Autofocus guide

The D7200/D7100/D7000 have a very sophisticated autofocus (AF) systems, with; 3 AF modes, 4 different AF area-modes, 51 AF points on the D7200/D7100, 39 AF points on the D7000, and 9 Custom Settings  that control AF functions. These options can be used in a multitude of combinations to achieve your specific requirements for focusing. The AF points can be used independently or together in a variety of ways, and the AF area modes used in combinations with the AF modes. On top of all that of course, you can also focus manually.

There’s a lot to learn, so let’s break it down and look at the AF modes first, followed by AF-area modes.

Autofocus

Controlling where the camera focuses is crucial to a great photo. It’s possible to let the camera choose where to focus, but of course you’re not then in control, and frequently the camera will choose to focus on something different than you want it to. Typically, it’ll focus on a person or the closest object. The best thing therefore, is for you to choose where the camera focusses, by moving the focus point to where you want to focus. Before doing that though, you need to choose an appropriate Autofocus Mode and Autofocus Area Mode, dependent on what you’re shooting; your subject, the background and situation e.g. is the subject stationary or continually moving? If it’s moving, is it moving sideways and how much, or is it also moving nearer and further from you?

Let’s take a look then at “Autofocus Modes” and “Autofocus Area Modes”.

You need to choose the most appropriate AF mode according to whether your subject is still or moving. You then choose the most appropriate  AF Area Modes, according to how many AF points you want active and how you want them to track a moving object. These two functions can be set in multiple combinations according to your needs.

AF Modes

The DSLR has 3 different AF modes:

Single-Servo AF (AF-S)

Use this mode if your subject is stationary, moving extremely slowly, or not going to move between you focusing, recomposing and shooting. In AF-S mode you are limited to choosing from 2 AF area-modes; Single-Point AF (you control the AF point) or Auto-Area-AF. I recommend you select Single-Point AF while in AF-S mode.

This mode is ideal for landscapes, still-life or traditional portraits.

Continuous-Servo AF (AF-C)

Use this mode should if your subject is moving. If you hold the shutter button half-pressed, the D7000 will continually evaluate focus distance, useful if the subject is moving nearer or further away from you. You then choose the appropriate AF area mode according to how much lateral movement you need to track, and if you want to control the focus point or let the camera do it (Auto-Area AF). I recommend you don’t select Auto-Area AF.

If your subject is hard to follow or moving laterally (left or right), set the AF-Area Mode to one of the Dynamic modes or 3D-Tracking. Use a higher number dynamic mode if there is greater lateral movement. Place your focus point over your subject and half-press the shutter, the DSLR will then follow the movement continually re-focusing.

This mode is ideal for sports, action, children/pets playing, motorsports etc.

Servo AF (AF-A)

This hybrid mode is controlled by the DSLR, which decides itself whether to switch between AF-S or AF-C. Focusing starts in AF-S mode, but if your subject moves, the DSLR switches to AF-C. You may be tempted to use this mode all the time, but if you focus and re-frame frequently, the re-framing may accidentally result in refocussing  – in which case the focus point isn’t right. So if you do focus and re-frame, use AF-S instead.

Manual Focus

There are times when manually focusing will be better than using AF. Switch the Focus Mode Selector switch from AF to M to select manual focus. Some lenses have switches too, you only need to change on the DSLR or lens – not both. If your lens has M/A and M markings then it has “full time manual focus” – which means you can manually override the AF any time – using the focus ring.

Situations where manual focus is better include for example; macro (depth of field is extremely narrow & focus point paramount), portraits (eyes must be in perfect focus), shooting through glass/wire, panning (best to pre-focus on the “shoot-point” to avoid focus lag), and low-light (when focusing is challenging & the camera may continually seek).

To enable manual focus, switch either the selector on the DSLR or the selector on the lens to M. You don’t need to put both into M.

To enable autofocus you need both switches to be set to A (or M/A if you have that).

Autofocus Area Modes

The DSLR has 4 AF Area modes that control how many AF points surround your selected AF point. In AF-C/AF-A modes these are used to track a moving subject. In AF-S mode you can only select Single-Point AF or Auto-Area AF.

Single-Point AF

In this mode only a single AF point is active. No other AF points become active if the subject moves. You’d usually use this with AF-S to focus on stationary objects, or objects that don’t change distance from you.

Look through the viewfinder and use the Multi Selector to choose the active AF point. Use the OK button to re-centre the AF point.

When selecting AF point, you will have either 11 or 51/39 points to choose from. This is set in Custom Setting a6. I’d recommend getting used to 11 first for a few months, then making a decision on the 51/39.

If you’ve chosen AF-C or AF-A, the DSLR will retain focus only if the moving subject remains behind your selected AF point. So if the subject moves closer to or further from you, the DSLR will focus, but not if your subject moves left or right – unless you move the camera or focus point. If you want the DSLR to fully track a moving subject you need to use one of the Dynamic-Area AD modes, or 3D-Tracking.

Dynamic-Area AF

In these modes you position an AF point over your subject, and if your subject moves laterally or vertically, a neighboring AF point helps maintain focus

Choose one of the below modes if you are in AF-C or AF-A modes and your subject is expected to move or moving. If your subject is moving nearer/further/laterally or you are panning – these modes are ideal.

You need to keep the shutter button half-pressed for the DSLR to achieve continuous focusing.

Note that if you lose your initial subject the DSLR may focus on a new subject, partially dependent on Custom Setting a3.

9-Point Dynamic-Area AF Since this mode only uses the neighboring AF points, it should be used if your subject is moving predictably and not too fast. People or animals walking for example.

21-Point Dynamic-Area AF Use this mode for subjects that are slightly faster and moving more unpredictably. For example players in a football or rugby match.

