Understanding What Focus and Release Priorities Do During Autofocus

Many new users of Nikon DSLRs have a peculiar difficulty when trying to use the AF-C (Continuous-servo autofocus) setting on their cameras. AF-C allows you to hold down the Shutter-release button and shoot bursts of many images in rapid succession. Unless you understand the differences between Focus priority and Release Priority when using AF-C, some of your images will simply be out of focus. If your camera is set incorrectly for your style of shooting, you can even have focus problems when using AF-S (Single-servo autofocus), where you only take one picture for each press of the Shutter-release button.

Note: Focus priority means that the camera will take a picture only when it can focus on your subject. Release priority means that the camera will take a picture even when it can't get good autofocus. Why would a camera even have a Release priority if it can cause out of focus images? We'll see.

Let's examine two specific Custom Settings—a1 and a2—in your Nikon. You'll find the settings when you press the Menu button and find the Custom Setting Menu, which is the third menu down, under the Playback and Shooting Menus. You'll find a1 and a2 under the Custom Setting Menu heading called a Autofocus. These two Custom Settings allow you to choose Focus priority (Focus) or Release priority (Release) for AF-C and AF-S modes.

First, we'll examine what the settings do and then see how to adjust them. Why not get your Nikon before you read on and be prepared to adjust these settings as you better understand them.



Using Custom Settings a1 and a2

Two of the more important Custom Settings are a1 AF-C priority selection and a2 AF-S priority selection. This special section will help you understand why you must pay very close attention to these two settings.

Again, Focus priority simply means that your camera will refuse to take a picture until it can reasonably focus on something. Release priority means that the camera will take a picture when you decide to take it, whether anything is in focus or not!

Now, you might ask yourself why there is such a setting as Release priority. Many professional photographers shoot high-speed events at high frame rates—taking hundreds of images—and use depth of field (or experience and luck) to compensate for less than accurate focus. They are in complete control of their camera’s systems since they have a huge amount of practice in getting the focus right where they want it to be. There are valid reasons for these photographers not to use Focus priority.

You need to ask yourself, "What type of photographer am I?" If you are a pro shooting hundreds of pictures of fast race cars, Focus priority may not be for you. However, for average photographers taking pictures of their kids running around the yard, deer jumping a fence, beautiful landscapes, flying birds, or a bride tossing a bouquet, Focus priority is usually the best choice. For most of us, it’s better to have the camera refuse to take the picture unless it’s able to focus on our subject.

When you’re shooting at a high frame rate, Focus priority may cause your camera to skip a series of out-of-focus images. It will slow your camera’s frame rate so that it will not reach the maximum number of frames per second, in some cases. But, I have to ask, what is the point of several out-of-focus images among the in-focus pictures? Why waste the card space and then have to weed through the slightly out-of-focus images?

Pay special attention to these two settings. You will need to decide—based on your style of shooting—whether you want your camera to refuse to take an out-of-focus image. If you set a1 and a2 to Focus priority and you try to take an out-of-focus image, the Shutter-release button will simply not release the shutter. The little green focus indicator in the Viewfinder will have to be on before the shutter will release.

Let's see how to adjust these two Custom Settings next:




Custom Setting a1 – AF-C Priority Selection

The a1 AF-C priority selection setting is designed to let you choose how your autofocus works when using Continuous-servo autofocus mode (AF-C). If you configure this setting incorrectly for your style of shooting, it’s entirely possible that a number of your pictures will be out of focus. Notice in the upcoming figure 1, image 3, that there are two specific selections, as follows:

Release Priority for AF-C 

If the image must be taken no matter what, then you will need to set AF-C priority selection to Release. This allows the shutter to fire every time you press the Shutter-release button, even if the image is not in focus. Releasing the shutter has priority over autofocus. If you are well aware of the consequences of shooting without a focus guarantee, then use this setting to make your camera take a picture every time you press the Shutter-release button. Your camera will shoot at its maximum frames per second (fps) rate since it is not hampered by the time it takes to validate that each picture is in correct focus. You’ll need to decide whether taking the image is more important than having it in focus.

Focus Priority for AF-C

This setting is designed to prevent your camera from taking a picture when the Focus indicator in the Viewfinder is off. In other words, if the picture is not in focus, the shutter will not release. It does not mean that the camera will always focus on the correct subject. It simply means that your camera must focus on something before it will allow the shutter to release. Nikon cameras do a very good job with autofocus, so you can usually depend on the AF module to perform well. The Focus setting will drastically increase the chances that your image is in correct focus.

Figure 1 – Setting Focus or Release priority for a1 AF-C priority selection

Use the following steps to select a Shutter-release priority when using a1 AF-C priority selection:

1. Select a Autofocus from the Custom Setting Menu and scroll to the right (figure 1, image 1).
2. Highlight a1 AF-C priority selection and scroll to the right (figure 1, image 2).
3. Choose Release or Focus from the menu (figure 1, image 3), with full understanding of what may happen if you don’t choose Focus (out-of-focus pictures).
4. Press the OK button to select your Shutter-release priority.

My Recommendation: Since I’m not a sports or action shooter, I choose Focus. Even if I were an action shooter, I would choose Focus. If I were a professional action shooter with many years of experience I may choose Release because I understand how to get good focus without autofocus in fast moving events.



Custom Setting a2 – AF-S Priority Selection

The a2 AF-S priority selection setting is very similar to a1 AF-C priority selection. It also allows you to choose whether the camera will take a picture with something out of focus. With this setting, you set the shutter-release priority for Single-servo autofocus mode (AF-S). It you set it incorrectly for your style of shooting, many of your pictures may be out of focus. There are two modes to choose from, as follows:

Release Priority for AF-S

A photo can be taken at any time. This can lead to images that are out of focus unless you manually focus each time you take a picture. The camera’s priority is releasing the shutter when you press the Shutter-release button, and it will do so even if nothing is in focus.

Focus Priority for AF-S

The image must be in focus or the shutter will not release. This means that the shutter won’t release unless the Focus indicator in the Viewfinder is on. This is the closest thing to a guarantee that your image will be in focus when you press the Shutter-release button. However, if you are focused on the wrong part of your subject, the camera will still fire.

Figure 2 – Setting Focus or Release priority for a2 AF-S priority selection

Use the following steps to select a Shutter-release priority when using a2 AF-S priority selection:

1. Select a Autofocus from the Custom Setting Menu and scroll to the right (figure 2, image 1).
2. Highlight a2 AF-S priority selection and scroll to the right (figure 2, image 2).
3. Choose one of the two settings from the menu, with full understanding of what may happen if you don’t choose Focus (figure 2, image 3).
4. Press the OK button to select your shutter-release priority.

My Recommendation: I choose Focus priority when using AF-S. I love pictures that are in focus, don’t you? When I want to manually control focus, I’ll just flip the switch to manual on the camera or lens and focus where I want. 

With the information above you may have a better understanding of Focus and Release priority. Please experiment with these settings and determine how you want to set them. The camera comes from the factory with Custom Setting a1 – AF-C set to Release priority. Custom Setting a2 – AF-S set to Focus priority. Of course, if you purchased a pre-owned camera, or have been fiddling with the settings previously, they may be set to either of the two choices. Learn to use these settings for more professional performance.

Keep on capturing time...

Darrell Young