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Beginner’s guide to Auto Focus modes and Focus areas

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Sara Rodriguez Martinez
  By Sara Rodriguez Martinez
Beginner’s guide to Auto Focus modes and Focus areas www.sleeklens.com

Focusing is one of the most basic (and important!) aspects of photography. If you manage to master it, your photos will reach a new level. Knowing how to set your focus correctly means you have the control over which part (or parts) of the photo is going to be sharp and which will be blurry.  You can draw the attention of people to or away from particular details in your photo by what you decide to put into focus and what not; focusing is adding a new communicative aspect to the photo.  First of all you need to decide if you want to use Manual or Auto Focus (AF) mode.

A photo with a correct focus, you can see both the teapot and cup appear sharp and well defined.

 

Here I decided that the teapot was the most important object of my image, so I focused on it. The teapot is sharp and the cup appears blurry. This effect naturally directs the eye of the viewer to the teapot.

 

This image was a complete disaster because all the elements are blurry. You can see here how the focus is such an important factor in photography. If you don’t do it correctly, you can lose a lot of photos.

Manual focus vs. Auto Focus (AF)

Both manual and automatic focus modes are available in most of the cameras today. When you focus manually you have complete control over the focus, but it is a process that takes a lot of practice to master. When you use manual focus mode you need to rely on your eye and your hand, simultaneously moving the focus ring on your lens and looking at how the image changes through the eyepiece of the camera. Sometimes less than a millimeter is enough to influence the results. Even for an experienced photographer, it can take time to set the focus correctly. The greatest downside of this is that you might miss photos just because you did not focus in time.

The focus ring on my AF-S DX Nikkor 18-140mm f/3.5-5.6 G lens.

Fortunately, cameras can help you focus using the AF (Auto Focus) mode. Basically, it means that the camera is moving the lens according to settings that you chose for it. This means the reaction time is much faster although you need to give up some of your control. In order to take the full advantage from your AF, you need to understand the different options you have.

A lot of lenses have a bottom that allows you to switch easily between Manual and Auto Focus.

Focal points are the basis of the AF

AF is based on focal points. The focal point is the area in the sensor that the camera will bring into focus. Depending on your camera, you might have more or less focal points to choose from. Nikon has from 1 to 51 focus points.  The main idea is always the same: the camera will focus on the area of the frame that is the focal point you selected.

There are several AF modes to choose from

The name of the AF modes might vary between camera manufacturers. In order to simplify, I will use only the Nikon terminology along this article. If you have another camera, don’t worry. Take your camera manual and have a look at the section about Auto Focus. You will find there all the information you need to recognize the AF modes. In Nikon the AF modes are called Single area focus mode (AF-S), Continuous focus mode (AF-C) and Single/Continuous Hybrid Mode (AF-A).

There are different ways to switch between AF modes and it depends on your camera. You might have a switch or a dial to select the different focus modes or you might need to go to the Menu screen and change it from there. Have a look at your camera manual to know how to do it.

In the Nikon D7000 you can change the AF modes using a switch located right at the base of the lens.

 

Other cameras (as the Nikon D3100) have no switch so you need to change the AF-mode through the menu.

Single area focus mode (AF-S) is perfect for static or almost-static photography

Single focus point is the simplest mode to use. This mode allows you to select just one focal point. It is useful when your subject is not moving (landscape) or if it moves just a little (some portraits). It allows you to lock the focus when you half-press the shutter release which is really useful if you want to reframe your photo and maintain the focus as it is.

AF-S mode is perfect for architectural photography. This photo of a modernist building was taken in Sitges, a town close to Barcelona (Spain). On the other hand, the woman at the bottom right is out of focus as she was moving (in this case it is a good thing as my main interest was the building)

Use Continuous Focus mode (AF-C) for tracking moving subjects

If you are taking photos of people doing sports, cars, kids, animals or any other things that move… you will find the AF-C mode really useful. The camera is not blocking the focus point when you press the shutter release halfway.  Instead, the camera adjusts the focus to the movement of your subject. This will allow you to keep your subject in focus all the time because you won’t need to refocus each time your subject moves. However, when you use this mode, you can’t reframe.

Taking photos of flying insects becomes easier when using Continuous Auto Focus.

Single/Continuous Hybrid mode (AF-A)

If you select this mode, your camera will decide if your subject is either static or moving and then it will select Single or Continuous mode respectively.  This mode might be useful for beginners because then you just let the camera decide and you can pay attention to other things (exposure, white balance…). However, your camera might make the wrong decision. For example, if you want to take a photo of a static flower and in the frame, there is also an animal moving, your camera might think you want to take the photo of the animal, select Continuous mode and you can end up with an animal in focus and a blurry flower.

Once you know the AF mode, it is time to choose the focus area

The focus area is related with how many focus points you are using and how they act. You have a selection of focus areas that you can use with each of the AF-modes. The most common ones are the Single-point AF-Area mode and the Dynamic AF-area mode. Let´s see what they are about!

In Single-Point AF-Area mode the camera uses just one focus point (the one you select in your viewfinder). It is a good option to take photos of stationary subjects such as landscapes, buildings or still life.

In some cameras (as the Nikon D3100), you need to access to the menu in order to change the AF-area modes. Other cameras have a button or a switch.

In Dynamic AF-area mode you also select just one focus point. But if the camera detects that the subject you are focusing on moves, it will use the surrounding focus points to track the movement. The fact that it will use just the surrounding ones means that you should keep your subject close to the initial focus point you selected (by following the movement of the subject with your camera). If the subject moves to the other side of the frame, the camera will probably lose track of it. Some cameras allow you to select the number of surrounding focus points: 9 focus points for a small area, 21 focus points or even 51 for the whole frame area.

There is a variation of the Dynamic AF-area mode called 3D-Tracking Mode. This mode is available in some Nikon cameras; it functions much like the Dynamic mode except that the camera keeps following the subject even if it goes out of the area covered by the focal points (9 or 21). The camera takes a bit longer to take the photo than the dynamic mode (if set on 9 or 21 focal points) but it gives a bit more room for error with estimating where the moving subject will be.

There are other area modes such as the Auto-Area AF Mode (the camera decides which one to use), group-area mode, face-priority AF… but the Single point and Dynamic AF-Area are the basic ones and can cover the most part of photo situations. If you are a beginner, I recommend you to start by using these two modes in order to keep it easier. You can always check the other modes once you master them. Here you have a table that combines the AF-modes with the Focus areas.

I hope you find this article useful. Feel free to comment below. Have a happy shooting!!

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Sara Rodriguez Martinez
I am a biologist and a self-taught photographer based in Barcelona (Catalonia). Buddhist philosophy has a strong influence on me: I have a deep appreciation to life and I give a huge value to the little things that makes our days happier. I became a passionate about photography when I got my first camera and I understood that photography allows me to express my way of approaching life. I love learning so I am always willing to trying new things. These days I am shooting mostly nature and portraits.

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