Flicker problem above 100FPS

[Filipo]

Hello,

I have flicker problem above 100FPS.
The shutter speeds are correct.

What should i do?

 

[Jeff Kilgroe]

What sort of lights are you shooting with?

Can you post a clip so we can see what you're talking about. Try shooting outdoors in sunlight and see if you still have your flicker.

 

[Filipo]

It was halogen 650W 3200K light source. I saw flicker problem on the white wall and on the highlights.

You will get tomorrow outside and inside tests.

Thanks

 

[Petros Nousias]

I've had flicker problems as well, tungsten only. Last time was yesterday with photoflood on a dimmer. 24fps, 1/40 shutter. Another time at 100fps, normal halogen lamp. Yet another with a street lamp, 24fps, 1/48 shutter. If I remember correctly it has to do with the rolling shutter. Shame...

 

[Deanan]

For light sources that can pulse, try to keep your shutter speed (and ideally your framerate too) to a multiple of your countries AC frequency. So for the US, 1/30th, 1/60th, 1/120th, etc. Or use flicker-free lightsources.

 

[Stephen Williams]

Hi,

The problem is a physically small lamp, you are seeing it heat up & cool down. At 150 fps I don't recomend less than a 5K, a 2K is borderline for sure. Avoid electronic dimmers at all cost!

Stephen

 

[Harry Clark]

I think Stephen is right. Small filaments heat up and cool down with each AC pulse, but the flicker is normally very slight. High speeds exacerbate this.
Some stages are wired for either AC or DC. I know the sound department always prefers DC because it eliminates the "singing" of larger unit bulbs with AC.
Alas, no light is perfect except for the sun!
Cheers,
Harry

 

[Mitch Gross]

This may be of use to you. It is from the FAQ I wrote about the Phantom HD for our website.


Lighting for High-Speed


Lighting issues are not specific for the Phantom cameras but for high frame rate photography in general. Even with the great sensitivity of modern cameras, be prepared to use a considerable amount of light. Beyond illumination, the largest issue in high-speed lighting is flicker. Tungsten lights actually have a flicker rate. When powered by alternating current (AC) electricity, the power cycles 50 or 60 times per second (depending on the country and its power system). During the down cycle the tungsten lamp filament can dim slightly, causing flicker. The amount of dimming is related to the type of bulb, wattage and physical size of filament. In general, we have found that lamps larger than 2000 watts use tungsten filaments so large that they do not have time to cool and dim before the power cycles back up. Therefore, we recommend using 2K or greater tungsten light fixtures when shooting above 120fps (100fps in 50hz countries). Be aware that a nine-light is NOT a large light but is actually an array of smaller light and as such can flicker.

Some additional recommendations are to use DC power for tungsten lights, which eliminates flicker entirely. HMI and fluorescent lights are generally fine for speeds under 120fps as long as they use electronic ballasts. Magnetic ballasts should not be used. HMI lights can suffer from “arc wander,” whereby a plasmatic “hot spot” can move about within the bulb, causing an amorphous shifting movement in the light output. LED lights are subject to the electronic circuits driving them and are subject to a vast array of refresh rates. Finally, the shutter angle on the Phantom can affect flicker as well, as a greater shutter angle allows for a longer response time from the light. When shooting extremely high frame rates, it may no longer be necessary to retain a 180-degree shutter to capture the motion generally preferred for a filmic look. A 360-degree shutter allows both more light sensitivity and reduced flicker possibilities.