Understanding Lens Aperture For Beginners

Rather you want to take up videography yourself, or just understand the process better to communicate with a professional videographer or video team you’re hiring, there’s some basic concepts to understand. The first is Aperture.

What is Aperture?

Aperture refers to the size of the opening in your lens through which light passes to reach the camera sensor. It is typically measured in f-stops, such as f/1.8, f/5.6, or f/22. In video specific lenses it may also be measured in t-stops, which are exactly like f-stops, but measure the exact amount of light that hits the sensor. f-stops are a close approximation of the light hitting the sensor. But for the purposes of understanding the basics of aperture, both f and t-stops function the same. The f-stop or t-stop number indicates the size of the aperture opening: a smaller f-stop number means a larger aperture, and a larger f-stop number means a smaller aperture.

How Aperture Affects Exposure

The aperture plays a significant role in determining the exposure of your video. A larger aperture (smaller f-stop number) allows more light to enter the lens, making the scene brighter. Conversely, a smaller aperture (larger f-stop number) lets in less light, resulting in a darker image. This is why adjusting the aperture is essential for achieving the correct exposure, especially in varying lighting conditions.

Depth of Field and Aperture

Depth of field (DoF) refers to the range of distance within which objects appear sharp in your video. I will do a future video going into more detail about depth of field, but for the sake of this article, just think of it like this: the smaller the f-stop number, the less of your image will be in focus:

  • Large Aperture (Small f-stop Number): A large aperture creates a shallow depth of field, where the subject is in sharp focus while the background is blurred. This is often used in portrait or bokeh effects to make the subject stand out.

  • Small Aperture (Large f-stop Number): A small aperture creates a deep depth of field, where both the subject and the background are in sharp focus. This is useful for landscape or architectural videography, where you want everything in the frame to be sharp.

Depending what is being filmed, having more or less in focus may be desirable. 

Lens Character

Lenses don’t all function the same at different apertures. It’s very common for lenses at low apertures (f1.4 or t1.5 for example) to create an image that is less sharp and can display defects or characteristics that shape the look of an image. These may or may not be desirable depending on the look or style of a project. Wedding videographers might desire a dreamy sort of look with a less clinically sharp lens to make the footage feel more magical. Commerical videographers will likely want to push for a cleaner look. These rules are not hard and fast, but something to be discussed and decided on a project by project basis.

 

Hopefully this article helped give you a basic grasp on what lens aperture is, and how it can affect the look of your image. It’s always important to discuss the type of aesthetic you want on a project with your video team, so they can better select the appropriate lenses, lens settings, and camera equipment for the job to ensure you get the best possible final product.