Home of Professional Cinematography since 1996

Shutter & The CineAlta For Composite Work

Published : 24th October 2003


Doing a green screen shoot with someone running. FX people are wondering if it's better to engage the shutter to let them pull cleaner mattes with no motion blur - they say they can always add that in post.

My experience with shutters in video cameras is a stuttery, strobe-like effect - not particularly pleasing. However is it better to use the shutter in a case like this and at what angle?

Thanks

Steven Wacks



Steven Wacks wrote :

>Doing a green screen shoot with someone running. FX people are >wondering if it's better to engage the shutter to let them pull cleaner >mattes with no motion blu

Depending on the rout they take they are right because they can add interstitial frames off of clean crisp frames to start with.

>However is it better to use the shutter in a case like this and at what >angle?

At 30 P (Actually use 29.97P) Which I would recommend for that type of shot.

OFF is 1/30th, +1 Stop
180° is 1/60th, Baseline exposure
90° is 1/125th, -1 Stop
45° is 1/250th, -2 Stops
22° is 1/500th, -3 Stops

I shot Basketball Players in HD with Dan Schmidt and he was going to do still frame freezes for some VFX thing he was doing.

Jumping and running of humans can be frozen by 1/250th but if you have the light it is better to insure success rather than “hope for it”. Go for 1/500th, the strobier it looks the better.

Remember they will add in between frames if they have crisp edges.

B. Sean Fairburn
Director of Photography
Castaic Ca



>Doing a green screen shoot with someone running. FX people are >wondering if it's better to engage the shutter to let them pull cleaner >mattes with no motion blur - they say they can always add that in post.

Try a test shoot for the effects folks. A mechanical metronome shot with a very short shutter. Hi con lighting against a black background so you can easily see the effects rendered motion blur/integration. The swinging arm generates a reciprocating semicircular arc motion that is different in speed and direction from frame to frame. Try to set it to some speed that is not easily divisible by/into the frame rate. 121 beats/min with a beat being a one way swing of the arm.

Also shoot the same metronome with about 30% of the arc occluded by a sharp, static vertical black foam core foreground edge.

It's an easy tabletop shoot to stress test motion estimation algorithms in compression systems and effects tools.

>My experience with shutters in video cameras is a stuttery, strobe-like >effect not particularly pleasing.

That's the missing 180 degree shutter motion integration in the fast action. Part of the Ultimatte promise and process is the ability to manage the effects of motion integration across the matte color. You should also talk to someone at Ultimatte about this for more detail.

Pete Fasciano
Fellow, Advance Development
Co-founder, Avid technology



Pete Fasciano wrote :

>It's an easy tabletop shoot to stress test motion estimation algorithms in >compression systems and effects tools.

Great tip! I always loved mechanical metronomes...great excuse to get one.

Jeff Kreines



Historically, shutters have been used in sports (30 frame video)to remove the motion blur from slomo replays of fast action. Higher frame rate camera/recorder combinations like the LDK 23/EVS fixed all that. So the answer to capturing any motion faster than walking is NOT slower frame rates like 24 frame. The use of shutter in 30 frame cameras provided a band-aid solution but ALWAYS created that "stuttery, strobe-like, not particularly pleasing effect", especially in cameras using sensors with less than optimal dynamic resolution characteristics (e.g. FIT, IT cameras).

However, if you are shooting 24 frame HD video, you might try shooting your motion sequences at 30 frame with some shutter, and even though it will still produce that stuttery look, it will look much better than 24 frame with shutter.

GEORGE C. PALMER
HDPIX, INC.
HD and Digital Imaging Services
www.hdpix.com