Diaphragm Aperture Explained With Examples

This is one of the first theoretical lessons that we should learn photography, because once you know how the aperture works, you will be able to understand and create most images that come to mind.

Surely many times you have wondered why some images get a blurred background, or totally clear, or how to be able to take pictures in low light and without flash…

If you are still in the automatic mode of your camera, these are unknowns that you will never solve 😉 . That is why I invite you to dare to practice with the semi-automatic modes and with the manual mode after having taken a look at this article.

What is Diaphragm Aperture?

The diaphragm opening is what regulates the amount of light that passes through our lens to the camera sensor. The diaphragm is part of any objective, and it is made up of a series of plates or fins that move inwards or outwards forming a more or less large circle, do it towards the center or towards the outside through which more or less light passes. depending on its diameter.

How are f/? values ​​interpreted?

The different diaphragm openings are measure or denominate through the numbers or values ​​in f/. Depending on the brightness of the lens, we will have smaller or larger f/minimum values.

Here comes what I think is the most important and what often confuses us when we start and try to understand the aperture. How much the lower the f/ value, the more light will enter through the lens, and the higher the f/ value, the less light will enter through the lens.

Look at the following image and imagine that the light must pass through these “holes”, through which of them do you think the greatest amount of light will enter? f/2, right? And on the contrary, through which of them will the least amount of light enter? Well, in this case it would be f/22, but these apertures are always defined by the lens.

What are diaphragm steps?

The diaphragm passage is nothing more than the jump from one f/ value to the next. For example, in the previous image we would say that between f/2 and f/2.8 there is an aperture stop. Or between f/2 and f/4, there are two aperture steps.

And you will say… Very well, and what does that mean? Well, each step up the scale means you are halving the amount of light coming through the lens. (For example f/4 has half the light of f/2.8). And on the contrary, each step down that you take on the scale means that you will be multiplying the light input by two compared to the previous step. (For example f/8 has twice as much light as f/11).

The “standard” scale would be as follows:

f/1, f/1.4, f/2, f/2.8, f/4, f/5:6, f/8, f/11, f/16, f/22, etc.

intermediate steps

However, the previous steps are considered integers, the classics, the theoreticians. But as always, things are evolving and it is very possible that, today, your camera has many more f/diaphragm numbers than those we have mentioned, right? Surely you were wondering what to do or where values ​​like f/3:5 of/5 come from. Well, all the values ​​that are between the different stepsare what we consider to be intermediate steps.

The intermediate steps are not universal and have been added in order to more precisely adjust the aperture.

The brightness of the lens and the aperture of the diaphragm

When we talk about more or less luminous objectives, we are actually talking about the maximum diaphragm opening capacity that they are associated with.

As we have seen in the previous point, the lower the f value, the more light enters through the lens and therefore, we consider it brighter.

For example, an 18-55mm 1:3.5-5.6 zoom lens tells us several things:

  1. That the focal length of the lens varies between 18mm and 55mm.
  2. That the maximum aperture of the diaphragm is f/3.5 at its minimum focal length (18mm)
  3. That the maximum aperture of the diaphragm is f/5.6 at its maximum focal length (50mm)

In other words, with this lens, we can open the diaphragm up to a maximum of f/3.5 when working at 18mm, and a maximum of f/5.6 at 50mm.

In fixed optics, the lens only indicates the maximum aperture and the fixed focal length: 50mm 1:1.4. That is, the maximum aperture of this lens is f / 1.4.

Between the two examples (the zoom and the fixed lens) the 50mm fixed is the brightest lens.

depth of field and aperture

I remember when I started in this photographic passion, that one of the things that most fascinated me about an image was the out-of-focus backgrounds, the possibility of enhancing an area of ​​the image only through the focus. Obviously I didn’t have much idea how to achieve what for me was an almost magical effect… Until I got a SLR and discovered the aperture and its relationship with depth of field 😉

The diaphragm opening is closely related to what we know as depth of field, which is nothing more than the amount of area in focus in the image. A more diaphragm opening (small f/value), shallower depth of field or area in focus in the image and, conversely, to smaller diaphragm opening (High f/ value) the greater the depth of field or area in focus in the image.

In short, large apertures will not only allow more light to enter, but you will also be able to focus attention through the blurring it provides. On the contrary, if what you want is a lot of depth of field or to reduce the entrance of light, you will have to close the diaphragm.

At wider apertures (low F) shallower depth of field
Closer diaphragms (high F) allow greater depth of field, ideal for landscapes

Sharpness and aperture

The aperture of the diaphragm is also related to the sharpness of the image. All lenses have an aperture at which they achieve maximum sharpness, which is also known as Sweet Spot of the Objective or Sweet Spot. Contrary to what it may seem, the sweet spot is not located at either end of the diaphragm opening, but rather it is located at the intermediate openings, but it depends on each lens and the focal length used. Just remember that if you want an “extra” sharpness you should try not to be at the extremes of the aperture or the focal length, because that is where the “worse” or more aberrations produce the lenses as a general rule.

exposure triangle

Finally, don’t forget that an image is made up of several interrelated parameters. The most important are what we know as the exposure triangle: Speed, ISO Sensitivity and aperture. Through the knowledge and relationship of these three parameters, you will be able to achieve almost any photograph that you propose 😉 It is worth the effort, you will see 🙂

exposure triangle

I know that it may seem complicated to you, but it is not at all. Of course, it requires you to stand in front of your lens and memorize while you open and close the diaphragm. “If I open the diaphragm more light enters, less depth of field, low f/ value”, “If I close the diaphragm I see that the hole in it is smaller, so less light enters, more depth of field, f/ value higher”. Or as it goes well for you 🙂

It doesn’t matter how long it takes to internalize this concept. Once you do, you can play with the opening in so many ways. Surely you will not have it completely internalized at all, you will imagine the scene you are looking for, and you will know exactly what parameters you have to give the camera to get the image you want. You do not believe me? Practice a little and you will see how this will happen sooner than you imagine 🙂

I hope this article has been useful to you. If so, please share it with someone else you think might be interested in learning about aperture. Thank you very much and until next time 🙂