How shutter speed affects picture?

L

Lor

Well-known member
I was watching a workshop by Robert Kositchek, USC School of Cinematic Arts and he mentioned about slow shutter speed controlling motion. My understanding is that if I decrease the shutter speed I will get more motion blurr, correct? But he said, the image will look much sharper. So my question is, how much sharper? Why is it sharper since shutter speed only controls motion? Does it also indirectly controlling picture quality too?

I have the Sony PMW-EX1 camera. I usually shoot at 1080p/24 with 1/48 shutter speed. To create some of the sharpest image with minimal blurriness, what shutter speed should I use? I know that the subject and camera should not be moving to reduce motion blurr with lower shutter speed but I like to know what speed is more appropriate.
 
Either he slipped up or you heard wrong. My peanuts are on you.

Slowing shutter speed increases the chance of motion blur, because the frame of film is being exposed for a longer period.

Reducing shutter angle sounds like the same thing, but is actually the opposite. When the actual shutter angle is decreased (in degrees), the shutter speed is effectively 'faster'.

Therefore if someone is talking about decreasing the shutter, without saying 'speed', they are probably referring to the angle... Especially in film. If this guy works in film, then he is talking in degrees. This is because you actually take a special wrench, move the reflex mirror aside, and change the shutter angle.

The whole concept of adjusting the shutter as fractions of a second and 'slowing' it has become common jargon thanks to the wonderful world of video and digital cameras, although film people do know what angle = which fraction.


EDIT: Watching the video, he said 'small shutter' for sharp images. This meant small shutter angle, not shutter speed.

my 2cents
-ryan
 
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Lor,

1/48th is the equivalent shutter speed to a 180 shutter angle on a film camera, which allows 50% of the shutter disc to pass light to the film plane. It's very much like a pie chart, with 180 degrees missing.

What Robert meant when he said a slower shutter speed makes things crisper, is in reference to a film camera, where a lower number means a smaller shutter angle, therefore allowing less light per second and decreasing motion blur. Doing this intensifies movement, and can make things seems faster, but doesn't decrease the speed in which the shutter passes the gate.

When we get into the digital realm, it's easy to see where one may get confused. Because we use fractions instead of degrees of a whole, a slower shutter does actually mean a slower shutter, things will have more motion blur and can streak if the camera is moved when the shutter is 1/24th or lower.

On film, low shutter angles like 45 degrees and 90 degrees are used in war films, action sequences, chase sequences, etc. If you watch Saving Private Ryan, the opening scene is a great example of 45 degree shutter. This can be matched in the digital realm by shooting 1/120th (90 degrees) or 1/250th (45 degrees).

The standard shutter angle is 180 degrees (1/48th), and is used more than any other. Most situations call for a standard angle, but when you want to provide a specific effect, that is when changing the shutter will come into play. Hope this answers all your questions, happy shooting!
 
Many thanks for all your responses. Got it. By the way, I thought I saw someone post a formula for converting shutter speed for shutter angle somewhere. I don't quite remember where. I'll be nice though.
 
From Wiki :)

In cinematography, shutter speed is a function of the frame rate and shutter angle. Most motion picture film cameras use a rotating shutter with a shutter angle of 165° or 180°, which leaves the film exposed for about 1/48 or 1/50 second at a standard 24 frame/s.[5]
Where E = Exposure, F = Frames per second, and S = Shutter angle:[5]
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Click to expand...

If that's not what you meant check here:
http://www.freshdv.com/2007/07/shutter-speed-vs-shutter-angle.html
 
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