select an auto-focus mode

Now things get a bit technical. However this is some of the best gold that every photographer must know.

Auto-focus Modes

Cameras have a variety of focus modes. You can shoot in Manual focus, or Auto-focus. You can shoot moving subjects or stationary subjects. This lesson has a lot of technical nuance and it may be a bit confusing, however, this is a key lesson in photography and without it you are basically using your camera as a fancy point an shoot.

On most lenses, there is a switch on the side of the lens which allows you to move back and forth from Manual and Auto-focus. On some cameras, this toggle is in the digital menu of the camera.  For the purpose of this lesson, we are always going to be using Auto-focus, so ensure that your Manual/Auto-focus switch on the lens is set to Auto-Focus.

When you are shooting in Auto-focus, there a few options within the auto-focus system that we need to select and the main question you need to ask yourself is, am I shooting a moving target or a stationary target. For now, we are going to work under the assumption that we are shooting a stationary subject, like the coffee mug on your desk.

Auto-focus mode vs being in Auto-focus.

For most things we shoot, the auto-focusing systems on modern cameras are far better than our eyeballs and certainly much faster. I encourage you to shoot in auto-focus wherever and whenever possible.

In the heading above, I mentioned that there is a switch on the side of the lens which allows you to move back and forth from Manual and Auto-focus. On some cameras, this toggle is in the digital menu of the camera.  This is what we mean when we say shooting using auto-focus. What most people don’t realize when they start is that once you are in auto-focus you need to select a mode within auto-focus. Don’t panic, this will become much more clear. For the purpose of this lesson, we are always going to be using Auto-focus, so ensure that your Manual/Auto-focus switch on the lens is set to Auto-Focus.

EXERCISE: On the side of the lens, set the focus mode to AF or A. If you are shooting with some nikon 3000 series cameras, Sony cameras and a few others, you may need to go into your display menu to set the focus mode. Check your manual to find out how to set the autofocus mode.

Auto-focus modes on a Nikon, Sony, Pentax or Olympus camera.

If you are using a Nikon, Sony, Pentax or Olympus camera the options for auto-focus mode are the following.

• AF-S    Single Shot Auto-focus
• AF-A    AutoSelect Auto-focus Mode. (Some cameras will not have this option)
• AF-C    Continuous Auto-focus

This setting may not be the easiest to find on your camera, but its important so dig into the manual and find out how you set the focus mode for your camera model.

EXERCISE: Set the auto-focus mode to AF-S

Auto-focus modes on Canon.

If you are using a Canon camera the options for auto-focus mode are the following.

• ONE SHOT    Single Shot Auto-focus
• Ai Focus     Auto-Select Auto-focus Mode. (Some cameras will not have this option)
• Ai Servo     Continuous Auto-focus

This setting may not be the easiest to find on your camera, but its important so dig into the manual and find out how you set the focus mode for your camera model.

EXERCISE: Set the auto-focus mode to ONE SHOT

How the camera focuses. Language Matters.

Most people think of how the camera focuses incorrectly. Over the past 15 years manufacturers have been steadily increasing the number of focus points within the viewfinder. This can be helpful in some shooting situations however it has caused a lot of confusion for those just starting out. The multiple focus points within the viewfinder give a sense that somehow the camera is able to focus on many different things at once. This simply does not happen. 

The language we use when we speak about taking photos is always slightly incorrect. You likely say things like “focus on the eyes” or “focus on that tree” or “I focused on the babies toes”. This isn’t exactly the way it works. When we see something we want to photograph, we use the cameras autofocus system to measure a distance to the thing we want to appear in focus. The camera does not know what you are shooting and it can only measure to one distance. This means that if you or your subject move before you have pulled the trigger, then likely your subject will no longer be at the correct distance as measured when you were focusing.

All this is meant to say that when you pull the trigger halfway to focus on the subject, its simply measuring a distance. It’s not focusing on eyes or toes or trees or anything else for that matter. The camera with your help is measuring a distance. 

Single shot auto-focus. ONE SHOT/AF-S

The camera focuses one shot at a time. Single shot auto-focus is your default position. For most subject matter, being in single shot focusing will allow you to compose your photos and get pinpoint accurate focus on the area of the photo that you desire.

With your camera set to ONE SHOT (Canon) or AF-S (All other cameras) you will be able to press the shutter release button halfway to focus. I call this action, feathering the trigger. Feather the trigger halfway and the camera will attempt to focus on the subject. When the camera acquires focus and you keep your finger depressed halfway on the shutter release button, the camera will STOP FOCUSING.

At this point the camera has found focus and has locked the focus distance based on that subject. NOTE: If you lift your finger purposefully, or inadvertently the process of focusing needs to start all over.

EXERCISE: While looking through the viewfinder, press the shutter release button halfway and slowly point the camera at different objects and attempt to focus. When the camera is focused you may hear a beep. This is the camera telling you that it has measured the distance and you are now ready to finish the shot. Move on to a new subject. 

Continuous auto-focus. SERVO/AF-C

Continuous auto-focus is a different animal. In the paragraph above, I stated that we use ONE SHOT/AF-S focus mode as the default auto-focus setting. Continuous auto-focus is only ever used when we have moving subjects.

NOTE: Moving subjects are defined as subjects that are changing their distance from the camera from shot to shot. Some standing in place and waving or jumping up and down is not a moving subject as far as the camera is concerned. The determining factor as to whether you use ONE SHOT/AF-S focusing or SERVO/AF-C focusing is answered by: Is the subject changing distance from shot to shot. If the answer is yes then shoot in Continuous/SERVO/AF-C.   More on this in a bit.

When you press and hold the shutter release button half way, the camera will focus but you will find that the camera never actually locks on the focus. As you move slowly from one subject to another, without taking your finger off the trigger, you will find that the camera re-focuses on the new subject. In fact, the camera never stops focusing. The reason for this is that the camera is trying to ensure that whatever is hitting the chosen focus point, is staying in focus, even if it changes distance from camera position.