

 

I can't I am in Spain and have to buy everything mail order I just want advice what should I buy that is broadly similar to a par 56 I only have to light a very small portable stage

 

Regards

 

Kevin

[Brian]

Lots of people that advertise led lamps will say things like 3w LED lamp equivalent to 24 w normal lamp

And they are always the people trying to sell you LED fixtures.

[vinntec]

... and the fan noise was not heard as it rained for most of the season...

I used 10 x LED PARs for backlighting West Side Story recently and they were brilliant for the deeper close-to-primary colours as others have already said. However I was surprised to find fans in them as, despite heavy use, they seemed to be running absolutely stone cold (unless you got real close to the front of the LEDs). I was just wondering what the technical reason is for having the fans?

Peter

[Don Allen]

Excerpt from Luxeon Star Knowledge Base :

"All high power LEDs produce heat that needs to be dissipated in order to ensure that the LED junction (the part of the LED that actually generates light) is kept well below it's maximum operating temperature. If the junction temperature is allowed to get too high for too long, the overall life of the LED will be significantly shortened, the light output from the LED will be reduced, the color output of the LED could vary, and in a worse case scenario, the LED will simply fail.

 

Heat is typically removed and dissipated from the LED using some sort of heat sink or heat sink/cooling fan combination; the size and shape of which will depend on:

The wattage rating of the LED.

The number of LEDs you are powering.

The temperature of the environment the LEDs are operated in.

Whether the LED is mounted in an enclosed or open space."

 

If you do not want fan noise, then use outdoor LED lights as most are sealed so do not use fans. They are lower power so the LED junctions do not get as hot and rely on the fixture body to dissipate heat.

[musht]

I was just wondering what the technical reason is for having the fans?

 

 

LEDs suffer a serious temp realted efficiency problem, hotter they get , dimmer they get, as well as affecting life time.

 

Fans are generally cheaper than blocks of alloy, think cheap disco power amps, sound like a jet engine as fan cools barely adequate heatsink.

[dbuckley]

Heres what's inside a Chinese sourced LED PAR, with 24x1W RGB LEDs; the LEDs are mounted to the right of the heatsink.

 

http://davidbuckley.name/pix/led_inside.jpg

[bigclive]

The difference between a passively cooled heatsink using convection to move air, versus a fan cooled heatsink with forced air is vast. LEDs have a relatively low tolerance to heat, so a high power array really needs forced cooling to keep it at a safe temperature.

[vinntec]

I used 10 x LED PARs for backlighting West Side Story recently and they were brilliant for the deeper close-to-primary colours as others have already said. However I was surprised to find fans in them as, despite heavy use, they seemed to be running absolutely stone cold (unless you got real close to the front of the LEDs). I was just wondering what the technical reason is for having the fans?

Peter

Thanks everyone for the clarification about why fans are essential - Peter