Shutter angle questions

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David Evans

Well-known member
Hi guys,

Just two quick questions concerning shutter angles:

1 - when shooting at 25fps, shutter speed (for cinematic shooting) should be 1/50. This should be 172 in shutter angle or should it be kept at 180?

2 - if shooting real estate or generic videos at 60fps (slowed down to 25fps), where do you guys set your shutter angles at for smooth shots?

Thanks!
 
legrevedotcom said:
1. would be 180
2. 180, because it would be relative to the fps, in this case 1/120s.
Click to expand...

Thanks. I didn't understand the 1/120 that you mentioned. What would be the smoothest setting that is generally used for slow mo real estate and similar projects? Sorry to ask but I usually just work in narrative (which is always 25fps).

Thanks
 
Always 180, that saves you having to worry about the math in the heat of a fast paced shoot. Unless you want some special look with smeary slower shutter or strobey looking fast shutter, 180 is the default.
 
No, it's not that simple. Blur is a function of shutter speed and motion. If you're one of those people always in pursuit of 180 degree motion blur in your display footage, i.e. 1/50th shutter at 25fps, you have to shoot as close as you can get to that for your display angle/speed, which in your case is 360 degrees (1/50th) at 50fps or above. If you've got one of the rare cameras that shoot greater than 360 degrees, unless you want the smear, don't. If you're after cinematic, 172 degrees is closer to what most film cameras shot, 180 was just a theoretical maximum for most common film camera shutters in those days.
 
legrevedotcom said:
in this case 1/120s.
Click to expand...

For smooth motion, i.e. most cinema like blur on moving objects, a 180 degree shutter has been traditional for over a century, and is considered the norm. What 180 degrees really is - is one half of the shutter (a full 360 degree circle) being cut away, or open, and the other half is a thin piece of sheet metal, which is solid and blocks the light. As the motor turns the sprockets and gears, the shutter spins, one half of the time being open, exposing the film, and the other half of the time being closed, allowing the pull down to advance the film to the next frame. That's the key thing to remember, one half, or 1/2. So now calculating shutter speed is relatively easy. It's the reciprocal of double the frame rate, which sounds like some scary math. It isn't. Just double the frame rate, draw a line over it, and draw the number 1 above that.

So for your theoretical 60 frames per second - 2 x 60 = 120. With a 1 over it = 1/120th of a second. Easy as pie. So many people get so confused over something extremely simple. Digital systems have no need to block the light with a physical shutter. They simply stop reading the light, dump the frame to memory, clear the sensor, and begin reading the light again. Digital systems can actually use shutter speeds that are Longer than those recommended by the 180 (one half) rule. They can easily go to speeds which are the equivalent of a 360 degree shutter, which would be constantly open, never blocking the light. You can't get to shutter speeds longer than the reciprocal of the frame rate though, i.e. 60 frames per second equals a theoretical maximum of 1/60th of a second.

The actual math is shutter angle/360 x 1/Frame Rate. With this you can go for the "narrow shutter" look, like "Gladiator" or "Saving Private Ryan". Say you're shooting at 24 frames per second and want a 25 degree shutter.

25/360 x 1/24 = 0.0694 x 0.04166 = 0.00289 or about 3/1000's of a second. It's that Short exposure time that gives "Private Ryan" it's staccato, no blur look on screen.

What about wider shutters? No problem. Let's try 300 degrees at 30 frames per second. 300/360 x 1/30 = 0.83333 x 0.03333 = 0.027777 or about 28/1000's of a second, which blurs more than the 1/48 second, or 0.02083 or 21/1000's of a second for 24 frames at 180 degrees, and yes, that extra 7/1000ths of a second does give more blur and a different "look" to the images.
 
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David Evans said:
Hi guys,

Just two quick questions concerning shutter angles:

1 - when shooting at 25fps, shutter speed (for cinematic shooting) should be 1/50. This should be 172 in shutter angle or should it be kept at 180?

2 - if shooting real estate or generic videos at 60fps (slowed down to 25fps), where do you guys set your shutter angles at for smooth shots?

Thanks!
Click to expand...

180 degrees = double the shutter speed

But you need to consider if your region has 50KHz or 60KHz lighting, and teak your shutter speed slightly to match that.
 
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