How to Use the Camera's Aperture to Change Depth of Field

Photography exposures are controlled by three main functions. ISO or film speed, shutter speed and aperture control the amount of light to produce a properly exposed image. ISO has an impact on the resolution of the image. Shutter speed impacts the ability to freeze motion. Aperture controls the depth of field or depth of focus. Modern digital cameras have automatic modes that set all three based on the amount of light. Many digital cameras allow you to set the aperture manually and compensate for exposure by automatically compensating the shutter speed and ISO.

Difficulty: Easy

Instructions

Things You'll Need:

• A Digital Camera that allows you to select manual adjustments
• An analog camera and film

1. 
   Image at f16

   This photograph of a rosemary plant was taken in full automatic mode on a Nikon D50. Notice the rocks and trees in the background. They are sharp and clear. That sharpness actually distracts from the image of the rosemary plant on the balcony. The leaves of the rosemary plant actually blend a little with the trees behind it. It causes some visual confusion of the subject rosemary plant.

2. 
   Image at ff11

   The Nikon D50 was set to APERTURE MODE which allowed us to adjust the f stop manually. The aperture is actually an iris. The bigger the opening the smaller the f stop number. An aperture of f16 is a smaller opening than f11. Notice the rocks in the background. They are not as sharp.

3. 
   Image at f9

   This image was taken at f9. Notice the rocks now. They are less sharp, the depth of field has been reduced. You need to be careful to not go too far. We still want to have the entire rosemary plant be in focus.

4. 
   Image at f5

   Notice the rocks now. There can now be no doubt that this is a picture of a rosemary plant.

Tips & Warnings

• Reducing depth of field is very helpful in reducing unwanted distractions in the background of an image.
• The closer you are to an image the more reduced the depth of field.
• Usually select a smaller aperture (higher number) for scenes and panoramas
• When doing portraits at an angle select the aperture carefully. You want to make sure the entire person is in focus.

Resources

• Nikon