Shutter Speeds

R

Ricpolitics

Member
I have a pretty good idea about shutter speeds, but I still feel like I can't grasp the idea totally. What is considered a REALLY fast shutter, as opposed to a slower shutter speed. And what would each speed be more necessary to shoot with? Basically, what's the simplest way to define "shutter speed".
 
They way i understand fast is higher speeds 1/1000 or 1/500
I guess due to the fact that images are "faster" less blur
Slower is the opposite, slow blurry images..
1/20 or so
 
The shutter speed is the amount of time that the CCDs are read per frame (or per field, in 60i). 1/60 = being read for 1/60th of a second.
 
The shutter speed describes the length of time that light is sample for a frame. For example, in 24 fps the normal shutter speed is 1/48th of a second. There are two main consequences of changing shutter speed; it changes the representation of motion and it changes the exposure.

Faster shutter speeds sample the light for a shorter period of time, so objects have to be moving faster to exhibit motion blur. But faster shutter speed also means there is less total light being used in the sample, so to get a proper exposure, you have to open the iris more.

Slower shutter speeds sample the light for a longer period of time, so objects exhibit more motion blur, and there is more total light in the sample. To get a proper exposure, you have to close the iris more.

Opening and closing the iris changes the depth of focus in the image. So there is lultimately a trade-off between motion blur and depth blur. Slower shutter -> more motion blur -> more light -> close iris more -> less depth blur (deeper focus). And Faster shutter -> less motion blur -> less light -> open iris more -> more depth blur (shallower focus).

When you know these trade-offs you can change the shutter speed to get different motion blur or depth blur effects, or you can use the different shutter speed to get more exposure options.

Here are examples of different shutter speeds at 24 frames per second.

DVX_shutter_speed.jpg


And here is a detail showing the difference in sharpness:

shutter.jpg


These images show the camera being panned at about the same speed. The iris was adjusted to get about the same exposure for each shutter speed.

Hope that helps.
 
Andy,

Thank you for the excellent tutorial.

When I started shooting video at my church, I was overwhelmed with the Canon XL2. We purchased an instructional DVD called "Camera Command" and it really helped me get up to speed with camera operation. I've since purchased my own DVX100B (got the video bug now) and am so much less intimidated since I've watched the DVD about a dozen times!

The guys in the video use humor when explaining the concepts which is nice since some instructional videos can be kind of dry.

If anyone is interested, check out: http://www.cameracommand.com/.


Marty
 
Great post Andy - would like to make a slight suggestion however.

To get a proper exposure, you have to close the iris more.
Click to expand...

In a normal inlit scene true. In a lit scene I would rather keep my iris less closed than say 6.8 and drop my light levels down or even for that matter apply the ND filter to do the same.
 
Thanks ncje. Good points. I should have said "one way" to adjust the exposure.

So... if there is too much light, you can a) close down the iris, b) increase the shutter speed, c) use the ND filter in the camera to cut the light, d) add ND filters in front of the camera, or e) reduce the light in the environment. (Or some combination of these).

And... if there is too little light, you can a) open up the iris, b) decrease the shutter speed, c) use the GAIN to amplify the signal, d) add light in the environment. (Or some combination of these).

Coincidental changes that result from exposure decisions:
  • Iris -> changes focus depth
  • Shutter -> changes motion blur
  • Gain -> amplifies noise as well as signal
 
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LOL at Andy ... the most comprehensiive posts you can find. You want info ... erm see Andy.

P.S. the reason I say to keeep 6.8 is to retain focus. Want a beer? Im drunk :P
 
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