How to Master Nikon D3, D300 Autofocus

Rude Awakening

When my D3 first arrived, I had been using a D2x for 2 years.  I never noticed the D2x’s autofocus because it worked so well.  It faded into the background of my attention.   Expecting to have the same experience with the D3, I took it out of the box and brought it with me to a friend’s wedding.   I was seated among the guests right on the aisle.  It was still daylight, so the chapel had adequate lighting.  When the bridal procession began, I expected to get some great shots for my friend, the groom.   As the procession was moving straight toward me, I had only a few seconds to get a shot.  I confidently picked up the camera, framed and pressed the shutter.  Nothing happened.  I noticed that it was in single shot mode (S on the front switch) and realized that the shutter wouldn’t trip unless the focus was spot on.  I immediately switched it to C.  My last chance.  I reeled off a few frames, but all of them were out of focus.  What had gone wrong?   Of course, I switched to manual focus, but that moment was lost.  Fortunately, I wasn’t the hired photographer that day.

To make a long story short, the problem ended up being a firmware issue which was soon fixed.  However, even though the firmware upgrade fixed 70% of the problem, I didn’t have the same degree of confidence in the D3’s autofocus as I had with the D2x.   Subjectively, the D3 hasn’t seemed to nail the focus as often as the D2x does.  This post resulted from my attempt to explore the D3’s autofocus carefully, so I can understand it and use it more effectively.  Mostly, I’m clarifying what’s in the camera’s manual with some additional observations based on my experience with it.

Three’s a Charm

On current Nikon professional cameras, such as the D3 and D300 (and D3s, D300s), there are 3 multi-position switches that affect some aspect of autofocus and what happens when you press the shutter.  These 3 switches interact with each other in surprising ways, which is why we’re discussing them together.  We’re going to try to clarify what each switch does in the context of the others, since we’ve observed a lot of confusion about these controls.  In addition, there are two push button switches that control autofocus as well, but we’ll discuss the multi switches first.

Front Switch Controls the Trigger

Nikon FRONT Switch

Nikon FRONT Switch

Let’s look at the M-S-C switch first. This is a 3-position rotary switch on the front of the camera.  It is just below the lens release button on the right, as you are looking at the camera.  It has 3 positions: M, S and C.  Lets call this the FRONT switch to avoid confusion.

You might think that M, S and C stand for Manual, Single shot and Continuous shooting.  However, these terms might not mean exactly what you expect.

M does stand for ‘manual’ focus. The M setting mechanically  disengages the focus motor from the lens, so you must focus the lens manually. In M mode, the shutter will fire whether your subject is in focus or not.  The green in-focus icon within the viewfinder can be used to tell when you’re in focus, but I find just using the image on the ground glass easier and more accurate.

S stands for ‘single servo autofocus’ according to the manual.  When the FRONT switch is set to S, the camera will fire only when the subject is in focus.  In other words, S really means ‘focus priority firing‘.  This means that the subject must be in focus before the camera will fire the shutter.  If whatever is under the focus point is not crisp, nothing will happen when you press the shutter.  This is what happened to me at the wedding.  Furthermore, if your subject is in focus, the S setting will allow the camera to fire off a burst of shots when the TOP switch is set to CL or CH.  In other words, the S on the FRONT switch does allow continuous shooting when the subject is in focus.  It is NOT restricting you to a single shot when you press the shutter.

Next on the FRONT switch, C stands for ‘continuous servo autofocus’ according to the manual.  What this really means is that the camera will fire when you press the shutter, whether the lens is in focus or not.  Now suppose that the FRONT switch is set to C and the TOP switch is set to S.  If you now hold the shutter down, you will get exactly one shot.  You will not get a continuous burst of shots.  In other words, C on the FRONT switch really means ‘trigger finger priority firing.’   It does not mean continuous firing.

C on the FRONT switch has another function associated with it.  It engages ‘predictive focus’ when you partially depress the shutter.  In other words, if the subject is moving toward or away from the camera, the focus mechanism will track its movements, keeping it in focus as it moves.  Try it by moving your finger toward and away from the lens while partially depressing the shutter button.  You’ll see that the lens refocuses as you move your finger.  In practice this improves the chances that your subject will be in focus when you do fully press the shutter to fire.

C mode on the FRONT switch can be very useful when shooting portraits.  If you position the focus sensor on the subject’s eye (using the joystick on the back), then the eye should stay in focus even if you or your subject move back and forth a little.  Just hold your finger lightly on the shutter (or the AF-ON button) and your subject will stay in focus during the flow of the shoot.  This works well with macro subjects too, where subject movements would normally cause you to lose focus from time to time.

