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Sony NXCAM NEX-FS700 CineAlta
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Old May 10th, 2013, 04:29 AM   #1
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Increasing shutter speed for fast action

I'm aware of the 180 degree rule when shooting (so aim to get a shutter speed as close to 1/480 when shooting at 240fps) but should I aim to use a higher multiple when shooting very fast action to avoid motion blur, e.g. 1/960?
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Old May 10th, 2013, 01:39 PM   #2
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Re: Increasing shutter speed for fast action

If you're shooting at 240 frames you don't have to worry about motion blur if you follow the 180 rule. It's smooth as butter.
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Old May 10th, 2013, 02:01 PM   #3
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Re: Increasing shutter speed for fast action

what james said. a fraction is a fraction no matter the frame rate, anything above 100 has pretty little blur for non quick moves, and anything above 200 should be crispy. only if you're shooting really fast action would you want to dial it up a bit more.
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Old May 10th, 2013, 07:57 PM   #4
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Re: Increasing shutter speed for fast action

If things are still moving fast in frame when shooting at 240fps then it may be worth making the shutter even faster. It all depends on the speed of motion in frame AFTER it's been slowed down. Haven't tried it specifically, but my guess is that 180 degree shutter should be fine for carbonation at 240fps, but you might want to go down to 90 degrees or 45 degrees if shooting glass shattering.
Just remember that closing down the shutter can mean adding a LOT more light!
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Old May 12th, 2013, 10:22 AM   #5
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Re: Increasing shutter speed for fast action

I agree with Dave... it is now easy to add motion blur in post, but we don't have any tools that I am aware of that will remove it
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Old May 12th, 2013, 01:14 PM   #6
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Re: Increasing shutter speed for fast action

From my experiences with this camera, you don't need to worry about motion blur when you're at 240fps if you're ss is correct. On mine, the closest ss is 500 since it doesn't go to 480. There might be a way to fix that in the settings but I haven't had the need to. I've shot skateboarders close up doing tricks, water guns, water balloons hitting someone in the face, my dog running 40 mph. I've never had any motion blur issues. If you crank your ss higher than that it becomes overkill, not to mention you lose valuable light... and when you're shooting that high frames with this camera light becomes the most important thing.
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Old May 15th, 2013, 09:47 AM   #7
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Re: Increasing shutter speed for fast action

Here is a question for those with high frame rate cameras...
If you are shooting propeller aircraft, and you are shooting at a high frame rate, can you still obtain a full prop arc by using a higher shutter speed?
Or does the increased shutter speed produce a stopped prop image?
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Old May 15th, 2013, 10:04 AM   #8
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Re: Increasing shutter speed for fast action

what exactly do you mean by full prop arc? Props spin at 2500rpm, so around 42 rotations per second, if your camera shoots 240 frames per second, about 6 frames per rotation, which is not very slow, since we percive slow as starting about 60fps for normal actions, i imagine you'd want 60 frames per rotation, or about 2500fps. that's for how slow it would look, as for the amount of blur.... idunno, i'm terrible at math
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Old May 16th, 2013, 08:38 PM   #9
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Re: Increasing shutter speed for fast action

A better term to have used would have been prop disk. The shutter speed is sufficiently slow that the moving propeller is visible as a translucent disk.

Prop arc is what one sees when the shutter speed is just fast enough to capture the prop moving through 30-45 degrees of arc, leaving a blur but not a stopped prop where you can see the individual blades.
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Old May 17th, 2013, 09:29 AM   #10
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Re: Increasing shutter speed for fast action

Doing the quick (approximated) math:

If we go on the assumption that it's making 42 rotations/second

42 x 360 degrees = 15,120 degrees traveled per second

Let's now say that the camera is set for 180 degree shutter at 240 fps, then each exposure is 1/480 of a second

15120 / 480 = 31.5 degrees traveled during exposure time of one frame

Hence the 'prop arc' effect to which you are referring, where the prop is traveling ~1/12 of a rotation during a single frame exposure.

(If shutter is not engaged and the exposure is 1/240 of a second, then that travel becomes 63 degrees, or approx 1/6 of a rotation).
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Old May 17th, 2013, 09:42 AM   #11
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Re: Increasing shutter speed for fast action

Quote:
Originally Posted by Tim Davison View Post
I'm aware of the 180 degree rule when shooting (so aim to get a shutter speed as close to 1/480 when shooting at 240fps) but should I aim to use a higher multiple when shooting very fast action to avoid motion blur, e.g. 1/960?
The "180 degree shutter rule" applies mostly to low frame rates in the 24-30 fps range. The purpose is to insure that you get some blurring in the individual film frames so that when you view the motion picture, this motion blur is sufficient that your visual system interprets it as smooth motion.

As your frame rate increases, your minimum shutter speed also increases. At 240 fps, you more or less have to shoot with a shutter speed of 1/240 sec or higher. If you've looked at stills made at 1/250, you see very little motion blur even when the subject is high speed sports.

What I'm sayin' is that the higher the fps, the less the "180 degree shutter rule" applies. In fact, you can probably get away with a 360 degree shutter for most everything at such high frame rates. Which will conserve your lighting or at least keep you out of high gain (and therefore high noise / low gamut) situations.

No need to take my word for it either -- run your own tests, make your own decisions based on your own results.
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