Simple guide to LEDs?

[karl]

I've been intrigued by LED fixtures for a while but find the whole subject rather confusing. It seems that every man and his dog are producing/selling LED fixtures these days ranging from parcans for <£50 to units for >£1000.

 

Trouble is getting reliable figures for performance seems impossible, not help by the more ludicrous claims made by some manufacturers. So I was wondering how units compare.

 

Do expensive units actually produce much greater outputs or is build and design quality what you're paying for?

 

Are hundreds of 10mm UltraBright LEDs equivalent to a few 1W or 3W LEDs?

 

Are any of the lower end products (<£150) actually any use for lighting small theatre stages or are they all DJ toys?

 

The more I've researched and read the more confused I get!

[Ellis]

LED fixtures vary most at the lower end of the dimming range. Current dimming serves to cover much of the diming curve, but eventually they reach the point where there is insufficient potential difference for any current to flow, and hence they switch off.

 

More expensive units switsh to another dimming technique such as pulse-width dimming to smoth the lower end.

 

Paying more, you get better engineering - i.e. more robust and better heat management.

 

Used carefully, even the cheapest units have their place in theatre. Remember that where you might put four PARS in different colours, you can put four LEDs at much lower power and have many more possible colours. So 4 units with a lower individual luminous intensity can give a halogen PAR rig with a similar number of units a run for its money.

[nplatt]

Over the past 2 years our theater group has bought about 40 Eurolite for Thomann for about £65 each. We use then in our village hall panto maily to create an atmospheres things like dark caves or when the kids do a disco type song. we still have some traditional lights (if that’s the right word) as the output on these is not enough to fully light the stage but to create a atmosphere they work well for us.

[musht]

LED fixtures vary most at the lower end of the dimming range. Current dimming serves to cover much of the diming curve, but eventually they reach the point where there is insufficient potential difference for any current to flow, and hence they switch off.

 

 

Very good point about dimming curve, but its not something spending more guarantees getting any better, some very expensive lights don`t do the 0-25% bit well.

 

BTW actually have it in reverse most use some variant of PWM , current dimming has side effect of slightly, as in very slightly, changing colour which is used for colour matching in some systems,a green LED will visibly light from a few millionths of an amp.

 

Performance numbers are played with by everyone including the makers of the raw components, knowing the difference between Lumens and Lux will put you ahead of most of the people trying to sell you the things.

 

More money you pay gets nicer build quality, probably better dimming, probably named brand LEDs, it wont neccesarily buy you brighter units.

 

Its easier to heat sink big LEDs, 10mm is really a bit of a bodge, yes 1 & 3W LEDs are generally a better idea.

 

More money won`t buy you different colours, all LEDs rely on same chemistry, so RGB is RGB from a 30 quid Stairville or grands worth of Pixelrange.

 

LEDs do colours well, they still don`t do a tungsten competitive white well , yet....

 

Even with an unlimited budget you couldn`t change your whole rig over to LED succesfully.

 

Some great value LED gear available if you realise its limitations and exploit its advantages.

[karl]

We use then in our village hall panto maily to create an atmospheres things like dark caves or when the kids do a disco type song. we still have some traditional lights (if that’s the right word) as the output on these is not enough to fully light the stage but to create a atmosphere they work well for us.

That's pretty much the sort of thing I was thinking of. I know a couple of small (village hall size) venues that have enough lights/dimmer channels for a general wash and a few specials but not enough for pantos, dance shows, etc that need lots of colours.

 

Very good point about dimming curve, but its not something spending more guarantees getting any better, some very expensive lights don`t do the 0-25% bit well.

That's interesting. Is that some sort of inherent limitation with LED fixtures?

 

More money you pay gets nicer build quality, probably better dimming, probably named brand LEDs, it wont neccesarily buy you brighter units.

Again that's interesting. Lots of sources tell us that LED's don't match conventional fixtures for output (yet) but there seems to be little reliable info available about relative outputs for LED units. I've only ever seen a handful of LED fixtures and not in a way that allowed side by side comparison.

 

LEDs do colours well, they still don`t do a tungsten competitive white well , yet....

 

Even with an unlimited budget you couldn`t change your whole rig over to LED succesfully.

As I say it's more a case of being able to do a variety of colours easily.

 

Thanks for the info, it gives me something to contemplate.