HELP!? High Frame Rate Flicker That I Can't Solve

[Adam Griffith]

Hi all,

I'm experiencing some flicker in my footage when I would otherwise not be expecting it. I'm aware of matching my frame rate/shutter to match that of the power source frequency of the lights to avoid such flicker - ie: 50hz power here in Australia means I should shoot at 25fps with a 1/50 (180*) shutter to avoid flicker, and any factor of 50 with the co-insiding shutter (maintaining 180 degree) should also be flicker free.

However I am not experiencing this. I've got a heavy flicker in the LCD as well as in the final recorded file.

Now for the twist...When the camera goes into power saving mode - The flicker goes away. Obviously you cant record in power saving mode so this is useless but can someone explain to me what is going on?!
I've messed up two shoots with this flicker that needed work to save because I hadn't noticed it before. I've got another coming and I need to find a fix or solid work around before then.

Here is a youtube video I shot on my iPhone showing the issue.
https://www.youtube.com/watch?v=eK5R5lvHyY0

 

[David Battistella]

What are you powering the camera from? Mains or Battery power?
Also, what is your shutter time?

David

 

[Adam Griffith]

Hi David,

powering camera from a RED BRICK (DC Source)
Shutter is 180 degree or 1/600th in this case of 300fps.

I've used the RED Flicker free tool and it says no shutter will help at 300fps but mathematically I can't understand why?

 

[Chris McKechnie]

Weird that going into power save gets rid of the issue. Have you tried resetting the camera by holding down the power button for about 20 seconds when the camera is off? Try that and see if it fixes your issue. Also, I would switch from whatever power method you're currently using to another one as David suggested.

If the footage is already in the can and you're trying to get rid of it, you can create layers in a timeline...both the exact same shot, then offset the top layer by 1 frame, change the blending mode to Screen, then adjust opacity as necessary.

 

[Adam Griffith]

hang on...I think I've had a mathematical epiphany. It's theoretically impossible due to the power cycling at 50hz (sine wave 50 times a second) and I'm trying to capture the light 300 times a second (300hz) but for only half the duration (180 degree shutter) meaning I'm going to capture the 50hz sine wave (the artificial light frequency) at different stages of its cycle so flicker is going to be obvious no matter what I do....

/end thread. sorry guys

 

[Adam Griffith]

Weird that going into power save gets rid of the issue.

My theory on this Chris is the LCD switches from a 300fps preview to a 25fps preview when in power saving mode...thus removing the flicker.
Someone from RED will have to confirm this one though.

I've done the math, seems I can only safely get away with double the power cycle ie: 50hz here in Australia - I can shoot 100fps cleanly, anything more shows flicker. This coincides with the RED flicker free calculator tool.

 

[Gunleik Groven]

I think you answered your own question...

Sorry

G

 

[Bérenger Brillante]

beyond 100-150 frame per second, it can flick, even if you have a match on everything.

That's why there are flicker free, 1/300 and 1/1000 modes on HMI ballast. the 1/1000 is what you should have use. The flicker free weirdly, flicks.

On tungsten sources, it's off course worse and can flick at 100img/s

I think the power saving mode switches to a 360° shutter or to less than 25 img/sec and so the 180° is actually longer than normal.

 

[Chris McKechnie]

My theory on this Chris is the LCD switches from a 300fps preview to a 25fps preview when in power saving mode...thus removing the flicker.
Someone from RED will have to confirm this one though.

I've done the math, seems I can only safely get away with double the power cycle ie: 50hz here in Australia - I can shoot 100fps cleanly, anything more shows flicker. This coincides with the RED flicker free calculator tool.

haha...didn't know you were recording at 300 fps...there's your answer. hehe

 

[David Battistella]

Math is Math, hard to get around that!

David

My theory on this Chris is the LCD switches from a 300fps preview to a 25fps preview when in power saving mode...thus removing the flicker.
Someone from RED will have to confirm this one though.

I've done the math, seems I can only safely get away with double the power cycle ie: 50hz here in Australia - I can shoot 100fps cleanly, anything more shows flicker. This coincides with the RED flicker free calculator tool.

 

[Brandon Shafto]

300fps
That's it mate. Nothing more to be done.

 

[Brandon Shafto]

You can try a lower fps and use Twixtor in post. Great results with frame rates above 60fps.

 

[Russ Fill]

Isn't there a decay or dimming of the light during the cycle with would over lap the exact 50th cycle?
In simpler terms the light can't go on and off at the exact same rate as the power cycle powering it. So it will dim/flicker no matter what you do. But at slower frame rates its less noticeable as the light can dim and brighten with less notice at the lower rates..

 

[Loic Parent]

take a look at RE/VISION de flicker :http://revisionfx.com/products/deflicker/after-effects/
it's crazy how great it works!