What is Aperture?

Photography stands on three main pillars: Aperture, Shutter Speed, and ISO. In this post, we will focus on Aperture—the system that determines the intensity and volume of light reaching the sensor (or film).

The word comes from the French "diaphragme" and is often referred to as "Aperture" (meaning opening) in English.

The Water Tap Analogy

To understand exposure easily, imagine a glass being filled with water.

• Aperture is like the tap: it controls how much water (light) flows at once.

• Shutter Speed is the duration: it determines how long the tap stays open. To get a perfectly filled glass (a correct exposure), these two must work in harmony.

Like the Human Eye

The mechanism of aperture is very similar to our eyes. When we enter a dark room, our pupils get larger to let in more light so we can see better. In bright sunlight, our pupils get smaller to protect our eyes from the glare.

As you can see in the photos, the aperture changes its size by moving the aperture blades. We measure this opening with the "f" value.

Understanding f-numbers

Depen ding on your lens, these values usually range from f/1 to f/36.

Important Rule: The larger the number, the smaller the opening.

This means at f/1.8, your lens is wide open (lots of light), but at f/22, the opening is very small (very little light). Each "stop" in these values either doubles or halves the amount of light reaching the sensor.

Aperture and "Depth of Field"

Aperture doesn’t just control light; it also controls Depth of Field (DoF).

• Small f-value (e.g., f/1.8): You get a shallow depth of field. This means your subject is sharp while the background becomes beautifully blurry. This is perfect for portraits when you want to remove "visual noise" behind your model.

• Large f-value (e.g., f/11 or f/16): You get a deep depth of field. Everything from the front to the back remains sharp. This is the gold standard for landscape photography.

Why I Prefer "Aperture Priority" Mode

On your camera dial, you will see an "A" (Nikon, Sony, Fuji) or "Av" (Canon). This is Aperture Priority Mode.

In this mode, you manually choose the aperture (f-value), and the camera automatically calculates the correct shutter speed.

Why is it so useful? It’s fast. Since my main subjects are usually people, I need to be quick. This mode allows me to decide instantly: do I want to isolate the person from the background or show the life continuing behind them? I choose my "f" value, and I let the camera handle the rest while I focus on the "moment."