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[Mike Karseboom]

I have been trying to figure this out for a couple of years.   I have a variety of LED par type fixtures and sometimes want to strobe them.  Most have an internal strobe channel.  But most also loose a lot of intensity when strobing - like maybe 75%.  So instead of building the "energy" the strobing looks sort of lame.  Even at fairly slow rates, say 3/sec, it is dim.


I have tried using features in the control program to synthetically create the strobe.   For example  in Martin M-PC I create an effect on intensity with a variable swing rate using a square wave.  Experimenting with extending the limits of the swing all the way to 250% of max does help some.  I suppose it gives the fixture time to "catch up" and reach full off and full on.  But still, it is weak.


I guess I can understand this but then there are some internal functions on some of the same fixtures that seem to do very sharp color or intensity changes without loosing a bunch of intensity.


So I am wondering if this is typical  - that LED fixtures loose a LOT of intensity when strobing.  Or is there something else I can try to get sharp, high intensity strobes.

[Jeff Lelko]

So I am wondering if this is typical  - that LED fixtures loose a LOT of intensity when strobing.  Or is there something else I can try to get sharp, high intensity strobes.

None of the fixtures I own or have used do this.  One of the benefits of LED lighting is that the fixture's response time should be nearly instantaneous and that you don't have to swing pieces of metal in front of a lamp to control the output. 

Which fixtures are you using?  Do they have dimmer curve settings?

[Mike Karseboom]

Ha - the low cost moving head lights with mechanical shutter are the only ones that don't loose any apparent brightness on strobing!


The LED fixtures I use the most are Chauvet SlimPar Pro Tri  and Becen BC-P504 12x15 RGBWA pars.  The Chauvet have a dimming curve setting with 5x options:  default dimmer speed, linear dimmer, non-linear dimmer 1, 2, and 3.  I think I set it to  linear because the fade to zero was a little smoother.  Perhaps that is affecting the strobe.


The Becen does not have a dimmer curve option.


On the stages I typically work the lights are too bright at full power and so are often at less than 50% on the "dimmer" channel.  Could that be affecting the strobe?  the loss of intensity on strobing seems to be proportional to the dimmer channel setting but always appears to be be quite a bit less bright than whatever the steady state is.   Also this is for any color including white created from color mixing.

[TJ (Tom) Cornish]

I wonder if the issue isn't brightness as much as dwell time.  If the flash duration is too short, it may indeed be full brightness, but not for long enough to appear as bright based on how we perceive light.  Your lights with mechanical shutters appear full brightness because the shutter is slower - it's open longer.

Not sure that's actionable information as it's likely the built-in strobe function of the fixtures is probably not adjustable, but I would bet this is the issue.

[Mark Cadwallader]

I think TJ is right. With a conventional strobe, there is a warm up and cool off period besides the period of full discharge. That ramp up/full/ramp down cycle has a longer emission period than the "instant on/instant off" discharge from an LED.

[Mike Karseboom]

Thanks for the input so far.  It probably is dwell time.  The internal strobes do have adjustable rates.   And, of course, my software created strobe effect is adjustable.  It sure seems like even slow strobes are dim.  But it is probably me that is dim.


As usual no time to really investigate at the gig so I plan to play with this more at home and will  report back.

[Nathan Riddle]

The Manual says there are 4 dimmer curves. I'd set it to off. [I may have the wrong manual]

Most of the time the dimmer curves are so the light functions more like a standard halogen light fixture. That means slow on/off. I wouldn't imagine it would affect the strobe, but it could?

[Mark Cadwallader]

A dimmer curve for incandescent lights is hard-pressed to replicate the triggering of a true strobe tube. Blinders, when used for a strobe effect, have a similar "flash", but they are usually way, way brighter than the wash or "specials" lighting.

[Mike Karseboom]

Just wanted to report back after experimenting more with my dim strobe problem.  It pretty much was a combination of trying to strobe to fast and also having the lights at low power.


The "too fast" strobing resulted in low dwell time for the "on" cycle and the resulting perception of dimness.  It turns out a slower strobe rate still works pretty well to get the effect and the increase in perceived brightness outweighs the super fast speed.


The fixtures are operating at a low intensity level due to small stage size and this also seems to have a big impact on how bright they look when strobing.  The way I have the intensity set up on an inhibitive fader (Martin MPC), makes it tough to allow the fixture to go to full intensity just for the strobe. I need to research how I might override the inhibitive fader temporarily during a strobe cue.


So the fixtures do seem provide a reasonably bright strobe effect whether using the internal strobe dmx channel or synthetically creating a strobe effect with the control software as long as you don't go super fast (>5 /sec ?).   The internal dimmer curve setting did not seem to make much difference but having the lights at a low intensity really lessens the impact.