What Does an Aperture Control in Video

About Lens Aperture

The aperture of a lens is one of the primary features of a lens. It is significant because it is one of the lens features that determine the quality of an image. The lens Aperture is denoted with “f” followed by a number. For example, f1.2 which can also be written as f/1.2. 

While the bigger f-number should normally indicate a larger aperture, the reverse is correct in this case. Smaller f-numbers indicate wider openings. This means that the smaller the f-number, the larger the aperture, and vice versa. 

Although the aperture is a lens feature, it works hand in hand with the camera shutter(1). It’s important to note that no lens aperture width is bad or good, good images are basically a function of the right aperture for the right lighting scenario. Since wider apertures let in more light, it’s natural that the shutter speed is fast to match, so as not to over expose the camera sensor. The reverse applies to small apertures, the shutter speed is slowed to match. 

So, what does aperture control? 

While the aperture controls the amount of light that the lens lets into the camera, the shutter controls the length of time the light gets to the sensor. These processes are mostly automated on digital cameras. 

“The aperture of a lens works closely with the shutter speed so as to avoid over exposure or under exposure of light to the camera sensor.”

The major image feature the aperture controls is the image depth of field(2). An image’s depth of field basically refers to the area of an image in focus. It is the ratio of the part of an image in focus to the part of the same image out of focus. An image’s depth of field can either be deep or shallow. It is shallow when only a small area of the image is in focus while it is deep when a larger area of the image is in focus. 

Relationship Between Aperture and Depth of Field 

It has already been noted that aperture affects the depth of field in images. But what does low aperture or high aperture mean to an image’s depth of field? 

A higher aperture, represented by a descending f-number, causes a shallower depth of field in the image. This means that the larger the lens aperture, the smaller the area of the image frame in focus. Basically higher aperture means shallow depth of field. 

On the other hand, a lower aperture, represented by an ascending f-number, results in a deeper image field depth. In simple terms, low apertures means a larger area of an image frame will be in focus. 

To further explain, an f/2 aperture will have less of the image in focus than an f/22 aperture although the f/2 aperture lets in more light. 

High and Low Apertures in Videography 

In videography, high or low apertures have their best use cases. Generally, high apertures create better images compared to low apertures if the lighting parameters are constant and the shutter speed is adjusted accordingly.

However, videographers can’t ignore the depth of field associated with the different apertures. So, high apertures are employed when the videographer wants a little of the image in focus, it is usually used to single out a character during filming or wildlife documentary. On the flip side, low apertures are employed when the videographer needs to get more subjects in focus, for example, when filming a fight scene or when engaging in sports videography.