Surely, it has happened to you that you had the perfect moment for a photo but when reviewing the result you realize that the picture is blurry or not as sharp as you expected. The causes can be many reasons, starting with a jitter produced by an incorrect shutter speed, but it is also very common that the cause is a bad focus because we have made a poor choice of the AF mode of our camera.
This problem is common with beginners and amateurs, perhaps one of the latest batch that incorporates hybrid AF systems with a multitude of focus areas and very sophisticated logarithms that promise precision and speed never seen in photography. . However, in practice they are not always what they promise or require a learning period, in addition to making it necessary to have very clear concepts about the different autofocus modes.
As you know, there are basically two modes, the AF-S (single or simple autofocus, also known as One Shoot) and the AF-C (continuous autofocus, also known as AI Servo), plus a third, the AF-A (autofocus automatic) that appears on most modern cameras. In these ways we have spoken several times (including of course in our Photography Course), but now we are going to review them from a practical point of view. That is, paying particular attention to when we should use one mode or another depending on the scene in question that we want to capture.
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Choosing the focus area
But first we must talk about another feature that is crucial to know how to use AF well, and that is none other than the choice of the focus area to use and, consequently, the number of focus points that will come into play.
What we should know is that, apart from the different AF modes, you can also choose between different ways of selecting the area or focus point. In this we are not going to go into depth, since they depend a lot on the type of camera, but it is convenient to know that we can choose (basically) between the camera deciding what is the preferred focus point or area at all times or that we do it we.
Obviously, this second option is the one we recommend the most but we also have to know that we can choose several options. One would be the most classic and consists of deciding that the camera focuses only on the central point / area, and reframing if necessary. The other, more modern (and available depending on the model), is the one that makes it possible to choose on the fly the place (point or area) where we want the camera to focus.
The first option, that of letting the camera do the work itself, we recommend less because it is evident that cameras do not always behave as expected, especially in situations with many elements or when they move quickly. In these cases, it is where the most advanced cameras shine, the professional type, which usually incorporate very sophisticated focusing systems and algorithms.
For the rest, although the models are becoming more advanced and are even capable of following faces automatically, it is better to resort to manual selection of the place where we want to focus. Although everything is a matter of knowing and thoroughly testing your camera to know how reliable its AF system is.
If the subjects are not moving
We now move on to the modes of approach themselves and, as we mentioned, we do so taking the situation into account. The first would be the one that perfectly describes the title, when the element that we want to capture does not have movement, for example a still life or a static landscape.
In this case, the choice is clear and the ideal mode is the single autofocus, AF-S, which focuses taking into account the distance at which the subject is in the chosen area point. Thus, the element will remain sharp (as long as it does not move) since the camera will lock the focus at that point while we keep the shutter-release button pressed halfway (or the AF-On button).
Thanks to this system we can easily make a change in the composition of the photograph once we have focused. For example because we have done it with the central point but we do not want the focused subject to be centered. For these cases, by the way, leaving the choice of focus point to the camera is not the most recommended, in fact it would even be more advisable to focus manually.
If there are moving parts
The opposite case, that of the subjects in which there are moving subjects, are in which we have to opt for continuous autofocus, AF-C, which will take care of keeping the element in question focused even though it moves ( and as long as we press and hold the appropriate button). The best example is action and sports photography, where the use of this focus mode is more than widespread and much needed.
For these cases, it might be advisable to let the camera choose the focus point or area, but always sticking to what we said before: To the solvency of our camera for moving focus. Because it will be useless if we are focusing continuously if what we have selected is not what we want to focus on. Therefore, lately we are seeing modern systems that allow to choose the AF point / area very quickly through the touch screen or by means of a small joystick.
If the subject does not move but can be …
It would be a third option associated with the automatic autofocus mode, AF-A, which, as you may have already assumed, is a hybrid between single and continuous AF. This system focuses in principle like the static mode, focusing on a stationary subject, but it can vary the focus if this subject begins to move, as would be the case for example with portraits photography.
In portrait photography, the AF-A mode can help prevent possible out of focus if the subject moves unintentionally. Photo by Prasanna Kumar
That is, it is a mode that combines the best of the other two, so in principle it is highly recommended to choose it by default. Although again the most important thing is to know the capabilities of our camera and how it behaves, to decide one way or another when shooting.
Other things to consider
We finish with those other little things you should know, especially if you are a newbie, to make sure that you are not going to have a blurry photo due to the focus system. The first for example is that you take into account the minimum focusing distance of the lens you are using, lest your camera not focus because you are too close (it happens more often than it may seem).
Another reason that can cause the focus not to be correct is that you are trying to focus on a complicated subject, that has little contrast, or in a situation of very low luminosity that prevents the AF system from working correctly (there again everything depends on your camera in particular). And a third problem that can negatively affect the focus of an image is that we are working with an extremely shallow depth of field that makes it very difficult to hit the exact point.
Be that as it may, practice and deep knowledge of the capabilities of our camera, to choose the correct configuration in each case, are the best way to ensure that the focus is going to be the right one. If you have mistakenly shot a blurry photo you can also use some fixing apps trying to give it the right shapes.
As always, we hope that the article is helpful and we thank you for your contribution via comments.
