LED Lights problem

[Gary Nattrass]

I recently did a conference with three stages all with LED PAR56 type blue lights lighting the backdrop. Out of 12 lights four of them were pulsing when viewed thru the cameras a sony S270 and Z7. All the set-ups were identical but the stage guys said the four pulsing lights were a different make.

Both cameras were set the same with a shutter speed of 100 changing the shutter speed didnt seem to alter the effect. I was shooting in DVcam mode 25fps pal.

Video clip of the four offending lights here:YouTube - 01_0009_2008-10-21_104142-desktop.m4v

Any ideas?

[Richard Andrewski]

You didn't mention it but I'm guessing these were just operated directly off your 220v mains voltage in the UK as a light bulb would be--perhaps in an E27 socket or something like that? The issue would be that you're seeing a 50hz flicker from the line voltage on your camera. That's why its best to use direct dc voltage input type LEDs. Not to say that all LED bulbs powered directly off mains will have such a problem but some MAY have a problem. Some may handle this internally with an efficient AC to DC conversion in which case it wouldn't be noticeable. If that's not the case here, then there is some other issue internally with those bulbs which causes the flicker.

[Gary Nattrass]

Thanks Richard and yes they were direct from the 220v mains. As I said only four out of 12 lights did this and it was sods law they were on the main centre stage where all the big cheese speeches were made. I made the AV guys aware of the problem so hopefully they will not use them when a video is being made again. Sadly there wasnt time to swop them over as I arrived well after the rig on the morning of the conference.

[Richard Andrewski]

Right, I see you said 4 out of 12 now--didn't see that before. That definitely indicates those bulbs are just defective on their own internal power supplies then and should be changed out (or perhaps swapped to the periphery of the stage where the effect won't be so dramatic?).

[Bill Davis]

Originally Posted by Richard Andrewski

Right, I see you said 4 out of 12 now--didn't see that before. That definitely indicates those bulbs are just defective on their own internal power supplies then and should be changed out (or perhaps swapped to the periphery of the stage where the effect won't be so dramatic?).

Figure out who made them - cuz now you're going to have all the nightclub video guys screaming for them!

Imagine a whole room full of lights that don't make the club patrons sick - but look that WEIRD on the video. Tres COOL!

Effect looks kinda like a cheap sci-fi photon rocket drive or something!

Sign me up!