51/39-Point Dynamic-Area AF Use this mode for fast and very unpredictable subjects. Wildlife is a good example. (Remember, 39 points for the D7000, 51 points for the D7200/D7100).

The idea behind the Dynamic-Area modes is that you attempt to keep track on your subject by moving the DSLR to keep your subject behind your chosen AF point. If you want to keep the DSLR static and get it to change focus point as a subject passes across the viewfinder you need to use 3D-Tracking.

3D-Tracking

Use this mode if you don’t want to move/pan the DSLR to retain focus and want to keep the camera relatively still. Use it for subjects moving in any direction. The DSLR tracks subjects moving across the frame using color contrast.

Use this mode when you’re using AF-C or AF-A.

You need to position the initial AF point over your subject so that the DSLR knows what your subject is. In low-light or low-contrast situations the DSLR may struggle to retain focus and therefore this mode might not be best.

I wouldn’t recommend this mode for a sports match (football/rugby etc). If you’re focussed on one player, with the other players with the same colout shirt running about, the DSLR may well jump to these.

When would I use it? When your subject is the only object moving, or your subject has markedly different colours/contrast to other moving objects, the subject is moving latterally and nearer/further away, you have good light, and lastly good contrast. So, a single gymast performing in the floor event for example.

Auto-Area AF

The DSLR decides what to focus on automatically using all 51/39 AF points and chooses the appropriate AF point to focus. Frequently the DSLR will focus on a person or perhaps the nearest object. Either way, you are not deciding what to focus on and hence personally I wouldn’t recommend using this mode.

You might want to try it though, and may find it works fine for you. How good this mode is for you will depend on what you’re shooting and the light. If you have very good light and a prominent and/or near subject, relatively sharp contrast and a slow moving subject – you may be fine.  Ken Rockwell for example says he uses this mode most of the time and recommends using this mode.

Recently, several people  have emailed me saying that their DSLR is not focusing on their subject. A few quick emails and the cause is identified; AF-A. And yes, they’ve read Ken’s D7000 autofocus guide, but then again, look at the lighting conditions where Ken lives! That would help AF-A. Personally, I like to control what I’m focussing on.

AF Custom Settings

Now you understand AF modes, let’s look at the custom settings that control it. Your settings will vary according to what you shoot. AF settings for landscapes for example will have hugely different settings to sports shooting. So let’s have a look at these custom settings:

a1 AF-C priority selection – (Focus or Release) If exact focus is important to you, set to Focus. Otherwise, if you need to get the shot even if focus is not attained, set to Release. This setting operates in AF-C mode only.

a2 AF-S priority selection – (Focus or Release) This is similar to “a1” except it controls AF in AF-S mode. You’d normally have pretty static subjects if shooting in AF-S, so you’d want to ensure focus is obtained. You’d usually set this therefore to Focus.

a3 Focus tracking with lock-on – (1, 2, 3, 4 or 5) This controls how quickly the DSLR refocuses on a new or closer subject after losing focus. It operates in AF-C and AF-A modes. For example you focus on a giraffe that suddenly disappears behind some bushes for a few seconds. Or at a wedding, where a guest walks between you and your subject. If you want to keep focus on the giraffe or guest, set a3 to a high number – i.e. a long time before re-focusing. Alternatively, if you want the AF to quickly refocus, set to a low number (short time).

a4 (a5 on D7200) AF point illumination – (On or Off)  This controls whether or not the selected AF point is illuminated in the viewfinder. You mostly want to know where your camera is focusing, so set to On.

a5 (a6 on D7200) Focus point wrap-around – (Wrap or No wrap). This controls if the AF Point selection will “wrap around” to the other side of the screen when you reach an edge. So if you move the AF point to the edge of the display on the left, do you want it to appear on the right? I’d always set this to Wrap.

a6 (a7 on D7200) Number of focus points (AF11 or AF51/39) This controls the number of AF points that you can select in the viewfinder. It’s easier to move AF point if you only have 11 selected. The remaining AF points are still active and in use by the DSLR, you just can’t select them manually. However, you may wish to select from all 51/39. The decision is yours.

a7 (a9 on D7200) Built-in AF-assist illuminator (On or Off) Use this to enable/disable the AF assist light. Turn this Onto assist you in auto-focusing in low light, but be sure to turn it Off if you are in a museum or a church or something similar.

a8 (D7000 only) Live view/ movie AF  These settings control how the DSLR autofocuses while in Live View or recording movies.

NB: On the D7200/D7100 just press the focus-mode selector & rotate the main command dial to select.

Autofocus mode (Single-servo-AF or Full-time-servo-AF) The DSLR either focuses once, or continually – using “contrast-detection AF”. The DSLR uses difference in contrast to alter focus. There’s an excellent description here if you’d like to know more.

AF-area-mode (Face-priority AF, Wide-area AF, Normal-area AF or Subject-tracking AF). The DSLR uses one of these modes to determine where/how to focus. Select according to your subject.

f5 (f4 on D7200) Assign AE-L/AF-L button (AE/AF lock, AE lock only, AF lock only, AE lock (Hold)AF-On or  FV lock) This controls what the AE-L/AF-L button does. You may have heard of “back button focusing” – you achieve this here using AF lock only. Alternatively, you could just lock exposure – using AE Lock, continuing to use the shutter release for focusing. FV lock locks your flash value.

 

How do I access these AF Custom Settings?

Go to MENU CUSTOM SETTING MENU (pencil symbol) – a Focus

There is also one setting under f Controls.

 

In the next articles on focussing I’ll explain how to focus independently of exposure, how to compose when your AF point isn’t over your subject, techniques for better/sharper focussing, techniques for checking your depth of field, and lastly a look at the infamous back focussing issue.

In the interim, have a look at this excellent training video on Auto-focus, courtesy of Ralf’s PhotoBude: