Exposure: Aperture/Depth of Field

What is Aperture?

Simply put, aperture is a hole within a lens, through which light travels into the camera body. It is easier to understand the concept if you just think about our eyes. Every camera that we know of today is designed like human eyes. The cornea in our eyes is like the front element of a lens – it gathers all external light, then bends it and passes it to the iris. Depending on the amount of light, the iris can either expand or shrink, controlling the size of the pupil, which is a hole that lets the light pass further into the eye. The pupil is essentially what we refer to as aperture in photography. The amount of light that enters the retina (which works just like the camera sensor), is limited to the size of the pupil – the larger the pupil, the more light enters the retina.


So, the easiest way to remember aperture, is by associating it with your pupil. Large pupil size equals large aperture, while small pupil size equals small aperture.  (source)

image courtesy boogy man

Size of Aperture – Large vs Small Aperture

In photography, aperture is expressed in f-numbers (for example f/5.6). These f-numbers that are known as “f-stops” are a way of describing the size of the aperture, or how open or closed the aperture is. A smaller f-stop means a larger aperture, while a larger f-stop means a smaller aperture. Most people find this awkward, since we are used to having larger numbers represent larger values, but not in this case. For example, f/1.4 is larger than f/2.0 and much larger than f/8.0.

Take a look at this chart (image courtesy of Wikipedia):

The size of the circle represents the size of the lens aperture – the larger the f-number, the smaller the aperture.

What is Depth of Field?

One important thing to remember here, the size of the aperture has a direct impact on the depth of field, which is the area of the image that appears sharp. A large f-number such as f/32, (which means a smaller aperture) will bring all foreground and background objects in focus, while a small f-number such as f/1.4 will isolate the foreground from the background by making the foreground objects sharp and the background blurry. (source)

TO DO:


Click These links: 

1. PhotoAxe-Depth of Field  

2. PhotoAxe-Aperture  

3.  ShortCourses-Aperture-- Click on ALL red animation buttons on the left side of page!! 
4. http://ruleofthirdsphotography.com/interactive-aperture/
5. Exposure Controls
6.Choosing Exposure Modes (focus on Av, A-DEP, and Close-Up (Flower Icon))
7.  NGA PhotoSnapper <----fun font="">

Exposure: Shutter Speed

What is Shutter Speed?

Shutter speed, also known as “exposure time”, stands for the length of time a camera shutter is open to expose light into the camera sensor. If the shutter speed is fast, it can help to freeze action completely, as seen in the above photo of the dolphin. If the shutter speed is slow, it can create an effect called “motion blur”, where moving objects appear blurred along the direction of the motion. This effect is used quite a bit in advertisements of cars and motorbikes, where a sense of speed and motion is communicated to the viewer by intentionally blurring the moving wheels.

How shutter speed is measured

Shutter speeds are typically measured in fractions of a second, when they are under a second. For example 1/4 means a quarter of a second, while 1/250 means one two-hundred-and-fiftieth of a second or four milliseconds. Most modern DSLRs can handle shutter speeds of up to 1/4000th of a second, while some can handle much higher speeds of 1/8000th of a second and faster. The longest shutter speed on most DSLRs is typically 30 seconds (without using external remote triggers).

Fast, slow and long shutter speeds

Fast shutter speed is typically whatever it takes to freeze action. For me, it is typically above 1/500th of a second for general photography and above 1/1000th of a second for bird photography.

Slow shutter speed is considered to be the slowest shutter speed that you can handle without introducing camera shake. 

How about long shutter speed? Long shutter speeds are typically above 1 second, when you have to use a tripod to get acceptably sharp images (for low-light/night photography or to capture movement).

How to set shutter speed (if you have a DSLR camera)

Most cameras handle shutter speeds automatically through in-camera metering. When the camera is set to “Auto” mode, both shutter speed and aperture are automatically selected by the camera. 

There are two ways to manually set the shutter speed:

a) By setting the camera to “Shutter Priority” mode, where you set the shutter speed and the camera automatically selects the aperture.

b) By setting the camera to “Manual” mode, where you set both shutter speed and aperture manually.

c.)  By setting the camera to "Bulb" or B mode.   This mode allows the user to hold in the shutter-release button  in and the shutter will remain open the entire time while the button is being held. 

How to set shutter speed (if you have a regular point & shoot camera)

Most cameras handle shutter speeds automatically through in-camera metering. When the camera is set to “Auto” mode, both shutter speed and aperture are automatically selected by the camera. 

However, we can "trick" the camera into providing us with a short or a long shutter speed.  It will be trial & error, so be prepared to take a lot of photos and check them to see if the moving object looks blurry.

 Most digital cameras have at least one setting that will provide a long shutter speed.   First, try setting your camera to "Landscape" mode (Mountain Icon) .  This will make moving objects look blurry in medium to dim light locations.   You can also try shooting in "Night" mode or "Night Portrait"  (You will probably have to turn OFF the flash)  You can also try "Fireworks," but this setting has a very long shutter speed and should be used in dark locations.

Click all of these links and take notes on what is important.  You'll be given a quiz on this later!


ShortCourses-- Click on ALL red animation buttons on the left side of page!!

• Shutter-Controls Light and Motion 
• Using Aperture and Shutter Speed Together

• Understanding Exposure  <--try this one out!

• Photo Op Interactive  <---this is fun.  Be sure to try this out if you haven't done it yet!