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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Lighting Forum => Topic started by: Tim Hite on October 09, 2019, 03:07:41 am

Title: How to best 'right size' lights?
Post by: Tim Hite on October 09, 2019, 03:07:41 am
Looking to pick up some LED PAR fixtures and trying to make sense of all the offerings and where I need to jump in. Looking at wattages since the China lights don't really have photometric stat and I really don't know how to envision nit and lux ratings properly due to lack of experience.

I'm currently needing to pick up 8-12 IP65 RGBWA+UV wash luminaries for use as a downstage wash. lights will go on truss totems 3m with T bar or 13fft crank stands also with t bar, I'm undecided as to which at this time.

So what's the best way to figure out how much power/light/watts/lux I need to light a performer on an outdoor stage at night from various distances?

Should I be looking at the 200w COB Cannon style lights at all?

I feel like some of the bigger light options in my budgetary reach could be blinding to performers. I'l initially be running these on auto mode so not much control over things.

Title: Re: How to best 'right size' lights?
Post by: Taylor Hall on October 09, 2019, 07:28:22 am
With that kind of distance from the stage you could really use just about anything on the market unless you're trying to overpower the sun, which doesn't seem to be an issue given your use case. You'll probably end up running them below full blast anyways, we've found that all of our LED fixtures cause blinding issues unless we put them at about 70-80% intensity, and that's with a 20ft trim height. For reference, this is what 10 of the parts express BL-63 bar pars do from 80ft away at full tilt, and the most we measured from them with a kill-a-watt was 11W at the outlet. On top of that, they also use the older-style massive array of 100-200mW diodes instead of the newer 5-15W+ focused diodes you see. Going head to head, the new focused diode fixtures beat them out, but that's to be expected when they draw upwards of 40W.


If nothing else, it seems that watts seem to be an acceptable ballpark to compare LED fixtures, as long as the manufacturers rate their diodes correctly (which is a toss up when dealing with white label chinesium products). I'd look at whatever the biggest thing in your price range is and go from there. The worst thing that can happen is that you turn them down a bit and have more 'headroom' if needed.
Title: Re: How to best 'right size' lights?
Post by: Tim Weaver on October 09, 2019, 09:14:12 am
With that kind of distance from the stage you could really use just about anything on the market unless you're trying to overpower the sun, which doesn't seem to be an issue given your use case. You'll probably end up running them below full blast anyways, we've found that all of our LED fixtures cause blinding issues unless we put them at about 70-80% intensity, and that's with a 20ft trim height. For reference, this is what 10 of the parts express BL-63 bar pars do from 80ft away at full tilt, and the most we measured from them with a kill-a-watt was 11W at the outlet. On top of that, they also use the older-style massive array of 100-200mW diodes instead of the newer 5-15W+ focused diodes you see. Going head to head, the new focused diode fixtures beat them out, but that's to be expected when they draw upwards of 40W.


If nothing else, it seems that watts seem to be an acceptable ballpark to compare LED fixtures, as long as the manufacturers rate their diodes correctly (which is a toss up when dealing with white label chinesium products). I'd look at whatever the biggest thing in your price range is and go from there. The worst thing that can happen is that you turn them down a bit and have more 'headroom' if needed.


Instead of just comparing lights using the "xxx Watts per LED" (5x15W, etc) look at the power draw. If they are truly 5x15 Watt LED's, then they would draw 75 watts PLUS whatever the PSU takes which is usually another 10% or so. So a 5x15 watt LED can should be drawing 80 to 90 watts at full-on. You'll see many Chinesium brands that list the power draw as less than the total of "LED watts". Makes you wonder how they are acheiving free energy.....


If you can stick to the better, established Chinese brands. Chauvet, Elation, ADJ, Blizzard. Chauvet in particular is making great strides in cheap but good lights right now.

Resist the urge to buy the "75 lights plus dmx cable for 23 american kopeks" deals you see on ebay. Most of the time you can meet or beat the output of all those lights with just 2 good name brand fixtures.


