led lighting flicker at DVinfo.net

Paul Mailath · June 5th, 2012, 01:48 AM

This is a new reception facility - they use some type of LED lighting and the camera picks up a pulsing effect
No they're not fleuro's - I checked

I adjusted to minimise (it never seemed to completely go but was minor but the pulsing speed seemed to change as the night wore on.

I might have to go back and do some tests - any idea how to minimise something like this in post?

Frank Glencairn · June 5th, 2012, 02:49 AM

Yeah, it's known as pulsed modulation LEDs and it's a major PITA.

Unfortunally there is not much, you can do, but turn the LEDs off.

here is a good read: ProVideo Coalition.com: Stunning Good Looks by Art Adams

Frank

Nigel Barker · June 5th, 2012, 05:22 AM

The other problem with these wretched LED lights we encounter is some pink ones that are used in discos & receptions. They are so wildly skewed to that pink colour that it's all but impossible to get the white balance correct even doing custom WB with an Expodisc or grey card as there is such a magenta spike that the camera sees everything as pink.

Jaron Tauch · June 6th, 2012, 02:34 PM

While this doesn't work with dslr's, EX1's and other "regular" video cameras have a function called ECS. This stands for electronically controlled shutter and you can turn it on to dial out the flicker from the LED light.

Paul R Johnson · June 7th, 2012, 03:00 AM

Yes you can - but you need to constantly change it when somebody dims or brightens the light. It's a pest. It's also very, very bad with cheaper designs when the LED lights are near the bottom of their brightness range, when the flicker can even be seen in your peripheral vision. The trouble is, as mentioned by Frank, that Pulse Width Modulation - and googling this will reveal the nastier bits, means that they don't actually dim at all, but are just 'on' for less time. Most mains powered LEDs will be in sync with the mains frequency, 50/60Hz - but some LED designs that can be run from DV power generate the PWM frequency internally - and each unit may actually be on a slightly different frequency - making flicker free results a bit random!

June 5th, 2012, 01:48 AM	#1
Paul Mailath Trustee Join Date: Dec 2006 Location: Central Coast - NSW, Australia Posts: 1,606	led lighting flicker This is a new reception facility - they use some type of LED lighting and the camera picks up a pulsing effect No they're not fleuro's - I checked flicker on Vimeo I adjusted to minimise (it never seemed to completely go but was minor but the pulsing speed seemed to change as the night wore on. I might have to go back and do some tests - any idea how to minimise something like this in post? __________________ Cheers - Paul M. www.perbenyik.com

June 5th, 2012, 02:49 AM	#2
Frank Glencairn Regular Crew Join Date: Jun 2011 Location: Germany Posts: 176	Re: led lighting flicker Yeah, it's known as pulsed modulation LEDs and it's a major PITA. Unfortunally there is not much, you can do, but turn the LEDs off. here is a good read: ProVideo Coalition.com: Stunning Good Looks by Art Adams Frank

June 5th, 2012, 05:22 AM	#3
Nigel Barker Inner Circle Join Date: Feb 2009 Location: Norwich, Norfolk, UK Posts: 3,531	Re: led lighting flicker The other problem with these wretched LED lights we encounter is some pink ones that are used in discos & receptions. They are so wildly skewed to that pink colour that it's all but impossible to get the white balance correct even doing custom WB with an Expodisc or grey card as there is such a magenta spike that the camera sees everything as pink.

June 6th, 2012, 02:34 PM	#4
Jaron Tauch Regular Crew Join Date: Sep 2008 Location: Chicago, IL Posts: 34	Re: led lighting flicker While this doesn't work with dslr's, EX1's and other "regular" video cameras have a function called ECS. This stands for electronically controlled shutter and you can turn it on to dial out the flicker from the LED light.

June 7th, 2012, 03:00 AM	#5
Paul R Johnson Inner Circle Join Date: Nov 2005 Location: Lowestoft - UK Posts: 4,045	Re: led lighting flicker Yes you can - but you need to constantly change it when somebody dims or brightens the light. It's a pest. It's also very, very bad with cheaper designs when the LED lights are near the bottom of their brightness range, when the flicker can even be seen in your peripheral vision. The trouble is, as mentioned by Frank, that Pulse Width Modulation - and googling this will reveal the nastier bits, means that they don't actually dim at all, but are just 'on' for less time. Most mains powered LEDs will be in sync with the mains frequency, 50/60Hz - but some LED designs that can be run from DV power generate the PWM frequency internally - and each unit may actually be on a slightly different frequency - making flicker free results a bit random!