Photography 101- F-Stop and Aperture

F-Stop and Aperture

How was your week? Good? Any good stories to tell? Please, do tell! Post them below.

So for the next two sessions, I want to go over two of the most important factors that have ever been presented to the photography industry. F-stop (Aperture) and Shutter speed. These are the bread and butter that dictate the kind of image that you are going to get! Knowing how to operate these factors efficiently can be the difference between “a” shot and “THE” shot. They work hand in hand, much like a marriage, to produce the product. A+B=C. You can’t have one without the other. No I may end up diving into some mathematical terms during my talk on these subjects. So first, a math joke…

Now on to Aperture!

An image is created through light. Light illuminates everything around us. Without light, we would not be able to see all of the beauty that God has blessed this world with. Photography is our way of capturing that beauty. But this would be impossible without light. One of the best ways to start off describing aperture to by comparing it to an eye. Think of your pupil. Think about how you squint when it is bright out. If you are reading this with someone, go in a room and turn out the lights while looking at each other. Wait 5 seconds, then turn them back on while watching the other’s pupils. Did you see how they adjusted?

Aperture works the same way. In terms of photography, aperture is the mechanism that determines how much light to let in when exposing a photograph. One of the things to get used to is the fact that a lot of the factors of photography are inversely related. Aperture definitely follows suit to that. The more light the aperture lets in, the lower the f-stop. Inversely, the less light the aperture lets in, the higher the f-stop. Think of Aperture as a hole. The smaller the hole, the less amount of light is let in. when would you not want a lot of light to pass through your camera? Think logically. When there is too much of it. Think about when you flip that light switch back on. What happened to your pupil size? It shrank.

In terms of aperture numbers, when the hole is smaller, the number is bigger. Again, think inversely. When we want more light in, the hole gets bigger, the aperture number gets smaller. In relation to the shutter speed, the more light that is let in, the faster the shutter speed has to be. The less amount of light that is let in, the slower the shutter speed has to be. If you have a low F-Stop like 2.8, then you are going to want a fast shutter speed such as 1/250. When you have a larger F-Stop such as 22, you are going to want a much slower shutter speed such as 1/30. But we will focus more on shutter speed next time. For now back to aperture.

Ok! Welcome back. Let’s take a look at the mathematical equation for aperture.

This equation represents 3 variables. The F-number is represented by N, f is the focal length, and D is the diameter of the entrance hole. The vast majority of lenses have the ability to adjust the hole, as seen in the photo above, by means of a diaphragm. This diaphragm “stops” up or down to adjust the amount of light that you need per the exposure that you want.

GREAT. Now we that we are up to speed on what a F-stop actually is, how does this benefit our photos?

I’m glad that you asked that young wonderer.

Have you ever looked at a rock, or a flower really close? What happens to everything else while you focus on that rock? If goes OUT of focus correct? This is a phenomena known as Depth-of-Field (DOF), of which there are two types. Shallow and Deep. DOF refers to the distance of focus in an image. This focal distance is very useful in separating a subject from its background or putting everything in focus for more emphasis on environment. The lower the f number, the more shallow the DOF, inversely, the larger the f number, the deeper the DOF. Selective focus, or bokeh as its referred to in film, is a useful tool in story telling through your photography. This can also be applied to portraiture and macro photography. A deep DOF where everything is in focus is helpful in things like landscape photography and astrophotography.

Here, let me clear it up a little better through some pictures.

Notice how everything is in focus. This type of photography is really helpful when we are looking to have multiple points of interest. We find this style namely in landscape photography.

Notice how the background is blurred and out of focus. When used appropriately, bokeh can give us a beautiful effect isolating the focus to one subject. This is particularly useful when we want our viewer to focus on just one portion of the picture. Typically, we find this in portraiture. It is often used to create drama to a scene and give it some life and purpose.

Make sense? Another thing that aperture affects is the sharpness of the image. Modern lenses are typically most sharp when the f-number is between f/5.6-f/8. This is definitely something to consider when shooting. Being a portrait photographer, as well as a cinematic filmmaker, I am a huge fan of shallow DOF. But that is not without its troubles. It can be difficult to focus manually the shallower (lower f-number) the focus is, due to the fact that the focal plane is so small.

So that about wraps it up! Welcome to the wonderful worlds of Aperture! Next time, we are going to tackle Shutter Speed, so be prepared for some stop-go motion!

Till next time!

Josh D. Smith