Edwin Street wrote:The 180º shutter rule applies only to standard frame rates, ie 23.976, 24, 25, 29.97, and 30.
If you're using high frame rates, ie 47.95, 48, 50, 59.94, and 60 you need to use a 360º shutter angle to replicate the same motion blurring as the low frame rates I mentioned above.
Other shutter angles:
In PAL land it is common to use a shutter angle of 172.8º for 24fps because of the lights we use so you don't see flicker.
Peter Jackson famously used a shutter angle of 270º to film The Hobbit films at 48fps.
No, not really.
180º shutter comes from when there was a rotating shutter in film cameras - it was literally a circular disk that rotate to control the light coming into the camera - the reason it is measured at an angle is because that was how much of the shutter disk was cut to allow for a certain passage of light: typically it was 180º, but if you wanted sharp action and less motion blur you'd use a smaller angle (like 90º), and if you wanted a "smear" effect, you'd use a wider angle (like 270º). Shutter angle was independent of framerates, and although the 180º shutter would spin at a higher speed at higher framerates, it was always a 180º shutter.
You can see the effect of using different shutter angles used as a storytelling in the opening battle scene of Ridley Scott's Gladiator: as the battle starts, the motion is super crisp with almost no motion blur; towards the end of the battle, there is more and more motion blur until the images become very unclear. This is a visual storytelling technique to indicate the rush of adrenaline at the start of a battle (crisp images) and the fatigue that sets in as the battle wears on (blurred motion). It's really brilliant, actually.
But back to shutter angle: a lot of filmmakers come from DSLRs, which don't use shutter angle, but shutter speed (a photography setting). Most of us learn that the 180º is "set your shutter speed to double your framerate" - this is in effect what the 180º shutter angle is, so that if you're shooting at 24 fps you set your shutter speed to 1/48 (typically 1/50). But if you're shooting higher frame rates like 60 fps, then your 180º shutter speed is 1/120 - that creates what is seen as "typical" motion blur that the audience is used to.
There are some small variations depending on light flickering, as you said, but overall the 180º shutter angle is what we consider "normal" motion blur, regardless of frame rate.
I hadn't heard that Jackson used a 270º shutter angle (I knew he shot in 48 fps) - but that also changes the motion blur and explains why the live action parts looked like a soap opera and the cgi looked like PS2 graphics (in my opinion) in the first Hobbit film. It was a little better in parts 2 and 3, but I saw the first one in High Frame Rate 3d, normal 3d, and 2d - and the 2d was actually the best for the first one (and I'm a fan of 3d when it's done well).