Tuesday, July 10, 2012

Fundamentals of Photography - Shutter Speed

Copyright Monica L. Shulman
Focal length 18mm, Aperture f/20, Shutter Speed 1/1600, ISO 640.

This is the second part of my fundamentals of photography series and this time we're focusing on shutter speed.

What is shutter speed?

Shutter speed controls how long the sensor (or the film if you don't shoot digital) is exposed to light.  Basically, if you're shooting a moving object and you use a very fast shutter speed, it will appear to be frozen in time.  But if you use a slow shutter speed, anything that is moving in the image will be blurry.

As a general matter, if you're using a fast shutter speed you want to be sure that you have plenty of light because the faster the shutter speed, the less amount of light that will reach the sensor.

Copyright Monica L. Shulman
Focal length 500mm, Aperture f/10, Shutter Speed 1/400, ISO 800 (I normally wouldn't shoot at such high ISO in broad daylight but I'm guessing that I set it pretty high when I was out shooting the night before and I forgot to change it).

How do you measure shutter speed and how do you set it?

Shutter speed is measured in seconds and micro seconds.  They usually range from 30 second exposures to 1/8000 exposures (eight thousandths of a second aka super duper fast ) for most cameras.  When you choose shutter speed priority you have control over the shutter speed setting and the camera chooses the right aperture and hopefully you get the right exposure.  In shutter speed mode you can adjust the value throughout the entire range that the camera can shoot (ie. 30 seconds to 1/8000 of  second).

Some cameras let you shoot on a Bulb setting which allows you to open the shutter for an arbitrary amount of time and the speed is based solely on how long you hold down the shutter button.  Because of camera shake, shooting in bulb mode is usually done with a tripod and a remote shutter release.

Copyright Monica L. Shulman
Focal length 50mm, Aperture f/1.6, Shutter Speed 1/10 of a second, ISO 400.  
I took this on the street at dusk and my camera was way too slow for the light available.  I think it looks cool and kind of dreamy.

Camera shake and Motion Blur

Speaking of camera shake, your photos will be blurry if your shutter speed is too slow for a given focal length (also if you don't have enough light to shoot with) and if your camera is moving while the shutter is open then you will get a blurry image.  A good rule thumb is that you need to use a shutter speed that is reciprocal to the focal length (how zoomed in you are) you're using.  Like if you are using a 30mm lens on a full frame camera, then you should use a shutter speed that is at least as fast as 1/30 of a second.  The higher your focal length (the more zoomed in you are), the faster the speed that you will need in order to avoid camera shake.  If I'm shooting handheld (not on a tripod) I usually just make sure I have a faster speed than I think I need for the light I have available.  This is especially true if I'm taking pictures of the baby since on top of potential camera shake I've also got the issue of motion blur because of a very fast moving kid.  As a general matter, if your speed is too slow you can usually hear the shutter click and close rather slowly so you'll be able to tell pretty easily before you even look at your photo whether or not it will be blurry. 

And, the rule of thumb goes out the window if you're shooting on a tripod since you can get sharp (even in low light) images with no blur if your camera is stable.  Plus if you're shooting long exposures you'll need that stability.  The other thing that you'll have to be mindful of in these situations though will be the available light (flash or natural) - you want to make sure you have enough so you can avoid images that are too grainy (unless that's what you're going for).  I'll cover this on another post when we go over ISO...stay tuned!

Any questions or tips of your own, please be sure to leave them in the comments!

Don't forget to check out the first part of this series: Fundamentals of Photography - Aperture
Also, in case you missed it, tips for shooting in low light.

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