Shooting slow motion footage, especially very high speed shots like 240fps or 480fps, results in flicker if you don’t have high quality lights. Stadiums often have low quality industrial lighting, LEDs, or both. Resulting in flicker during slow motion shots even on nationally broadcast, high profile sporting events.
I was particularly struck by this watching the NCAA Basketball Tournament this weekend. Seemed like I was seeing flicker on half of the slow motion shots. You can see a few in this video (along with Flicker Free plugin de-flickered versions of the same footage):
The LED lights are most often the problem. They circle the arena and depending on how bright they are, for example if it’s turned solid white, they can cast enough light on the players to cause flicker when played back in slow motion. Even if they don’t cast light on the players they’re visible in the background flickering. Here’s a photo of the lights I’m talking about in Oracle arena (white band of light going around the stadium):
While Flicker Free won’t work for live production, it works great for de-flickering this type of flicker if you can render it in a video editing app, as you can see in the original example.
It’s a common problem even for pro sports or high profile sporting events (once you start looking for it, you see it a lot). So if you run into with your footage, check out the Flicker Free plugin for most video editing applications!
Unfortunately, I’m usually limited to shooting from the stands. So this makes the process a little harder but if you can get good seats you can make it work. As it happens, I recently got third row seats to the Golden State Warriors game against the Lakers. So here are a few tips for getting great shots if you can’t actually get a press pass.
The first thing you need to check is how long of a lens you’re allowed to bring in. In this case it was a 3″ or less. So that’s what needs to be attached to the camera. (see the end of the article for some ‘other’ suggestions)
I ended up using a 100mm f2 lens for these shots, which is exactly 3″. You want as fast of a lens as possible. You’re not going to be able to use a flash, so you’re reliant on the stadium lighting which isn’t particularly bright. f2.8 is really a minimum and even then you’ll have the ISO higher than you’d like. Like wildlife, the action moves fast, so the wider the aperture, the faster the shutter speed you’ll have, and the sharper the shots will be.
The minimum shutter speed is probably about 1/500 and you’d like 1/2000 or higher. Hence the need for a f2 or f2.8 lens. Otherwise, the action shots, where you really want it to be sharp, will be a bit blurry.
Seat placement matters. Obviously you want to be as close as possible, but you also want to be at the ends of the court/field. That’s where most of the action happens. Center court seats may be great for watching the game, but behind the goal seats get you up close and personal for half of the action. Much better for photography and hence one of the reasons the press photogs are on the baseline.
What if you’re not happy with a 3″ lens? Well, you COULD give a friend a larger lens and let them try and smuggle it in. Since it’s not attached to the camera, most of the security people don’t recognize it as a camera lens. Just say it’s, you know, a binocular or something (monocular? ;-). Usually it works, worst thing that happens is you have to go back to the car and store it. You’re not trying to break the rules, you’re, uh, helping train the security staff.
If you do manage to get a larger lens in, don’t expect to be able to use it much. One of the ushers will eventually spot it (especially if it’s a big, white, L Canon lens) and call you on it. You’ll have to swap it for the other lens (or risk getting kicked out). Wait until the game is well underway before trying to use it.
Of course, the basic tips apply… Shoot RAW, make sure you have a large, empty memory card(s), a fully charged battery, don’t spill beer on the camera, etc., etc. But the critical component is getting close to the end of the court and having a very fast shutter speed (which usually means a very wide aperture).
Shooting RAW is soooo critical. It’ll give you some flexibility to adjust the exposure and do some sharpening. Since you’ll probably have a relatively high ISO, the noise reduction capabilities are important as well. Always shoot RAW.
If you’re a photographer that loves sports, it is definitely fun to get good seats and work on your sports shooting skills. Can be a bit expensive to do on a regular basis though!
One common problem you see a lot is flickering from stadium lights when football or other sports are played back in slow motion. You’ll even see it during the NFL football playoffs. Stadium lights tend to be low quality lights and the brightness fluctuates. You can’t see it normally, but play video back at 240fps… and flicker is everywhere.
Aaron at Griffin Wing Video Productions ran into this problem shooting video of the high school football championship at the North Carolina State stadium. It was a night game and he got some great slomo shots shooting with the Sony FS700, but a ton of flicker from the stadium lights.
Let’s take a look at a couple of his examples and break down how our Flicker Free plugin fixed the problem for him.
First example is just a player turning his head as he gazes down on the field. There’s not a lot of fast movement so this is relatively easy. Here are the Flicker Free plugin parameters from within After Effects (although it works the same if you’re using Premiere, FCP, Avid, etc.)
Notice that ‘Detect Motion’ is turned off and the settings for Sensitivity and Time Radius. Well discuss those in a moment.
Here’s a second example of a wide receiver catching the football. Here there’s a lot more action (even in slow motion), so the plugin needs different settings to compensate for that motion. Here’s the before/after video footage:
Here are the Flicker Free plugin settings:
So, what’s going on? You’ll notice that Detect Motion is off. Detect Motion tries to eliminate the ghosting (see below for an example) that can happen when removing flicker from a bunch of frames. (FF analyzes multiple frames to find the correct luminance for each pixel. But ghosts or trails can appear if the pixel is moving) Unfortunately it also reduces the flicker removal capabilities. The video footage we have of the football team has some pretty serious flicker so we need Detect Motion off.
With Detect Motion off we need to worry about ghosting. This means we need to reduce the Time Radius to a relatively low value.
Time Radius tells Flicker Free how many frames to look at before and after the current frame. So if it’s set to 5, it’ll analyze 11 frames: the current frame, 5 before it, and 5 after it. The more frames you analyze, the greater the chance objects will have moved in other frames… resulting in ghosting.
With the player looking our the window, there’s not a lot of motion. Just the turning of his head. So we can get away with a Time Radius of 5 and a Sensitivity of 3. (More about Sensitivity in a moment)
The video with the receiver catching the ball has a LOT more motion. Each frame is very different from the next. So there’s a good chance of ghosting. Here we’ve set Time Radius to 3, so it’s analyzing a total of 7 frames, and set Sensitivity to 10. A Time Radius of 3 is about as low as you can realistically go. In this case it works and the flicker is gone. (As you can see in the above video)
Here’s an example of the WRONG settings and what ‘ghosting’ looks like:
Sensitivity is, more or less, how large of an area the Flicker Free plugin analyzes. Usually I start with a low value like 3 and increase it to find a value that works best. Frequently a setting of 3 works as lower values reduce the flicker more. However, low values can result in more ghosting, so if you have a lot of motion sometimes 5 or 10 works better. For the player turning his head, three was fine. For the receiver we needed to increase it to 10.