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Author Topic: How to best 'right size' lights?  (Read 1146 times)

Tim Hite

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How to best 'right size' lights?
« 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.

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Taylor Hall

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Re: How to best 'right size' lights?
« Reply #1 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.
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Tim Weaver

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Re: How to best 'right size' lights?
« Reply #2 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.
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Taylor Hall

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Re: How to best 'right size' lights?
« Reply #3 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...
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Mark Cadwallader

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Re: How to best 'right size' lights?
« Reply #4 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?
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TJ (Tom) Cornish

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Re: How to best 'right size' lights?
« Reply #5 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).
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Dave Garoutte

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Re: How to best 'right size' lights?
« Reply #6 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.
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Mal Brown

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Re: How to best 'right size' lights?
« Reply #7 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).
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Tim Hite

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Re: How to best 'right size' lights?
« Reply #8 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.
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Tim Hite

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Re: How to best 'right size' lights?
« Reply #9 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?".
« Last Edit: October 09, 2019, 04:06:07 pm by Tim Hite »
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Re: How to best 'right size' lights?
« Reply #9 on: October 09, 2019, 04:02:25 pm »


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