DEPTH OF FIELD: Understanding Photography in a Simple Way
What is the depth of field in photography?
Depth of field or (DoF) is not rocket science in photography, a straightforward concept. It merely refers to the range of distance that appears acceptably sharp within an image. Ultimately, it will determine how focused your subject appears when taking shots.
Additionally, this distance depends on the camera type you are using, focusing length and aperture (f-stop). Again, viewing distance and print size always affect our perception of DoF. On the positive side, the depth of the field occurs in a gradual transition. For example, it does not deliver an abrupt change from sharp to blurry but instead does it gradually. That is why when you focus your camera; all scenes in front and or back of the focusing distance loosen sharpness.
CIRCLE OF CONFUSION
Circle of confusion (CoC) is a concept in photography that has some importance. Understanding the circle of uncertainty will help you achieve sharp images in your photography work. For instance, you have heard professional photographers saying, “it’s tack sharp” or “that’s a sharp photo.”
What is that!
Generally, because we don’t have a common point of transition, the term circle of the confusion comes in place to define the depth of the field. In a nutshell, it refers to how much the point is to be blurred so that you no longer perceived its sharp. So, this measurement of a point of light that falls on the camera sensor is known as a circle of confusion. When the circle of confusion is blurry enough to the photographer’s eyes, that region is known as outside the depth of field. A photographer will see it as not sharp anymore.
Diagram illustrating the circle of confusion
In our diagram above, to illustrates the circle of confusion, the left side stands for light from your subject. On the other hand, we have the right side, which stands for the image created by light. Additionally, the red lines stand for the view from the subject. The purple and green dots stand for the closest and farthest distance of allowable sharpness.
Furthermore, a point light source will manifest in various degrees of blur when your camera records it. Here, the segment with larger dots that is blurry is no longer acceptable since it’s not sharp. It is what defines the circle of confusion. In the diagram illustration, circles are significant for the sake of demonstration compared to what happened in reality. Usually, a circle of confusion occupies a tiny of your camera sensor’s area.
So, how do you know that circle of confusion is perceptible to your eyes.
In particular, an acceptable circle of confusion is one that passes when you enlarge to a standard 8×10 inch print. Again, it will go unnoticed when you observe it from a standard viewing distance, which is 1 foot. Notably, manufacturers do assume that a CoC is negligible if it’s no more substantial than 0.01 inches at this viewing distance and print size. In this case, if you blurred by more than 0.01 inches, then anything will appear blurry. It is the standard that camera manufacturers use to provide lens DoF markers.
CONTROLLING DEPTH OF FIELD
The print size and viewing distance influence how large the circle of confusion appears to your eyes. However, we also have two other main factors that determine how big the circle of confusion will appear on your camera sensor. They include:
- Focusing distance
For instance, a larger aperture –smaller f-stop number and closer focusing distance deliver a shallower depth of field. A good example is when you use an aperture of f/2.8 to create a photo. Here, your shot will produce images with the least depth of field. It is noted that your image will have a background with the most blurred relative to the foreground. Likewise, an f/5.6 and f/8.0 will deliver a progressively sharper background.
In summary, factors that influence depth of field in your image are:
- Subject magnification
- Camera’s image sensor size
Let nobody cheats you that lens focal length will influence DoF. Many photographers always wonder why they can’t use the smallest aperture to produce the best depth of field. Usually, a small aperture softens the images you take. Here, an effect known as diffraction becomes a more restrictive factor than the depth of field as the aperture becomes smaller. Surprisingly, this is the reason why pinhole camera has low resolution despite their extreme depth of field.