Shutter Angle with Overcranking

[Jonathan Stevenson]

Hello all,

I'm wondering if anyone can discuss the effects on the image when you combined high frame rates with an altered shutter angle.

For example, 24fps combined with the 1/120 shutter has that "on crack" look. Everything looks very staccato, action is very pronounced, shaky, etc. So I'm curious as to what effect the shutter angle has on slow motion footage (i.e. 120fps with 1/120). Does it make it smoother? Does it make it jumpy and jittery also? What about 120 fps at 1/60, or even 1/250?

Videos would be awesome if anyone has any. Thanks folks!

Edit: I don't currently have a Red for testing any of this.

 

[Leo Ticheli]

I've not had my coffee yet, so maybe I'm missing something, but, Jonathan, I will be very impressed if you can find a way to put a 1/60 second duration into a space that's 1/120 second long.

The effects of frame rate and shutter angle are best determined by test and entirely dependent on what you're trying to say with your scene. The demands of a fight scene, for example, are probably quite different from a lyrical, romantic ballet.

Why don't you just experiment?

Good shooting and best regards,

Leo

 

[Jeff Kilgroe]

Experimentation is always the best way to determine what you want to use. When you talk about shutter speed, it's OK to relate in actual speed as you are doing, but thinking of it in terms of angle or percentage can be useful too when shooting off-speed (over/under - cranked).

If you are shooting 24fps with a 180 deg. shutter, which is pretty typical, think of the shutter as 50% or 1/48s. If you overcrank to 96fps and allow the camera to maintain a "relative" shutter speed, it remains 180 degrees or 50%, but exposure time is decreased to 1/192s. This will maintain similar motion blur properties to your regular 24fps footage, but everything will be moving 1/4 normal speed. By further decreasing the exposure time or shutter angle/%, you decrease the amount of motion blur.

24fps with 1/120 shutter does have that stroby, staccato, no-blur effect. However, If you shoot 120fps with a 1/120s shutter, you have effectively made your exposure time the same as your frame duration, which is a 360 degree shutter. You will have very smooth images with lots of blur.

Maintaining a relative shutter speed when overcranking is typical, to achieve similar blur properties, but to slow down the motion. Sometimes, depending on the desired look, longer exposure times can smooth out or blur the image for a more dream-like effect. When undercranking, to give the appearance of faster motion, it is typically desirable to use a longer exposure time for more blur. That way, when the motion is played back at the intended rate, the additional blur smoothes the motion and makes it seem as if it happened faster than it really did.

Experiment, play, test, test, test...

 

[Jonathan Stevenson]

Thanks Jeff. Unfortunately all I have now is my HVX which can certainly do these types of settings but I wasn't sure if it was a true representation of what would happen in a Red or film camera. But you definitely answered my question.

Thanks!

 

[Steve Gibby]

For certain RED One projects I shoot a lot of overcranked footage for slo-mo purposes - sports, nature, etc.

Assuming your project frame rate is 23.98, and you're using Varispeed to overcrank, here's some ideas with RED One: (all figures offered by memory. If the camera manual says other figures possible, by all means test them out)

In 4k, with a project frame rate of 23.98, the highest Varispeed frame rate you can get is 30fps, a mere 6.02fps overcrank. If you're shooting high motion subjects and need to smooth out the action and slow it down slightly on playback, then 30fps can get you a little bit of that. For that I've had good results setting the shutter at 96th sec or 105th sec.

In 3k, with a project frame rate of 23.98, the highest frame rate you can get is 50fps in Varispeed. I've had good slo-mo results with a project frame rate of 23.98, 48fps in Varispeed, and a shutter of 120th sec

In 2k, with a project frame rate of 23.98, in Varispeed the max frame rate is 120. I've had good slo-mo results with a project frame rate of 23.98, Varispeed frame rate of 120, and a shutter of 196th sec.

As Leo wisely advised, shoot lots of test footage, then check out the QT proxies. If you set the project frame rate, then use Varispeed to overcrank, when you play back the proxies they will play at the project frame rate and you can see how your slo-mos look.

Hope this helps...

Edit: I see Jeff is a faster typist than me

 

[Stefan Scherperel]

Just a technical note to Gibby's post, at 3K your highest frame rate is 60fps. Although at redcode 36, 50fps is your max in 3K.

 

[Steve Gibby]

Just a technical note to Gibby's post, at 3K your highest frame rate is 60fps. Although at redcode 36, 50fps is your max in 3K.

Yes, good catch on that...

If RedCode 28 will suffice, higher frame rates are available than when shooting RedCode 36. Its the tradeoff between slightly higher frame rates with slightly less quality, or the opposite, slightly lower quality and slightly higher frame rates. That's a question we need to ask ourselves about the needs of each project.

 

[Ivan Cortazar]

Hi all,

I have been trying to get 24fps at 1/24th (360 degree angle) and I can only get it with Varispeed mode. Is that correct or I am missing something?. If that is the case, it is quite inconvenient, because in Varispeed mode it doesn't record sound. So the "emergency light kit I need an extra stop solution" doesn't really work. Of course unless it is a silent movie or you have an extra person recording sound externally... ::unhappy:

 

[Dominic Jones]

You've probably got your EVF mode set to "open gate". That locks you out of >180 degree shutter settings...

HTH,
Dom.

 

[MattGahan]

"24fps with 1/120 shutter does have that stroby, staccato, no-blur effect. However, If you shoot 120fps with a 1/120s shutter, you have effectively made your exposure time the same as your frame duration, which is a 360 degree shutter. You will have very smooth images with lots of blur"

isn't 1/120 of a second the same amount of time no matter what the frame rate? Wouldn't the amount of motion blur be the same?

 

[Jeff Kilgroe]

isn't 1/120 of a second the same amount of time no matter what the frame rate? Wouldn't the amount of motion blur be the same?

Yes, same amount of blur per frame as the exposure times are the same. But the end effect is different because of the different acquisition rates.

When you capture a 1/120th of a second exposure every 1/24th of a second, there is still 0.8 seconds of motion not accounted for! When you record 120 of those 1/120th of a second exposures within a second, the entire second of motion is accounted for. If you play back all frames recorded for each frame rate at 24fps. The 24fps acquired footage has the appearance of very little blur, jumpy and stuttery. The 120fps acquired footage is smooth, the blur of one frame blends to the blur of the next, all the motion is accounted for, it just plays at 1/5th the acquired speed. Obviously, if you take the 120fps footage and only play every 5th frame, then it will play at real time and will have the same stuttery motion as if you acquired it at 24fps with the 1/120s shutter. Because that's just what it is.

when I said "lots of blur" above, that is relative to the format being shot, sensitivity of the film stock or sensor, etc.. A 360 degree or open shutter at 120fps is "a lot of blur" for shooting 120fps. But a 1/120s exposure for something being shot at 24fps is not much blur at all.

 

[MattGahan]

Ok, that makes sense. I guess I was imagining looking at a still from each scenario rather than looking at the images in motion. Thanks for the explanation.