A camera acts similarly to a human eye. As images are captured and transferred into digital images or film, so are images processed and converted into pictures inside the brain. As a camera shutter adjusts to let in more or less light, so does the iris. One of the most fascinating aspects of the human eye is its ability to focus on one part of a scene and block out distractions. By adjusting the focal plane and depth of field on a camera, a photographer can create a similar selective-focusing effect.
The focal plane is the distance between your camera lens and the perfect point of focus in an image. This area is located a certain distance in front of your camera lens, and spans horizontally, left to right across your frame.
FOCAL PLANE X DEPTH OF FIELD
Despite what the name suggests, the focal plane, or the sharpest plane of focus in an image is not the only part of an image that actually appears to be in focus. Although the points adjacent to the focal plane are not in perfect focus, the brain registers them as being in focus if they lie within a certain range.
The area around the plane of focus that appears to be in focus is called the depth of field. You can adjust the depth of field to be deeper (more of the image appears in focus) or shallower (less of the image appears in focus) by adjusting your aperture (f-stop), the part of the camera that controls light entry.
Here’s a quick guide on how you can deepen and reduce the depth of field:
- Deep depth of field = Large f-stop (small aperture) + slow shutter speed
- Shallow depth of field = Small f-stop (large aperture) + fast shutter speed
Focal Plane x Distance
Aperture and distance are the two biggest factors in focal plane and depth of field; the distance between the camera and the subject, and the distance between the subject and their background and foreground.
- Distance between the subject and the camera: Make your depth of field shallower by moving the camera closer to the focal plane. Make it deeper by moving the camera farther from the focal plane. Moving closer to a subject is a great technique for taking images with soft backgrounds using a limited lens.
- Distance between the subject and the background: Create a shallow depth of field effect by moving the subject farther away from their background. This will create an image that shows a crisp hyper-focused subject standing in front of a blurred background. Bring more background into focus by moving your subject (plane of focus) closer to the background
Why Does The Focal Plane Matter?
Portrait photographers can use focal plane and narrow depth of field to draw attention to the freckles on their subject’s face by positioning the subject with their freckles in the focal plane, and positioning them at a distance from their background for a dramatic background blurring effect. A landscape photographer can use focal plane and a deep depth of field to showcase a mountain range, expanding the area of focus to display its strong ridgelines and grandeur.
Just like a human eye focuses and refocuses on points of interest, the focal plane directs the attention of the viewer to the parts of the image that are most important, and helps blur out any background or foreground distractions. Regardless of your style of photography, understanding the focal plane and depth of field will only elevate your photographic capabilities. Inability to control focal plane can result in chaotic, busy images, but a well-designed focal plane can help you tell the story you wish to tell, and can make the viewer feel like they are really there.
For more on focal plane and depth of field, read our previous article, Understanding Depth of Field.