A Simple Explanation of Aperture

If there’s one thing about photography that confuses newcomers(and often the rest of us) it’s the idea of aperture. What is it? Why is it so complicated? How does it affect your photos? Well, aperture isn’t complicated or impossible to understand, it’s just unfamiliar. And like most unfamiliar things the more you learn to about it the less intimidating aperture will be.

In this article I’m going to show you just how not complicated aperture can be. You’re going to learn the basics of aperture and how it relates to the focus and shutter speed of your photographs.

Aperture and the Dreaded F-Number

Let’s start off by explaining what aperture is and how it is measured. The idea of aperture in reality is astoundingly simple and there’s honestly only a few things you truly need to know to conquer the subject.

What is Aperture?

OK, let’s just get this out of the way right off the bat…aperture by its very definition is simply a hole. As it pertains to photography, aperture is the hole in the lens where light passes into our cameras. That’s it.

See, not so scary! However, the way aperture is measured is the cause for anxiety in some because, there again, it’s measured in a fashion that most of us don’t readily understand. But don’t worry, much like everything it becomes easy once you understand one fundamental thing….

F-Numbers

Trust me. You are neither the first nor the last  person to be completely perplexed when it comes to understanding the way aperture is measured. The notion of ‘F-Numbers”(sometimes called f-stops) has been the source of a lot of confusion because they simply don’t make much sense in terms of how we normally think about our physical world. In short, the F-Number is nothing more than a ratio between the focal length of the lens and the diameter of the aperture being used. So an aperture of F4 means that the focal length is four times larger than the selected aperture. An aperture of F8 means that the focal length is eight times larger and so on and so forth. Now this is where things get a little weird….The larger the F-Number, the smaller the actual opening. The smaller the F-Number the smaller the actually opening. Look at this quick example:

It’s going to be OK…take a deep breath and realize that it actually makes sense mathematically but you’re not going to have to understand anything more in depth than that for most practical purposes. Just know that it the larger the physical opening of the aperture the smaller the F-Number will be.

Aperture and Depth of Field

There are a surprisingly large amount of factors that determine the final depth of field or your image and aperture size is one of them. Generally speaking, the wider the aperture(smaller F-Number) the more shallow depth of field will become. This means that smaller apertures(larger F-Numbers)  will bring more of the scene into the range of focus than will larger apertures. Take a look at these Chess pieces and see what I mean.

Not only does aperture play a key role in focusing but it also spills over into your shutter speed. Speaking of shutter speed….

Aperture and Shutter Speed

The relationship between aperture and shutter speed is extremely simple and yet extremely important. Simply put, larger apertures allow more light to enter through the lens. More light means faster shutter speeds can be used. This is where the phrase “fast lenses” comes from because lenses with larger aperture allow for faster shutter speeds.

So, faster lenses with wider maximum apertures are capable of shooting more effectively in low light conditions because they allow more light to pass through them.  A lens with a maximum aperture of F2.8 is considered to be “faster” than a lens with a maximum aperture of F4.

Final Thoughts on Aperture

In a way all this might sound like an oversimplification but it’s essentially all you really need to know about aperture. The manner in which aperture selection relates to depth of field and shutter speed will take you a long way in photography. Aperture isn’t scary! Having this simple knowledge will help you better understand exposure, make smarter lens choices and generally control your images much more effectively.