LED Light Panel Flickering?

[GeekaWhat]

I started a new topic yesterday with softboxes vs led panels for video and something came up about getting certain LED panels because others will 'flicker' when you record videos. Any help with this please?

 

Thanks

[Enderman]

That's because wall power is 60Hz and cameras usually record at 30 or 60fps which is the same

[Glenwing]

That's because wall power is 60Hz and cameras usually record at 30 or 60fps which is the same

It's got nothing to do with wall power. The 60Hz AC from the wall goes through several conversions to DC in the power supply before it ever reaches electronic components.

I started a new topic yesterday with softboxes vs led panels for video and something came up about getting certain LED panels because others will 'flicker' when you record videos. Any help with this please?

Thanks

This has to do with the method of brightness control being used. Some monitors (particularly budget ones, but some higher end ones as well) use something called "PWM" which is high-speed flickering. To display lower brightness it lowers the duty cycle, which is to say it turns "on" for less time during each flicker, so the total light output is less. Most monitors have a PWM frequency fast enough to be unnoticeable by the human eye, but cameras will pick it up easily at standard framerates.

You need a monitor with an actual dimming circuit, known as DC brightness control (direct current) which changes the voltages to make the light shine at a dimmer brightness. Most of the recent models from Dell and BenQ have flicker-free backlights, but you can reference tftcentral's flicker-free database to confirm.

[Bsmith]

It's got nothing to do with wall power. The 60Hz AC from the wall goes through several conversions to DC in the power supply before it ever reaches electronic components.

This has to do with the method of brightness control being used. Some monitors (particularly budget ones, but some higher end ones as well) use something called "PWM" which is high-speed flickering. To display lower brightness it lowers the duty cycle, which is to say it turns "on" for less time during each flicker, so the total light output is less. Most monitors have a PWM frequency fast enough to be unnoticeable by the human eye, but cameras will pick it up easily at standard framerates.

You need a monitor with an actual dimming circuit, known as DC brightness control (direct current) which changes the voltages to make the light shine at a dimmer brightness. Most of the recent models from Dell and BenQ have flicker-free backlights, but you can reference tftcentral's flicker-free database to confirm.

(ohh my a chance to correct a moderator!)

 

ehmm he is talking about LED light panels, not monitors, so it actually has to do with wallpower.

 

like @Enderman said, the flickering might occur when the shutterspeed and flickerspeed sync up, have the same speed or a number which can be divided form it( if 60Hz then use numbers as, 30fps and maybe 45fps)

[Glenwing]

(ohh my a chance to correct a moderator!)

 

ehmm he is talking about LED light panels, not monitors, so it actually has to do with wallpower.

 

like @Enderman said, the flickering might occur when the shutterspeed and flickerspeed sync up, have the same speed or a number which can be divided form it( if 60Hz then use numbers as, 30fps and maybe 45fps)

 

Oh I see I stand corrected then.

[.spider.]

flicker-free backlights,

But they still could have scanning backlight?

[Glenwing]

But they still could have scanning backlight?

 

What do you mean?

[.spider.]

What do you mean?

The LED Backlight is turned on/off at typically 3x fps so each frame is showed 3 times like they do in cinema.

This should be independent from the backlight brightness control.

[Glenwing]

The LED Backlight is turned on/off at typically 3x fps so each frame is showed 3 times like they do in cinema.

This should be independent from the backlight brightness control.

 

Oh, sure. The brightness is determined by the duty cycle (on-time to off-time ratio during each pulse) not the number of pulses per second or per frame (frequency).

[GeekaWhat]

Oh, sure. The brightness is determined by the duty cycle (on-time to off-time ratio during each pulse) not the number of pulses per second or per frame (frequency).

So how can I make sure, when recording at 1080p 30FPS with these light panels: http://www.amazon.co.uk/Neewer-Photography-Lighting-including-Camcorder/dp/B00LVTZH9I/ref=sr_1_3?ie=UTF8&qid=1426886125&sr=8-3&keywords=video+lights   that I get no flicker - (that will really ruin any professionalism! )

[GeekaWhat]

(ohh my a chance to correct a moderator!)

 

ehmm he is talking about LED light panels, not monitors, so it actually has to do with wallpower.

 

like @Enderman said, the flickering might occur when the shutterspeed and flickerspeed sync up, have the same speed or a number which can be divided form it( if 60Hz then use numbers as, 30fps and maybe 45fps)

 

So how can I make sure, when recording at 1080p 30FPS with these light panels: http://www.amazon.co...ds=video lights   that I get no flicker - (that will really ruin any professionalism!  )

[Kermit]

Unless it's the same frequency, they will always flicker on camera

[GeekaWhat]

Unless it's the same frequency, they will always flicker on camera

 

How will I know if these light panels: http://www.amazon.co.uk/Neewer-Photography-Lighting-including-Camcorder/dp/B00LVTZH9I/ref=sr_1_3?ie=UTF8&qid=1426886125&sr=8-3&keywords=video+lights        are the same frequency as the 1200d at 1080p at 30FPS 

[Kermit]

How will I know if these light panels: http://www.amazon.co.uk/Neewer-Photography-Lighting-including-Camcorder/dp/B00LVTZH9I/ref=sr_1_3?ie=UTF8&qid=1426886125&sr=8-3&keywords=video+lights        are the same frequency as the 1200d at 1080p at 30FPS 

 

Probably have to google it 

[GeekaWhat]

Probably have to google it 

 

Because UK plugs output 50Hz if I film below that will I get flicker - or is it only when I try ad film above it?

[Kermit]

Because UK plugs output 50Hz if I film below that will I get flicker - or is it only when I try ad film above it?

 

No I think your correct

 

Just film in 60 fps and render in 30

[.spider.]

Unless it's the same frequency, they will always flicker on camera

No you can simply adjust the shutter angel until is is flicker free.

http://www.red.com/tools/flicker-free-video

Edit: But I'd guess the pwm frequency is far above 50Hz

[GeekaWhat]

No you can simply adjust the shutter angel until is is flicker free.

http://www.red.com/tools/flicker-free-video

Edit: But I'd guess the pwm frequency is far above 50Hz

 

That's super handy and now boomarked - you're an absolute life saver!