How to avoid the "strobing" looking from LED accent lights in my shot

L

Lkorver

Well-known member
I just got back from a location scout. Shooting a product video for LED accent lighting. Its the type of LEDs that you string around behind picture frames, hand railing, etc. They change color and offer a nice glow around objects. However, I'm getting a terrible strobing look on camera that can somewhat be minimized shooting at 1/30th shutter but i'd love to avoid doing that. The only fix I found was to shoot at 28fps in 30p mode (hpx170). Not sure if I can even deliver a project in those settings?

I tried adjusting the shutter and syncro scan but couldn't find anything that worked. Anyone have any other ideas? thanks so much?

Luke
 
Hi Lkorver,

That can be a tough one. Did you try shooting at 1/60th? Most fluorescent/LED lighting in north america has a 60hz cycle based on the electrical code. Higher quality flouros and LEDs use a much higher refresh rate and do not flicker. If you can't find anything that will work, you could always shoot 28fps in 30p and edit it to a 30p, 24p or 60p/i timeline? The footage may speed up or slow down a little depending on the sequence settings, but might not matter depending on the content.


Jason

Hurrah - 1,000th post
 
Yep, this is absolutely an issue and it will continue to grow into a more and more problematic issue, as more dimming LEDs come on the market and as cameras have shifted to rolling-shutter CMOS instead of global-shutter CCD.

I bought a few LED lights to make a tiny portable lighting kit, I got a variety of them, and I found that one can be used when dimmed, but another absolutely cannot without causing the horrible scrolling bands. Here's a sample video I shot of the YongNuo YN160 light, at various dim settings:


Note, this only happens on a CMOS camera, the scrolling bands don't happen on CCD cameras.

It's definitely a problem.
 
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Yeah, here is the video I got, from the other post. Barry, do you have an suggestions to ameliorate the problem... like shutter speed variations? I am not sure if the frequency of the LED PWM circuits are even standardized.



 
David G. Smith said:
Yeah, here is the video I got, from the other post. Barry, do you have an suggestions to ameliorate the problem... like shutter speed variations? I am not sure if the frequency of the LED PWM circuits are even standardized.
Click to expand...
I chased all around with shutter speeds on the YN160, and I could occasionally find matches (i.e., 1/400th would work for one dim setting, but not another) and came to the conclusion that -- there is no solution. CMOS + dimming LCD = potential bands. Only two ways around it that I can find:
1) always turn the LCD up to 100% brightness, or
2) Ditch the CMOS and go with CCD.

Some lights are better than others, obviously. My Z96 and CN126 don't show banding at any dim level when on 1/60th, my YN160 shows banding on every dim level at nearly every shutter speed. I would have no way to even guess at what's gonna happen with stage lighting.

You could try using the absolute blurriest slowest shutter speed you can imagine, I guess, but ... the only real solution that I would be comfortable with would be to do a trial shoot beforehand to see if there's gonna be a problem and, if there is, rent a CCD camera for that venue for that day.
 
Barry_Green said:
I chased all around with shutter speeds on the YN160, and I could occasionally find matches (i.e., 1/400th would work for one dim setting, but not another) and came to the conclusion that -- there is no solution. CMOS + dimming LCD = potential bands. Only two ways around it that I can find:
1) always turn the LCD up to 100% brightness, or
2) Ditch the CMOS and go with CCD.

Some lights are better than others, obviously. My Z96 and CN126 don't show banding at any dim level when on 1/60th, my YN160 shows banding on every dim level at nearly every shutter speed. I would have no way to even guess at what's gonna happen with stage lighting.

You could try using the absolute blurriest slowest shutter speed you can imagine, I guess, but ... the only real solution that I would be comfortable with would be to do a trial shoot beforehand to see if there's gonna be a problem and, if there is, rent a CCD camera for that venue for that day.
Click to expand...

I was afraid you were going to say that!! Thanks. I have a feeling that this is going to become a bigger and bigger issue. Thanks again.
 
El Cheapo lights use what is known as PWM or Pulse Width Modulation to control the dimming. It basically pulses (turns the leds on and off at a fast rate) to control the perceived brightness. The faster they pulse the brighter it looks. It really is the driver in them that does this and not the leds themselves. If they only used quality constant current drivers in them ( really costs a few bucks more ) then there would be no flicker. It's all about the profits.
 
Argghhhh..luckily I still have my Sony HDR-FX1 for this. By the way, on a different note, do you guys have a strobe light pattern (from the actual LED's barn-door reflection itself) even when you are not recording. I will try to post this issue with a picture once I am back home. I believe the barn-door used is giving the inconsistent light reflection for some weird reason.
 
So to be clear, it's only a problem when you dim the lights? Why is that a problem then? Just use barn doors or move the light back or add more diffusion.
 
kicap said:
Argghhhh..luckily I still have my Sony HDR-FX1 for this. By the way, on a different note, do you guys have a strobe light pattern (from the actual LED's barn-door reflection itself) even when you are not recording. I will try to post this issue with a picture once I am back home. I believe the barn-door used is giving the inconsistent light reflection for some weird reason.
Click to expand...

If you are referring to 'fringes' at the edge where the barn door cuts off the light, without any other information, I'd say it would perhaps be due to the fact that an 'LED' light, as implemented by the ones I've seen mentioned here,
consists of a number of actual LEDs, and as such the barn door edge will yield different 'angles of view' for the array of LEDs, and so produce 'fringing' based on the placement of the LED in the array.

This is different from point source fringing... where that occurs due to the wave like nature of light...
 
Barry_Green said:
Yep, this is absolutely an issue and it will continue to grow into a more and more problematic issue, as more dimming LEDs come on the market and as cameras have shifted to rolling-shutter CMOS instead of global-shutter CCD.

I bought a few LED lights to make a tiny portable lighting kit, I got a variety of them, and I found that one can be used when dimmed, but another absolutely cannot without causing the horrible scrolling bands.
It's definitely a problem.
Click to expand...

Which one works the best ?
 
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