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TOPIC: Any hints on removing banding from LED lights?

Re: Any hints on removing banding from LED lights? 1 month, 3 weeks ago #223179

  • schrauber
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jwrl wrote:
[..] usually because this problem is due to an exposure variation a simple gain adjustment isn't enough. You may also need to adjust the gamma somewhat. It should be possible to link the two adjustments to the one setting.

Thanks.
I remember that users hugly and I did some experiments with different curves for easy brightness correction. But in the thread a lot of different effects were discussed.
After a long search I found the first effect code "negative-multiply".

To increase the setting range we experimented with "fn_gammaTest", which however has two setting parameters.

hugly experimented with this, and defined a default value for one parameter, so that a safe brightness correction (without running into saturation) became possible with only one parameter: "gammaV2"

Do you have solutions that are better suited to compensate for this banding?
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Software: Lightworks 2020.1; || Windows 10, 64 Bit
Hardware: Intel i5-4440 (3,1 GHz); || shared RAM: 8 GB; || Intel HD Graphics 4600 (can use max. 2 GB of shared RAM)

Re: Any hints on removing banding from LED lights? 1 month, 3 weeks ago #223185

  • schrauber
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schrauber wrote:
.. If more complex corrections are needed, this mask could be used to control other effects.

For example, the brightness / color correction for the lines could be adjusted even more precisely:

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In order for the spaces between the lines to require a special correction:
:pinch: Warning: Spoiler!
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Software: Lightworks 2020.1; || Windows 10, 64 Bit
Hardware: Intel i5-4440 (3,1 GHz); || shared RAM: 8 GB; || Intel HD Graphics 4600 (can use max. 2 GB of shared RAM)
Last Edit: 1 month, 3 weeks ago by schrauber.

Re: Any hints on removing banding from LED lights? 1 month, 3 weeks ago #223187

  • schrauber
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JimDaddyO wrote:
.. I downloaded it and extracted it to my effects templates folder in Lightworks. Is that the correct procedure?

The effect is installed in the same way as other user effects. General installation instructions: www.lwks.com/index.php?option=com_kunena&func=view&catid=7&id=188603&Itemid=81#188982

If you see the effect listed in Lightworks (category "Colour", subcategory "Repair tools") then the installation has worked.

JimDaddyO wrote:
.. I will give it a shot next edit..

Okay.
If you manage to avoid banding already on the recording, then you have a better solution.
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Software: Lightworks 2020.1; || Windows 10, 64 Bit
Hardware: Intel i5-4440 (3,1 GHz); || shared RAM: 8 GB; || Intel HD Graphics 4600 (can use max. 2 GB of shared RAM)

Re: Any hints on removing banding from LED lights? 1 month, 3 weeks ago #223189

  • hugly
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Resolve has a flicker filter with all sorts of bells and whistles to set up and tune.

After spending some times testing this thing on the video I've posted above and, if I was the DOP, lighting assistant and editor in one person, I would try everything I can to avoid this hassle in post and to get rid of the problem when shooting.

If frame rate settings don't fix the problem in the first place, I would replace the LED lights in the second.

My 2 cents.
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Re: Any hints on removing banding from LED lights? 1 month, 3 weeks ago #223192

  • David Rasberry
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Change the lights. It might take testing a few different fixtures, but fluorescent fixtures with high frequency ballasts and LEDs with good DC filtering don’t flicker.
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Re: Any hints on removing banding from LED lights? 1 month, 3 weeks ago #223198

  • jwrl
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A little bit of fundamental electrical theory: You can absolutely guarantee that the voltage feeding the LED is rectified. If it isn't, the flicker situation would be much worse, because the negative half of the AC cycle would not produce any light output at all.

Second, LEDs produce more output when they are pulsed, so that you can almost guarantee that there would be very little filtration of the rectified AC. You are probably getting almost a pure rectified AC input to the LEDS in the lamp.

Third, the phosphor will fluoresce almost as soon as it is energised, so it will track the leading edge of the rectified AC very closely. However it will continue to output light for some time after it is no longer energised, so that it will not track the trailing edge anywhere near as precisely. The diagram below will give an idea of what may actually be happening.