Also, look on Guitar Center's used page. I've seen older Colorado's go for 30-40 bucks each before. That's a serious light. Sometimes "Pro" gear goes for real cheap on GC's used page because the DJ's don't recognize it.
Title: Re: How to best 'right size' lights?
Post by: Taylor Hall on October 09, 2019, 10:32:25 am

Instead of just comparing lights using the "xxx Watts per LED" (5x15W, etc) look at the power draw. If they are truly 5x15 Watt LED's, then they would draw 75 watts PLUS whatever the PSU takes which is usually another 10% or so. So a 5x15 watt LED can should be drawing 80 to 90 watts at full-on. You'll see many Chinesium brands that list the power draw as less than the total of "LED watts". Makes you wonder how they are acheiving free energy.....
Yes this, I should have clarified that in my post for the second paragraph, sometimes my brain makes assumptions that my fingers don't pick up on. Especially early in the morning...
Title: Re: How to best 'right size' lights?
Post by: Mark Cadwallader on October 09, 2019, 10:51:28 am
At the risk of sounding like a lampie, I have some questions:

1.  When you say "down stage wash", are you talking about (a) an overhead stage wash; (b) general front lighting from FOH; or (c) something else?

2.  Are you cross-lighting the area with two or more lights, or just overlapping the fields of straight-ahead FOH lights?

3. By "see the performers", do you mean general illumination to distinquish the guitar player from the vocalist, or enough to see facial expressions?

4. Are your front lights generally 45 degrees above the performers and to the sides of the performers?  In the 30 to 60 degree range above?
Title: Re: How to best 'right size' lights?
Post by: TJ (Tom) Cornish on October 09, 2019, 12:29:02 pm
OK, I realize this is a sound forum, but the Controlbooth guys do this too - after multiple replies, no one has mentioned arguably the most important metric - beam angle. Throw distance is a useless metric unless you specify the pool size. A low wattage narrow beam light will seem much brighter than a high wattage wide beam light at the same throw distance.

Many LED pars are around 20˚ beam angle. You can use one of the online throw calculators to help you decide if that translates to an appropriate pool size at the throw distance you need to work at.

Back to the wattage question - 100w LED fixtures in a relevant beam angle tend to be pretty useful. I wouldn’t own any much smaller than that. If you are only looking for a single light per side of the stage illuminating the whole darn thing, a high-wattage wide-beam angle light might be better (I’m not necessarily recommending this).
Title: Re: How to best 'right size' lights?
Post by: Dave Garoutte on October 09, 2019, 01:17:10 pm
OK, I realize this is a sound forum, but the Controlbooth guys do this too - after multiple replies, no one has mentioned arguably the most important metric - beam angle. Throw distance is a useless metric unless you specify the pool size. A low wattage narrow beam light will seem much brighter than a high wattage wide beam light at the same throw distance.

Many LED pars are around 20˚ beam angle. You can use one of the online throw calculators to help you decide if that translates to an appropriate pool size at the throw distance you need to work at.

Back to the wattage question - 100w LED fixtures in a relevant beam angle tend to be pretty useful. I wouldn’t own any much smaller than that. If you are only looking for a single light per side of the stage illuminating the whole darn thing, a high-wattage wide-beam angle light might be better (I’m not necessarily recommending this).

+1 Beam angle.
Light follows the inverse square law, for both distance and beam angle.
X lumens (output) at 20 degrees gives Y lux (received).
X lumens at 40 degrees gives Y/4 lux.

The apparent brightness of LEDs to the talent has a lot to do with the specularity (think of sunlight off a bumper) of the emitter. 
The early exposed element type were 'blinding' even though they weren't that bright in actual output.
The later versions with the lenses are much better in this respect. 
The best are the fresnel type COBs or the fixtures with collimated single output lenses.
The less specularity, the more output you can get without frying the eyes of your subject.
Title: Re: How to best 'right size' lights?
Post by: Mal Brown on October 09, 2019, 02:47:22 pm
I would adore a cost effective Ip65 in the 70 to 90 watt color mixing range.  Most of what I have seen has been either crazy expensive (compared to the potential for revenue generation in my locale).
Title: Re: How to best 'right size' lights?
Post by: Tim Hite on October 09, 2019, 03:58:48 pm
I would adore a cost effective Ip65 in the 70 to 90 watt color mixing range.  Most of what I have seen has been either crazy expensive (compared to the potential for revenue generation in my locale).

