This is one of the first theoretical lessons that we should learn in 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 sharp, 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 ? . For this reason, 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 THE DIAPHRAGM APERTURE?
The aperture of the diaphragm is what regulates the amount of light that passes through our objective towards the camera sensor. The diaphragm is part of any lens, and is made up of a series of plates or fins that move in or out, forming a more or less large circle, moving toward the center or outward through which more or less light passes. , depending on its diameter.
HOW ARE F/?-VALUES INTERPRETED?
The different diaphragm openings are measured or named through numbers or values in f/ . Depending on the luminosity of the objective, we will have smaller or higher minimum f/ values.
Here comes what I think is the most important thing and what usually messes us up when we start and try to understand the aperture. The lower the f/ value, the more light that will enter through the lens , and the higher the f/ value, the less light that will enter through the lens.
Look at the following image and imagine that the light must pass through those "holes". Through which of them do you think the greatest amount of light will enter? f/2, right? And conversely, 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 step is nothing more than the jump from one f/ value to the next . For example, in the image above we would say that between f/2 and f/2.8 there is one stop. Or between f/2 and f/4, there are two f-stops.
And you will say… Very well, and what does that mean? Well, each step up the scale means that you are halving the amount of light coming through the lens. (For example f/4 has half as much light as 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 the following:
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
Now, the previous steps are considered integers , the classics, the theoretical ones. But as always, things are evolving and it is very possible that, today, your camera has many more f/diaphragm numbers than the ones we have discussed, right? Surely you were wondering what to do or where values like f/3:5 or f/5 come from. Well, all the values that are between the different steps are what we consider as intermediate steps.
The intermediate steps are not universal and have been added to allow more fine tuning of the aperture.
THE BRIGHTNESS OF THE LENS AND THE APERTURE OF THE DIAPHRAGM
When we talk about more or less bright lenses, we are actually talking about the maximum aperture capacity associated with them.
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:
- That the focal length of the objective varies between 18mm and 55mm.
- That the maximum aperture of the diaphragm is f/3.5 at its minimum focal length (18mm)
- That the maximum aperture of the diaphragm is f/5.6 at its maximum focal length (50mm)
That is, with this objective, 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 objective only indicates the maximum aperture and the fixed focal length: 50mm 1:1.4. That is, the maximum aperture of this objective is f / 1.4.
Between the two examples (zoom and prime) the 50mm prime is the brightest lens.
THE DEPTH OF FIELD AND THE OPENING OF THE DIAPHRAGM
I remember when I started in this photographic passion, that one of the things that fascinated me the most about an image was the blurred 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 diaphragm aperture and its relationship with depth of field ?
The aperture of the diaphragm 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. The larger the diaphragm opening (small f/value), the smaller the depth of field or focused area in the image and, conversely, the smaller the diaphragm opening (high f/value) the greater the depth of field or focused area in the image.
In short, large openings will not only allow more light to enter, but you will also be able to focus attention through the blur it provides. On the contrary, if what you want is a great depth of field or to reduce the entrance of light, you should close the diaphragm.
THE SHARPNESS AND APERTURE OF THE DIAPHRAGM
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 the Sweet Spot of the Lens or Sweet Spot . Contrary to what it may seem, the sweet spot is not located at either end of the diaphragm opening, but rather at intermediate openings , but it depends on each lens and the focal length used. Just remember that if you want “extra” sharpness you should try not to be at the extremes of the aperture or the focal length, because that is where the “worst” or more aberrations produce the objectives as a general rule.
EXPOSURE TRIANGLE
Lastly, 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's worth the effort, you'll see
I know that it may seem complicated to you, but it is not at all. Of course, it requires that you stand in front of your objective and that you 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 the diaphragm 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 you to internalize this concept. Once you do, you can play with the opening in a myriad of ways. I'm sure you won't have fully internalized it at all, you'll imagine the scene you're looking for, and you'll know exactly what parameters to give the camera to get the image you want. You do not believe me? Practice a bit and you will see how this will happen sooner than you imagine ?
