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Frame Rate vs Shutter Angle - CONFUSED!

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 Frame Rate vs Shutter Angle - CONFUSED! on Oct 26, 2012 at 4:22:30 pm

Hi All,

I might be asking some incredibly amateurish questions here but please but patient, I'm learning! I'm planning to shoot some light trails with a RED epic and have been doing some tests in after effects. I'm struggling to understand the relationship between shutter speed, shutter angle and frame rate. Can I shoot at a frame rate that's higher than the shutter speed (and angle)? I'd like to allow for some motion blur with moving lights but keep the shutter speed nice and fast to create light trails with an LED. I'm sure it's possible, I just need to work it out!
Here's a link to a diagram which might explain more clearly. or confuse the issue...

4851_example.jpg.zip

 Re: Frame Rate vs Shutter Angle - CONFUSED!on Oct 26, 2012 at 5:06:47 pm

When you have chosen 250FPS, you have in effect chased 1/250th of a second as your shutter speed, even if you enter relative or absolute shutter mode on the EPIC the 250FPS will always mean that your basic shutter anlge will be 1/250th of a second.

You can, in effect choose higher shutter speeds (if you have the light to do so) but you can not select slow shutter and high frame rates.

I'm not even sure you could do this on film.

You might want to try to change the frequency of the lighting to achieve this.

David

______________________________
Lord Herbert
http://www.davidbattistella.com

 Re: Frame Rate vs Shutter Angle - CONFUSED!on Oct 29, 2012 at 4:27:56 pm

Hi David, That's what I had come to understand until I came across this video - http://blog.vincentlaforet.com/2010/12/01/famous-footwear-neighborhood/
The frame rate is listed at 600fps with a shutter angle of 360 degrees. I'm not sure how this possible!

 Re: Frame Rate vs Shutter Angle - CONFUSED!on Oct 30, 2012 at 1:53:19 pm

[Charlie Johnson] "Hi David, That's what I had come to understand until I came across this video - http://blog.vincentlaforet.com/2010/12/01/famous-footwear-neighborhood/
The frame rate is listed at 600fps with a shutter angle of 360 degrees. I'm not sure how this possible!"

Correct,

With the Phantom you can shoot 359degree shutter at 600fps.

One of the other factors here is electronic shutter over a traditional spinning shutter which can allow for an actual 360degree shutter. Because the electronic shutter scans from top to bottom you have to take into consideration the scan time (which is also the thing that causes jello images and skew in motion).
If you want those lights to make streaks you could set the camera to a 360 degree shutter and then capture at 24fps (allowing more light onto the sensor and getting that treaky effect.

however, you are going against physics by asking the camera to open at close the shutter at a high rate of speed (once per every frame at 250 frames per second or 250 time per second AND asking it to allow more light on the sensor at the same time.

Thisyou might want to create this as a composit shot.

pass one for action at 250FPS
Pass two for background action on the lighting.

Either way it is complicated. AFter effects is actually acting correctly and simulating exactly what a camera would do.

For an interesting lesson in a one degree shutter angle and what can be achieved, look at this spot and what some of my friends did with a film camera, a car at 50mph, a very long storyboard taped to a wall to create and amazing in camera effect.

David

______________________________
Lord Herbert
http://www.davidbattistella.com

 Re: Frame Rate vs Shutter Angle - CONFUSED!on Oct 26, 2012 at 6:30:51 pm

[Charlie Johnson] " I'm struggling to understand the relationship between shutter speed, shutter angle and frame rate. Can I shoot at a frame rate that's higher than the shutter speed (and angle)?"

Shutter speed is the amount of time the shutter is open to expose the sensor / media.

Frame rate is the number of frames per second.

Shutter angle (in degrees) is the film equivalent to shutter speed and is used by most professional systems.

the longer the shutter is open during the exposure the longer your trails will be

I work in shutter angles, you can find the conversion math on wikipedia

at 24 /25 fps a normal shutter is at 180* (degrees) which is 1/48 or 1/50 of a second. ( shutter is exposing for 1/2 of the frame rate)

for longer trails you should test at 240* 320* or Open
Electronic shutters allow for an "open" setting but it is not technically full open as a 360* film shutter would be. it is not the same look as one would find with a Pro camera doing the same.

you might also try slower frame rates with a longer opening to the shutter too.

Studio37

Post and Production Workflow Consultant
Production and Post Stereographer
Chicago, IL

http://blogs.creativecow.net/24640

 Re: Frame Rate vs Shutter Angle - CONFUSED!on Oct 26, 2012 at 6:32:17 pm

[Charlie Johnson] " I'm struggling to understand the relationship between shutter speed, shutter angle and frame rate. Can I shoot at a frame rate that's higher than the shutter speed (and angle)?"

Shutter speed is the amount of time the shutter is open to expose the sensor / media

Frame rate is the number of frames per second

Shutter angle is the film equivalent to shutter speed and is used by most professional systems.

the longer the shutter is open during the exposure the longer your trails will be

I work in shutter angles, you can find the conversion math on wikipedia

at 24 /25 fps a normal shutter is at 180* (degrees) which is 1/48 or 1/50 of a second. ( shutter is exposing for 1/2 of the frame rate)

for longer trails you should test at 240* 320* or Open
Electronic shutters allow for an "open" setting but more often than not it is not technically full open at 360* but it is not the same look as one would fi

you might also try slower frame rates with a longer opening to the shutter.

Studio37

Post and Production Workflow Consultant
Production and Post Stereographer
Chicago, IL

http://blogs.creativecow.net/24640

 Re: Frame Rate vs Shutter Angle - CONFUSED!on Oct 29, 2012 at 4:24:12 pm

Thanks for the response, that's really helpful.

 Re: Frame Rate vs Shutter Angle - CONFUSED!on Oct 29, 2012 at 5:18:01 pm

Charlie
what you are try to do is beyond the realm of physics at least in this reality.

You can't stop motion and smear the light using shutter speeds or high frame rates. High frame rates only allow for minuscule amounts of time for the shutter to be open, not enough to allow for a trail off the object.

You could use:
a) High Speed Flash (Lighting Strikes or the like) to program a flash to stop the action at a specific point in time and allow the open shutter to smear the light

b) Composite your HS shot with another that has the smear effect you create in post.

Studio37

Post and Production Workflow Consultant
Production and Post Stereographer
Chicago, IL

http://blogs.creativecow.net/24640