Aperture refers to the opening of a lens's diaphragm through which light passes. It is calibrated in f/stops and is generally written as numbers such as 1.4, 2, 2.8, 4, 5.6, 8, 11 and 16. The lower f/stops give more exposure because they represent the larger apertures, while the higher f/stops give less exposure because they represent smaller apertures.
How Aperture Affects Depth of Field Depth of field is defined as "the zone of acceptable sharpness in front of and behind the subject on which the lens is focused." Simply put: how sharp or blurry is the area behind your subject. Here's the equation: The lower the f/stop—the larger the opening in the lens—the less depth of field—the blurrier the background. The higher the f/stop—the smaller the opening in the lens—the greater the depth of field—the sharper the background.
How Aperture Affects Shutter Speed The f/stop also affects shutter speed. Using a low f/stop means more light is entering the lens and therefore the shutter doesn't need to stay open as long to make a correct exposure which translates into a faster shutter speed. Again, the reverse is true: using a high f/stop means that less light is entering the lens and therefore the shutter will need to stay open a little longer which translates into a slower shutter speed.
Aperture comparison assignment
Compare the following aperture sizes and how they affect depth of field in your pictures *we are focusing on depth of field as aperture speed also effects exposure f3.5 f5.0 f7.1 f10.0 f18.0
Look for a subject with a lot pattern or repetition
keyboard
books on a shelf
bumpy block wall
cars in a row
tape measure
font on a book page
plaques on a wall
etc
Then take photos at the aperture sizes above to compare how depth of field is affected in these photos
Create a Photoshop file to compare your pictures:
File > New
Set up your canvas to 6" tall x 24" wide
Crop your Photos to a 4" x 4" size (300 Resolution)
Copy them to the New Canvas
Leave a 1" margin on all 4 sides and .5" between photos
Add text under each photo to label the aperture sizes
Text tool is a capital T symbol on the left side of the screen
Be sure your font is large enough to read easily
Turn in when done
*Note the bottom example is circled just to show how depth of field changes - DO NOT put circles in your photo