Photography: 3 - Shutter Speeds

Lenses are come in different sizes:

<30mm = wide angle50mm = what the human eye sees>70mm = TelephotoZoom = Combines all three into one

24mm 50mm 70mm

DOF refers to how much of a photo is in focus:

The smaller the f-number,the smaller the DOF:

In your camera – between the lens and the film/CCD - is the shutter

Video on next slide…

http://www.youtube.com/watch?v=lw6doYnO4ng

Think of it as a door that opens for a split second to allow the image of your subject to burn onto the film/CCD…

As the photographer you have control over how long this ‘door’ is open

Typically this will range from 1/1000th of a second (very, very fast) to 1 or 2 seconds (very slow)

The longer the shutter is open, the more chance there is that something in your subject will move, for instance…

…the train appears still

But at a slower shutter speed the train has travelled an inch or so while the shutter was open…

…so the train blurs

And at a very slow speed the train moves so much that it barely registers on the photo…

…and becomes ghost-like

Notice the blurred horses’ legs

Faked with Motion Camera – Android phone app

Not true motion blurLo Res images (480x320)

Notice the sharpness of the legs

If you use a shutter speed slower than 1/60th of a second your photos will suffer from camera shake (your hands can’t hold a camera that still for that long!):

Slow

Fast

…or in old money…

For slow speedsyou’ll need a tripod:

…or wedge your camera against something solid:

Fast Shutter Speed

Slow Shutter Speed

Either:

Set your camera to Shutter Priority mode and take a series of photos of the same moving subject at different shutter speeds

Or, if your camera does not have Shutter Priority, go to www.camerasim.com and experiment with the shutter speed slider

A Quick Overview

Opening the shutter exposes the film/CCD to light

Too little light causes under-exposure, too much causes over-exposure:

You’ll remember that Aperture gives us Depth of Field by changing the size of an iris in the lens:

Think of the iris as a curtain that you can open or close

By opening or closing the iris you control the amount of light getting through it – just like closing a curtain to block out the sun on a bright day

This can be used to compensate for under or over exposure, so the iris can be opened (perhaps to f2.8) to let in more light when using a fast shutter speed, or the iris can be closed (f16) to let in less light with a slow shutter speed…

Fast Shutter / Wide Aperture (f2.8) Slow Shutter / Narrow Aperture (f16)

This is the tricky part of photography to get your head around

We’ll keep coming back to it over the next few weeks

>>>END<<<