LEDs & banding

[HolisticBear]

I haven't found many threads discussing the 'banding' I see in photographs under LEDs. I assume this is related to the disco effect of LEDs, multiple point lights at different wavelengths. I assume the bands are cases where the camera sensor simply fails to blend the lights? Is that's correct, a few questions

* Faster shutter speed would make it occur more often, yes? My images back this up.
* Are some LEDs better or worse than others? I'm using an AI Prime. Would the latest Radion be better, a Kessil even better than Radion, and finally T5 wouldn't have this issue at all?
* Can I adjust the lights to make it occur less? (mostly white or equal on all channels?)

An example no bands (1/100s) and one with bands (1/160s)

 

[jsker]

Good question, and I would say @saltyfilmfolks would be the best for answers.

 

[saltyfilmfolks]

Yup. You'll want to search photography threads and forums.
Leds Strobe. And they strobe at a set frequency.

 

[HolisticBear]

Yup. You'll want to search photography threads and forums.
Leds Strobe. And they strobe at a set frequency.

Thanks. Now I know the proper keywords

 

[saltyfilmfolks]

Cool. Fwiw actual photographic strobes do the same exact thing with a shutter speed set too high.
So you can look there too.

 

[NanaReefer]

Never seen this before. Have used 2 different LED units over the past 5yrs. Very strange.

 

[nc208082]

Cool. Fwiw actual photographic strobes do the same exact thing with a shutter speed set too high.
So you can look there too.

Could you explain this a bit more. I've never seen those bands when shooting anytging.

 

[saltyfilmfolks]

Never seen this before. Have used 2 different LED units over the past 5yrs. Very strange.

Yea. Curious.

What brand is the led and are you in the us?

 

[saltyfilmfolks]

Could you explain this a bit more. I've never seen those bands when shooting anytging.

Have you used strobes?

In short. The shutter time is too fast to expose the entire frame before the light turns off. In strobes it's set milliseconds. In arc lights (mh) the arc is not constant it's on and of at 120 times per second. Or 60 hertz.

 

[nc208082]

That makes sense thanks for the clarification. I've used strobe lights yes I just didn't realize LEDs light that way. I've photographed under leds but never seen those bands like that. To be honest I've only seen those bands show up when i take a picture of a tv or something like that.

 

[HolisticBear]

Never seen this before. Have used 2 different LED units over the past 5yrs. Very strange.

Given how brutal it is, I was surprised there weren't more mentions. It makes photography on my Android phone impossible and the photos above are from a micro 4/3rds sensor. I'm using the original AI Prime (budget led), so I wondered if it was mostly a side affect of that light. It mostly occurs at faster shutter speeds when I'm trying to get the fish in focus.

I'm replacing the lights next month (lean towards Mitras or AP700) and photography is a factor. I know MH/T5 are better, but I'm guessing newer LEDs are better than this prime.

 

[nc208082]

The ai prime uses cree and semileds. Those are both good high end leds so I don't think the brand of leds is making this happen.

 

[HolisticBear]

The ai prime uses cree and semileds. Those are both good high end leds so I don't think the brand of leds is making this happen.

I wonder if the dimmer has an effect? I'm not running the lights at 100%. Maybe it occurs more at 35% than 80+%? Will have to test

 

[saltyfilmfolks]

It has to do with the frequency of the light.
I suppose (not an led bulder) that the signal to the led is PWM and could be what's going on.

Hmmm.
@Brew12 you around?

 

[Brew12]

It has to do with the frequency of the light.
I suppose (not an led bulder) that the signal to the led is PWM and could be what's going on.

Hmmm.
@Brew12 you around?

Thanks for the invite!

Yup, LED's will flicker due to pulse width modulation. To vary the brightness of an LED you can vary the voltage, or use PWM to flicker the light on and off to make it effectively dimmer. You can get a much larger range of brightness using PWM.
Just to make sure there isn't confusion, it isn't the PWM that comes from the controller. For example, an Apex can send a 0-10V signal to a light fixture as a control signal. The LED controller can then use PWM to make the LED's brighter or dimmer.

 

[saltyfilmfolks]

Thanks for the invite!

Yup, LED's will flicker due to pulse width modulation. To vary the brightness of an LED you can vary the voltage, or use PWM to flicker the light on and off to make it effectively dimmer. You can get a much larger range of brightness using PWM.
Just to make sure there isn't confusion, it isn't the PWM that comes from the controller. For example, an Apex can send a 0-10V signal to a light fixture as a control signal. The LED controller can then use PWM to make the LED's brighter or dimmer.

Now they're a two ways to dim in fixtures I belive.
Why do you think his older led and ai would do this but not others?

 

[Brew12]

Now they're a two ways to dim in fixtures I belive.
Why do you think his older led and ai would do this but not others?

Without knowing more about the fixtures and how they are controlled I can only guess. I will throw out a few theories.

Controllers with fewer, higher voltage and higher quality LED's will be more likely to be controlled by varying voltage, not PWM.
The newer fixtures may have more controllable channels, so the LED's aren't all flickering at the same time.
It could be a coincidence that the older LED's circuitry flickered at the same rate as the processor in the camera (least likely)

 

[HolisticBear]

Now they're a two ways to dim in fixtures I belive.
Why do you think his older led and ai would do this but not others?

So I googled AI and PWM and came across and article on another forum. It was in reference to people complaining about buzzing. The snippet said the advantage of PWM over changing current is that the color doesn't shift (which happens with changing current).

In the AI app, you first pick a kelvin setting then pick and an intensity setting. Maybe it's by design so it can hold 14k (or whatever temperature) from 0 to 100% without color shifting?

 

[saltyfilmfolks]

Yea it probably is. But most led are that way as I recall.
It's possible is suppose maybe. It's just a glitch ?

I've only run across this in a few photo venues with led projectors and effects. Not heard of it in tank fixtures.

 

[Brew12]

So I googled AI and PWM and came across and article on another forum. It was in reference to people complaining about buzzing. The snippet said the advantage of PWM over changing current is that the color doesn't shift (which happens with changing current).

In the AI app, you first pick a kelvin setting then pick and an intensity setting. Maybe it's by design so it can hold 14k (or whatever temperature) from 0 to 100% without color shifting?

That is true. Using PWM to change brightness will not cause the color shift that changing voltage will.