Depth of field is often talked about as one of the fundamental concepts in the capture of images. A photographer or application will carefully select the depth of field in any composition in order to sufficiently capture their intended perspective.
In simple terms, depth of field refers to the area of a photograph that is in focus. But this definition leaves out a lot of useful information that helps to contextualize the importance of depth of field.
What is Shallow Depth of Field vs Deep Depth of Field?
To understand depth of field, let’s take a quick look at shallow versus deep depth of field. These components will help to understand the variations in focus.
A shallow depth of field refers to an image with a narrower focus. On the other hand, a deep depth of field renders both foreground and background images with sharp resolution. We’ll get into this more later.
First, let’s explore a more profound definition of depth of field.
What is Depth of Field?
So, what is a depth of field, and how does it apply to lenses?
A more detailed definition for depth of field is the full distance between the nearest and furthest points in an object that is in focus. Lenses, like the human eye, are only capable of capturing and focusing so much light. This means certain points will appear sharper than others in photography and other applications.
But adjustments can be made to the depth of field to allow for a wider, or narrower, focus for their shot. There are a few ways to control depth of field by changing or manipulating a lens. They are aperture, focal length, and focusing distance.
Aperture is the hole or opening that light passes through in photography. Aperture is traditionally measured by F-number. A smaller F-number means a wider opening for light, whereas a larger F-number has a more narrow opening. Larger aperture allows, then, allows for more light to pass through. This can result in brighter images, but also reduces the lens’ ability to focus on certain spaces or objects. Likewise, a smaller aperture admits less light, but can result in a sharper image.
A concept related to aperture is what’s known as the Circle of Confusion. In photography, this refers to a point of light that does not come into perfect focus in the image.
In other words, the circle of confusion is the smallest possible point of light that remains blurry in a photograph. Lenses are not capable of achieving perfect image sharpness. So even with a narrow aperture, highly focused images will have blurry spots if you zoom in far enough.
Deep Depth of Field vs Shallow: How this Affects Images
As you might guess, a shallow depth of field has a wider Circle of Confusion than a deep depth of field. That is, the shallower your focus, the more blurred spots of light your lens will produce. A deep depth of field will appear less blurry at normal resolution. But as you zoom in, details become harder to render.
To provide a general example, portrait photos tend to use a shallow depth of field to put more focus on the subject. Landscape photos prefer a deep depth of field in order to capture as much detail as possible.
This is not a problem, of course. It’s simply a natural product of how lenses and light polarization work. But when it comes to understanding the dynamic uses of custom lenses, it is important to understand certain key factors.
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