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The amount of phosphor lag will vary with the lights used, and will reduce as you dim the light, making the flicker worse. The illustration above has exaggerated how far the trailing lag drops for clarity. It won't get as low as that, but it will drop. However based on that, a rectified sine wave is perhaps the best approximation for any post production solution. But I agree completely with David. If you can manage it at all, get yourself appropriate lighting for your shoot.

(And if you think that preparing that diagram wasn't an absolute pain even simplified as it is...)
Last Edit: 1 month, 3 weeks ago by jwrl.

Re: Any hints on removing banding from LED lights? 1 month, 3 weeks ago #223199

  • JimDaddyO
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OK everyone....Thanks for all the input.

I got the effect installed and with minimum fussing it looks better. As the video is already released, I didn't save it and republish.

As for trying to fix it as I video? Yes, I think that is the best thing to do. I have made some adjustments to my camera. Turned off the AWB and set it to 5500K, I also slowed the shutter speed to 1/30 and saved those in the camera. (for reference, I am using a Lumix FZ 150 bridge camera...budgetary reasons, this is a hobby, not a career. Otherwise I would be looking at the new Sony A7s lll)

I think the shutter speed will be the best solution as each frame will now have 2x the exposure time than at 1/60. This will allow the light to go through it's whole cycle of dimming and brightening and hopefully even it out. A test is yet to be made, but that's the theory I am going on.

I do have a copy of Resolve on my computer and have only a brief play time with it to experiment. It's a big learning curve, I guess I have become more intuitive with the Lightworks method in my process, but I will soldier on with learning. So far I am still trying to figure out how to get just the section of the clip I've imported on to the time line. That's pretty basic. I guess "Mark and Park" has spoiled me...lol.

Much thanks to everyone in the thread who has chimed in. I tend to learn one little bit at a time and apply that to the next edit (still working on some colour correction at this point). It's all my little brain can handle at a time...lol.
Last Edit: 1 month, 3 weeks ago by JimDaddyO.

Re: Any hints on removing banding from LED lights? 1 month, 3 weeks ago #223200

  • hugly
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The question is, will your camera be able to record at 29.97 fps when setting the exposure time to 1/30th of a second, which depends on the kind of shutter it has.
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Re: Any hints on removing banding from LED lights? 1 month, 3 weeks ago #223201

  • briandrys
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I would only use 1/30th of a second when you're shooting with LED lights, don't use it all the time.

This is an issue that's been around for decades:

www.provideocoalition.com/rolling-shutter-and-flickering-hmis/

It says:

In “normal” mode (not “relative” mode) the RED ONE’s shutter is always absolute. In other cameras with rolling shutters, such as the Sony EX1/EX3, it’s relatively safe to assume that if the shutter speed is expressed as a fraction then the shutter speed is absolute.
Last Edit: 1 month, 3 weeks ago by briandrys.

Re: Any hints on removing banding from LED lights? 1 month, 3 weeks ago #223202

  • JimDaddyO
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hugly wrote:
The question is, will your camera be able to record at 29.97 fps when setting the exposure time to 1/30th of a second, which depends on the kind of shutter it has.


Yes.

Lighting improvements are on my list. We have our place up for sale, so it won't be until after we move and get settled in. I am hoping for some soft boxes of some sort, depending on what the new shop/studio will be. Which is also an answer to the next post in line about not using 1/30 shutter all the time.

I needed the correction for video I already have. Hopefully in the future this will not be an issue. I "upgraded" the lights in my present shop from flourescent to the cheapest LED units I could find on Amazon. They transfer noise to the radio too. Budget friendly is not always video friendly.

Re: Any hints on removing banding from LED lights? 1 month, 1 week ago #223791

  • JimDaddyO
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Just a bit of an update.

Falls under the "It figures" category....

Edited a video yesterday and none of the footage had the banding from the LED lights on it...lol.

Thanks for all the input folks. Much appreiciated by an amatuer like me.
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