Flickering is a constant struggle for bullet-time systems. Here are a few tricks to reduce or even eliminate flickering.
What causes flickering?
- Fluorescent lights (stay away from that!)
- Old cameras (lazy shutter)
- Fast shutter speed
- Flare (lights facing the cameras)
- Flash speed
- Dirty lenses
What are the solutions?
- When using flashes
The best solution to avoid flickering is to use strobes / flashes / speedlites. This is what I did in this example: https://www.instagram.com/p/Bxipx5rFswp/.
However, even with flash, you might get some flickering if the light is strobing too fast. Your best option with flashes is always to use a 1/60s shutter speed and a longer duration flash. When using legit Canon 600ex Speedlite, you are 100% sure of never having cameras that are missing the light as the flashes are slow enough to cover the whole exposure. But when using super-powerful lights like the Profoto D2 1000w, you are going to see flickering if you use the light at a lower value. The reason is that these lights are not dimming but instead, they play with the duration to provide more or less light. When you go to 100% power, then your flash lasts just long enough to get picked up by all cameras.
Why is it always a better solution to use flashes? By doing this, you are not relying on the physical camera shutter, but instead, it's the light that syncs the subject. There's nothing faster than light, right? :)
- When using constant light
Most of the flickering problems are happening when using constant lights. This is caused most of the times by shutter inaccuracy. Shutter speed is not accurate when working with basic Canon DSLRs. When you shoot at 1/60s, all cameras are going to be able to give you that exact speed, but as soon as you go over 1/200s, you'll start to see dark frames. It is especially visible when you go at super fast shutter speed like 1/4000s. The older your cameras get, the more flickering you are likely to have. Over time, the shutter becomes lazy
The sweet spot is a shutter speed of 1/200s. That means that you are likely to see a little bit of blur if your subject is moving fast, but you'll reduce the flickering.
If only one of your cameras is giving you a brighter frame, you can simply swap it for another one.
- Clean your lenses (Both ends!)
This seems like a long stretch, but we had an issue recently with one of our 176 cameras being way brighter than the other ones. We ended up finding that the inside of the lens had a finger print on it! Always clean your lenses to avoid flickering due to smudge.
- Deflickering in Adobe Premiere (for studio work)
If you're shooting high end studio work in RAW, you can always deflicker in Adobe Premiere using RE:Vision DEFlicker Auto Levels. It works well, but it takes forever to process