Barry_Green
Moderator
There are two different things at work here. Even in the title of the message you mention strobing/aliasing -- they're not the same thing. Strobing is the choppy movement -- that will happen on any and every camera that shoots 24fps, always and forever, whether it's film or an F35, an Alexa or an HV20. A slow capture rate, combined with fast motion, = jerky/choppy footage. Always.
Aliasing leads to the stair-stepping that you were seeing on the 7D. The AF100 is largely immune to it, not 100% but it's incredibly much better.
If you want to absolutely avoid strobing in all situations, shoot 60p. If you want to shoot 24p and avoid strobing, you have to shoot like film shooters do -- slow down the camera motion, and follow a subject so the viewer has something relatively stationary on screen to keep their attention so they don't focus on the wildly-strobing background.
(and when I say "slow down your motion" -- I'm not kidding. I mean SLOW down your motion. The American Society of Cinematographers publishes a chart in the American Cinematographer's Manual that lists what panning speeds you can use to avoid strobing when shooting 24fps film. I adapted their chart for the AF100 Book. Depending on what focal length you're using, it might require 15 seconds to do a 90-degree pan... or it might require two minutes to do a 90-degree pan! And that's just 90 degrees. That's the chart based on the collected wisdom of over 100 years of professional cinematographers shooting 35mm and 16mm motion picture film, and those are their recommendations for how to avoid strobing.)
A simple rule that doesn't need a chart is this: an object should take 7 seconds to cross the screen. If it crosses the screen in less than 7 seconds, it's going to strobe. If it takes 7 seconds or more to go from one edge of the screen to the other, it will be smooth. And that rule applies for any 24p camera, whether it's film or an AF100, whether it's a Red One or an F35 or an Alexa or an F3 or a Z7U or an HV40 or an XHA1. 7 seconds.
Study how cinematographers compose and follow shots. And emulate how the best ones do it. Watch some films where there's motion and see how they do it -- watch how they control the angle of motion, and how they use the composition to direct the viewer's eye to keep the strobing from being the center of attention.
Of course, if your production doesn't "need" the 24p look, then you can take off the handcuffs and shoot 60p and get glassy smooth, fluid motion at all times.
Aliasing leads to the stair-stepping that you were seeing on the 7D. The AF100 is largely immune to it, not 100% but it's incredibly much better.
If you want to absolutely avoid strobing in all situations, shoot 60p. If you want to shoot 24p and avoid strobing, you have to shoot like film shooters do -- slow down the camera motion, and follow a subject so the viewer has something relatively stationary on screen to keep their attention so they don't focus on the wildly-strobing background.
(and when I say "slow down your motion" -- I'm not kidding. I mean SLOW down your motion. The American Society of Cinematographers publishes a chart in the American Cinematographer's Manual that lists what panning speeds you can use to avoid strobing when shooting 24fps film. I adapted their chart for the AF100 Book. Depending on what focal length you're using, it might require 15 seconds to do a 90-degree pan... or it might require two minutes to do a 90-degree pan! And that's just 90 degrees. That's the chart based on the collected wisdom of over 100 years of professional cinematographers shooting 35mm and 16mm motion picture film, and those are their recommendations for how to avoid strobing.)
A simple rule that doesn't need a chart is this: an object should take 7 seconds to cross the screen. If it crosses the screen in less than 7 seconds, it's going to strobe. If it takes 7 seconds or more to go from one edge of the screen to the other, it will be smooth. And that rule applies for any 24p camera, whether it's film or an AF100, whether it's a Red One or an F35 or an Alexa or an F3 or a Z7U or an HV40 or an XHA1. 7 seconds.
They will start strobing again. You can't cheat physics. If you try to convey too much motion in too few motion samples, it's gonna be jerky.
Study how cinematographers compose and follow shots. And emulate how the best ones do it. Watch some films where there's motion and see how they do it -- watch how they control the angle of motion, and how they use the composition to direct the viewer's eye to keep the strobing from being the center of attention.
Of course, if your production doesn't "need" the 24p look, then you can take off the handcuffs and shoot 60p and get glassy smooth, fluid motion at all times.
