GoPro Hero8 flicker issue
Discussion
Hi,
I am experimenting with using a GoPro Hero8 Black inside road cars for advanced driving commentary etc. It works fine in its auto mode for racing/track work attached to a roll cage but I've come across this issue when used in car which I can't seem to find any answers to:
- The camera is mounted in the car, using a headrest mount. If I leave it on auto then the outside is over-exposed but I do not have any flicker issues with lights inside the vehicle. If I either use spot metering or reduce EV to sort this out then a few, but not all, lights inside the car flicker. This is seen on the GoPro directly and with any unedited video played back on any device. In a BMW, for example, the main iDrive and digital dash are fine but the light for the driver assistance features (conveniently right in the middle of the shot) flashes away like crazy. Equally if you turn on the interior lights they flicker away.
- I have tried adjusting the anti-flicker (to switch between NTSC and PAL), various different fps etc but it makes no difference (including at 50fps).
Any ideas gratefully received!
Thanks
Steve
I am experimenting with using a GoPro Hero8 Black inside road cars for advanced driving commentary etc. It works fine in its auto mode for racing/track work attached to a roll cage but I've come across this issue when used in car which I can't seem to find any answers to:
- The camera is mounted in the car, using a headrest mount. If I leave it on auto then the outside is over-exposed but I do not have any flicker issues with lights inside the vehicle. If I either use spot metering or reduce EV to sort this out then a few, but not all, lights inside the car flicker. This is seen on the GoPro directly and with any unedited video played back on any device. In a BMW, for example, the main iDrive and digital dash are fine but the light for the driver assistance features (conveniently right in the middle of the shot) flashes away like crazy. Equally if you turn on the interior lights they flicker away.
- I have tried adjusting the anti-flicker (to switch between NTSC and PAL), various different fps etc but it makes no difference (including at 50fps).
Any ideas gratefully received!
Thanks
Steve
It's to do with the refresh rate of the camera sensor and that of the incar screen and LEDs, anti flicker mode applies to normal lights connected to mains power.
Not sure if there's much that can be done as even professionals filming of cars in shows such as Top Gear and Grand tour can't seem to handle recording modern LED brake lights which use PWM causing it to look like the lights are rapidly blinking, especially noticeable in slomo shots.
Edit: something that may help dependant if you want the screen to be less noticeable would be to fit a CPL filter to the GoPro then change the angle of polarisation till the screen isn't visible, would also help cut down on reflections out the windscreen as well.
Not sure if there's much that can be done as even professionals filming of cars in shows such as Top Gear and Grand tour can't seem to handle recording modern LED brake lights which use PWM causing it to look like the lights are rapidly blinking, especially noticeable in slomo shots.
Edit: something that may help dependant if you want the screen to be less noticeable would be to fit a CPL filter to the GoPro then change the angle of polarisation till the screen isn't visible, would also help cut down on reflections out the windscreen as well.
Edited by untakenname on Sunday 9th August 18:28
It's to do with the refresh rate of the camera sensor and that of the incar screen and LEDs, anti flicker mode applies to normal lights connected to mains power.
Not sure if there's much that can be done as even professionals filming of cars in shows such as Top Gear and Grand tour can't seem to handle recording modern LED brake lights which use PWM causing it to look like the lights are rapidly blinking, especially noticeable in slomo shots.
Edit: something that may help dependant if you want the screen to be less noticeable would be to fit a CPL filter to the GoPro then change the angle of polarisation till the screen isn't visible, would also help cut down on reflections out the windscreen as well.
Not sure if there's much that can be done as even professionals filming of cars in shows such as Top Gear and Grand tour can't seem to handle recording modern LED brake lights which use PWM causing it to look like the lights are rapidly blinking, especially noticeable in slomo shots.
Edit: something that may help dependant if you want the screen to be less noticeable would be to fit a CPL filter to the GoPro then change the angle of polarisation till the screen isn't visible, would also help cut down on reflections out the windscreen as well.
Edited by untakenname on Sunday 9th August 18:28
LED's can be a pain with flicker.
To add to the info people have already mentioned -
The prob with LED's, is each group of LEDs is run by its own electric driver, and flickers at a different rate. - The 'anti-flicker mode', most likely tries to lock the go pros shutter speed to a multiple of 50, so it's in line with 50hz of AC power in the uk, which would get rid of flicker seen in tungsten lights plugged into mains - but sadly not with LED's in a car.
I've worked on some documentaries on ships, and they have their own AC generator which often isn't as precise as main electricity, and can have a slightly faster or slower AC cycle rate than 50 or 60hz - so with a pro camera, you can often fine tune the shutter speed to precisely match the frequency of the ships AC grid. I used to like used Sony's pro cameras as they had an 'ECS' shutter mode, where you could infinity vary the shutter - you'd just keep ramping it up and when the flicker stops, you'd be set. So you'd end up working at a shutter of 1/61.33. for example.
Back to gopros! - So go pros don't really have a variable iris, they vary exposure by ramping up or down the shutter speed. - It could be a high shutter from the GoPro that's causing the flicker.
So one thing that could help, is to purchase an ND filter set for the Gopro. An ND will mean the GoPro will revert to a lower shutter, and the flicker might go away.
As a bonus, I think ND's can really improve GoPro footage from the exterior of a car. Bright days mean the shutter on the gopro is super high, so movement, like the tarmac and scenery zipping by, don't get natural motion blur, so the shot can look a bit stuttery. The ND helps drop the shutter to a more normal speed, and you get natural looking motion blur which makes the shots feel a bit more natural.
To add to the info people have already mentioned -
The prob with LED's, is each group of LEDs is run by its own electric driver, and flickers at a different rate. - The 'anti-flicker mode', most likely tries to lock the go pros shutter speed to a multiple of 50, so it's in line with 50hz of AC power in the uk, which would get rid of flicker seen in tungsten lights plugged into mains - but sadly not with LED's in a car.
I've worked on some documentaries on ships, and they have their own AC generator which often isn't as precise as main electricity, and can have a slightly faster or slower AC cycle rate than 50 or 60hz - so with a pro camera, you can often fine tune the shutter speed to precisely match the frequency of the ships AC grid. I used to like used Sony's pro cameras as they had an 'ECS' shutter mode, where you could infinity vary the shutter - you'd just keep ramping it up and when the flicker stops, you'd be set. So you'd end up working at a shutter of 1/61.33. for example.
Back to gopros! - So go pros don't really have a variable iris, they vary exposure by ramping up or down the shutter speed. - It could be a high shutter from the GoPro that's causing the flicker.
So one thing that could help, is to purchase an ND filter set for the Gopro. An ND will mean the GoPro will revert to a lower shutter, and the flicker might go away.
As a bonus, I think ND's can really improve GoPro footage from the exterior of a car. Bright days mean the shutter on the gopro is super high, so movement, like the tarmac and scenery zipping by, don't get natural motion blur, so the shot can look a bit stuttery. The ND helps drop the shutter to a more normal speed, and you get natural looking motion blur which makes the shots feel a bit more natural.
You could try this:
In post, duplicate the clip and set the duplicate above the same clip in the time line, setting volume to zero. Off-set the duplicate by one frame and set to 50% opacity - trim the spare frame at the beginning and end of the respective clips.
Tends to work with single source LEDS but may improve what you have.
In post, duplicate the clip and set the duplicate above the same clip in the time line, setting volume to zero. Off-set the duplicate by one frame and set to 50% opacity - trim the spare frame at the beginning and end of the respective clips.
Tends to work with single source LEDS but may improve what you have.
Gassing Station | Photography & Video | Top of Page | What's New | My Stuff