If I find something good I'll just ship it up to you for the summer so your rain can wash off my dust.
Title: Re: How to best 'right size' lights?
Post by: Tim Hite on October 09, 2019, 04:02:25 pm
At the risk of sounding like a lampie, I have some questions:

1.  When you say "down stage wash", are you talking about (a) an overhead stage wash; (b) general front lighting from FOH; or (c) something else?

2.  Are you cross-lighting the area with two or more lights, or just overlapping the fields of straight-ahead FOH lights?

3. By "see the performers", do you mean general illumination to distinquish the guitar player from the vocalist, or enough to see facial expressions?

4. Are your front lights generally 45 degrees above the performers and to the sides of the performers?  In the 30 to 60 degree range above?

1) all those scenarios, potentially.
2) Situationally dependent on client budget
3) that is the crux of my inquiry. How much light/lux etc do I need to put on performers to achieve various levels of illumination and visibility?
4) again situationally dependent.

I understand the inverse square law and know about beam angle and such, I have no idea how much light I need hitting the performers to achieve various results. As such, it's not possible for me to calculate anything meaningful, since I don't know the desired end state or "how much light do I need on the performers?".
Title: Re: How to best 'right size' lights?
Post by: Dave Garoutte on October 09, 2019, 04:54:49 pm
I have a Cen-Tech P98674  multi-meter  (https://www.harborfreight.com/5-in-1-digital-multimeter-98674.html) that has a lux meter and a dB meter on board.
It wasn't that expensive.
Different situations call for different amounts of light, so you could determine what's right for you.
Title: Re: How to best 'right size' lights?
Post by: Jeff Lelko on October 09, 2019, 08:06:59 pm
Hi Tim, if true outdoor wet location use is needed, I’d look towards either the Elation SixPar Series or Chauvet COLORdash Par H12IP.  Oftentimes the direct from China fixtures that claim to be IP65 don’t actually hold up properly in wet location uses.  Another thing to keep in mind is that even though you’ll be outside at night, the amount of ambient light you’ll have to content with isn’t zero.  Getting four of these types of fixtures on each tripod/totem would probably be about right as a point of departure.

As far as the whole “blinding” issue goes, in addition to what Dave said, getting your angles right really helps too.  If the fixtures are pointed too “head-on”, yes, your talent will complain.  Getting the lights up in the air and off to the side can work wonders in this regard.  Hope this helps!
Title: Re: How to best 'right size' lights?
Post by: Callan Browne on October 15, 2019, 07:56:58 am
1) all those scenarios, potentially.
2) Situationally dependent on client budget
3) that is the crux of my inquiry. How much light/lux etc do I need to put on performers to achieve various levels of illumination and visibility?
4) again situationally dependent.

I understand the inverse square law and know about beam angle and such, I have no idea how much light I need hitting the performers to achieve various results. As such, it's not possible for me to calculate anything meaningful, since I don't know the desired end state or "how much light do I need on the performers?".
Do you think you need more or less light than this:
(https://uploads.tapatalk-cdn.com/20190502/77fcba161d7f5373fb65c15e9067e41f.jpg)

My very basic setup, rgba hotbox * 4 out front and 8 Chauvet units at the back (half t12 half Pro q)
Title: Re: How to best 'right size' lights?
Post by: Tim Hite on October 15, 2019, 01:45:18 pm
Do you think you need more or less light than this:

My very basic setup, rgba hotbox * 4 out front and 8 Chauvet units at the back (half t12 half Pro q)

That's seems to be about where I'm headed. I just lit a small two piece act this weekend with a pair of 70w LEDs on the ground and it was quite a bit more light than what I was expecting for $50 Solana lights. Something like 10 of those on a 32x16 stage will hopefully be adequate.