Photography 101 – What Does the f-stop on a Lens Mean?
Welcome to Photography 101! Today, we’re breaking down the f-stop on a lens—one of the most important concepts in photography. The f-stop, or aperture, controls how much light enters your camera, impacting your exposure and depth of field. Whether you want a beautifully blurred background or sharp focus throughout, understanding f-stops is key. In this video, we’ll explain what it means, how it works, and how to use it creatively in your photography. Let’s begin!
This video is from our Photography for Beginners Course.
Video Summary
This video breaks down the essential relationship between DSLR lenses and aperture, explaining why some lenses are “faster” (and more expensive) than others.
Key Timestamps
- 0:00 – Understanding Lens Naming Learn the standard naming convention: lenses are identified first by their focal length (e.g., 80-200mm) and second by their minimum f-stop (e.g., f/2.8).
- 1:11 – Zoom vs. Prime Lenses A quick distinction between Zoom lenses (variable focal length) and Prime lenses (fixed focal length). Prime lenses often allow for wider apertures since they lack complex zoom glass.
- 2:33 – The “Kit Lens” Variable Aperture Most beginners start with an 18-55mm f/3.5-5.6 lens. This section explains why the minimum aperture changes as you zoom in.
- 4:48 – The Beauty of Prime Lenses A look at the 85mm f/1.8, highlighting how prime lenses provide a very shallow depth of field and beautiful blurred backgrounds (bokeh) at a lower price point than professional zooms.
- 7:08 – Demonstration: The Kit Lens Limitation A live look at a camera screen showing how zooming from 18mm to 55mm automatically forces the aperture from f/3.5 to f/5.6, limiting your light.
- 8:57 – Low-Light Performance & ISO Explains the “hidden cost” of kit lenses: as the aperture narrows during zooming, the camera must raise the ISO, which can lead to grainy or “noisy” photos.
- 10:10 – Constant Aperture Zooms Why professional lenses (like a 70-200mm f/2.8) are expensive: they maintain the same wide aperture throughout the entire zoom range, providing consistent exposure and blur.
