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Tungsten to LED rough equivalents


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Hi guys, new to the forum, not to the industry, however I have been out for a while and im not up to date on LED fixtures.


I have inherited a partly tungsten rig that is awful to access and the few foh profiles (cantatas) are prime candidate for a swap to LED, unfortunately I have no idea what wattage will be needed to perform the job of a 1.2k lantern, preferably a little brighter, on par with maybe a clean tungsten source4? 

I am aware of ETC's selection but the budget is inevitibly going to have me looking at a lesser product.  Same question for 1k fresnels if possible.



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If it's just raw brightness you're interested in, you can actually look up the photometrics.  A Cantata 18/32, when new, provided 1190 Lux.  (Source)  An ETC Colorsource V with a 15-30 zoom lens provides between 1518 and 484 lux, depending on zoom.  (Source).  

The Cantata doesn't say what zoom level it was measured at so I would assume that figure is for it at it's narrowest.  They seem broadly comparable, and I would assume your Cantatas are not performing at their prime any more anyway.   Colorsource V is about 200W, so you're probably looking for fixtures in the 150-200W range.

BUT:  Additive colour mixing, in saturated colours, is going to be much brighter than the subtractive colour (gel) for the Cantatas, so depending on how you're using them, you may be able to err lower.

Having looked at the options, I've found that ETC's stuff is actually pretty price competitive at this level of product.    There are cheaper fixtures but they're way worse, and there are worthy competitors, but they are almost the same price IME.   Matching a 1.2K is actually pretty hard work, so you need something fairly good.  The Prolights stuff is reasonable and might be worth looking at:  https://www.prolights.it/product/ECLFS.  They don't seem to have Photometrics for their Zoom lenses, but their figures for fixed lenses are very respectable. (But, obviously, that's to be expected - you'll get better performance from a fixed lens.). The Chauvet E2FC is also in the ballpark and a nice fixture, but not as cheap as you might hope.  


And caveat:  Manufacturers can be pretty naughty when measuring and declaring their photometrics, especially at the low end.  Do get a real-world demo before pulling the trigger...

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Thanks for the info Bryson, sounds like if I can score some 200w fixtures ill have plenty of punch, they will largely be used as open white front of stage cover for basically everything, the cantatas are completely underwhelming compared to the LEDJ washes they have in the boom positions. Thanks for your input.

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Find a couple of options within budget and then get some for a demo. Shoot them out, both between the replacement options and with your existing cantatas. Possibly even invite the money people along to see the difference for themselves. 

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Don't compare LED fixture wattage.
It doesn't tell you anything much about brightness, unfortunately.

LED technology has changed very fast, and the quality & efficiency of the optics varies considerably between products.

This means that the final "lumens per Watt" (lm/W) of LED fixtures varies wildly.
At home I've got some 5W LED lamps that are considerably brighter than the 8W lamps I bought a couple of years before, despite being the same manufacturer and colour temperature.

There's LED spots on the market that have fewer lumens per Watt than an HPL Source Four - at 200W they'd be the dimmest thing in your venue.

The published figures to look at are the lux (or lumens) in the beam.

However, as Bryson mentioned, take brightness figures with a liberal helping of salt.

  • The measured brightness of a colour mixing or variable-white fixture varies greatly depending on the chosen colour.
    Many manufacturers only publish brightness at the single brightest shade of "white" - and that's often not a colour you'll ever want to use. (It's often a yucky pink or green)
  • An additive colour mixing LED that's dimmer in 3200K white is often brighter in saturated or even pale tints than the nearest-equivalent gelled tungsten.

For theatrical usage I'd strongly recommend additive colour mixing LED (RGBL or better), even if you think you'll nearly always want them in "open white".

  • Single-colour white LED will never really match each other (or anything else in the rig).
    The cheaper ones use rather wide 'binning' so are often very different colours, even within the same nominal batch.
  • The "white" is usually a very high colour temp (blue-white) as that measures brighter, but you'll likely actually want something warmer like your Cantatas.
  • Gel is getting harder to buy with longer lead times, and doesn't behave like you'd expect in front of LED.
    (Lee make an LED series that tries to make LED match tungsten, if you go that route)

Uncalibrated colour mixing fixtures also have some 'binning' colour consistency limitations, but it's generally a smaller difference - and of course you can manually match them as needed.

Calibrated colour mixing fixtures like the ETC ColorSource Spot V avoid that issue as they're matched in the factory.

Check the lux/lumens for 'supposedly' comparable fixtures, and get real demos.

Light some people, costume and painted set/cloths.
Run them for quite a while, you want to see what happens once they get warm - do fans get loud or distracting, does brightness drop?

Any dealer worth their salt will happily demonstrate their offerings.

Edited by Tomo
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To add to the points already made, note that incandescent lamps are very sensitive to variations in supply voltage. At 220 volts they will be significantly dimmer than at 250 volts, and both these voltages are within the expected and permitted range. I have seen as low as 200 volts at the lantern, that will give a decidedly inferior light with incandescent.

LED lanterns by contrast use a regulated power supply and will give constant light at any reasonable voltage.

LEDs will therefore seem much better in comparison with incandescent in a venue with a low supply voltage than in one with a generous voltage.

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