Top Switch Controls Frames per Second

Nikon TOP Switch

Nikon TOP Switch

Next we’ll look at the S-CL-CH switch, whose functions are easier to guess from the labels. This is the switch on the top of the camera to the left of the prism (if you’re now looking down from the back of the camera. This 5-position rotary switch is labelled: S, CL, CH, Lv, Self-Timer, Mup. Let’s call this the TOP switch.

S on the TOP switch takes a single frame (picture) when you fully depress the shutter, even if you continue to hold the shutter down for a while.

CL on the TOP switch stands for ‘Continuous Low’ speed firing.  In this mode when you hold the shutter down, the camera will keep taking pictures until you let up on the shutter (or it runs out of buffer memory).  It will do this at a relatively low speed (settable via the pencil menu under ‘d2 shooting speed’).

CH on the TOP switch stands for ‘Continuous High’ speed firing.  In this mode when you hold the shutter down, the camera will keep taking pictures until you let up on the shutter (or it runs out of buffer memory).  It will do this at a relatively high speed (settable via the pencil menu under ‘d2 shooting speed’).

Lv on the TOP switch stands for ‘Live View.’  In this mode the mirror swings up and the image on the sensor appears on the rear display in real time.

Self-Timer (clock icon) on the TOP switch performs the traditional self-timer function.   You can set the delay in the menu denoted by the pencil icon (under ‘c Timers/AE lock’ –> ‘c3 Self-Timer delay’).

Mup on the TOP switch stands for ‘Mirror Up.’  When you press the shutter once, the mirror swings up, but no picture is taken.  When you press the shutter a second time, the picture is taken and the mirror swings back down.  This is extremely useful for macro or telephoto shots where you want to minimize camera vibrations to get the sharpest possible picture.  The mirror slapping against the bottom of the prism mount causes significant vibration.  So, you want to provide a delay after the mirror slaps before you take the picture.  A second or two is enough. This is a great  option when you don’t happen to have a cable release with you.

Back Switch Creates Confusion

Nikon BACK Switch

Nikon BACK Switch

Finally, there’s another 3-position rotary switch on the back with three icons enclosed in brackets. These icons are  (1) a white rectangle, (2) a set of brackets with 4 dots around them, and (3) just a set of brackets inside larger brackets. Let’s call this the BACK switch.

On the BACK switch there are the 3 settings, which are for

  • (1) ‘Single point autofocus‘       (the bottom position – brackets within brackets),
  • (2) ‘Dynamic area auto focus‘ (the middle position – brackets with 4 dots), and
  • (3) ‘Auto area autofocus‘          (the top position –  white rectangle inside brackets).

Here’s what each of these settings does.

  • (1) Single point autofocus is for relatively static subjects where a single fixed focus point is best.  The focus point is selected by the photographer using the joystick. The focus point appears as a red rectangle in the viewfinder.  This is manual focus point selection, which remains fixed unless you manually change it via the joystick.
  • (2) Dynamic area autofocus is for situations where the subject may move away from the initial focus point, which you’ve selected, and you want the camera to keep the subject in focus as it moves.  In other words, you tell the camera where the subject is (at first) by selecting the focus point.  The camera ‘remembers’ what’s on the focus point, and estimates its trajectory.  If the subject moves, the camera looks for it under one of the other focus points, looking first on its trajectory.  Here’s where things get complicated with many different subcases:
    • (a) FRONT switch is set to S (focus priority). Camera focuses on subject in selected focus point only.  That is, no dynamic area autofocus. Surprised?
    • (b) FRONT switch is set to C (trigger finger priority).  Here you do get dynamic area autofocus.  There are several cases depending on menu settings.
      • (i) In the pencil menu, custom setting ‘a3 Dynamic area AF’ must be set to either 9, 21 or 51 focus points (but not the 3D setting).  You select a focus point manually (with the joystick). How you choose from 9, 21 or 51 focus points depends on the amount of movement you expect.
        • For runners and bicycles Nikon recommends 9 focus points. Things moving predictably and not fast.
        • For football, Nikon recommends 21 focus points.  Things moving unpredictably.
        • For birds, Nikon recommends 51 focus points. Things moving quickly and are not easily framed.

        If subject moves out of the selected focus point, the other 8, 20, or 50 focus points will be searched to find the subject and maintain focus.

      • (ii) In the pencil menu, custom setting ‘a3 Dynamic area AF’ is set to ‘3D  51 points (3D-tracking)’. If the subject leaves the selected focus point, the camera will use 3D tracking with all 51 points to search for the subject and refocus.  This is useful for objects that are moving erratically from side to side in the frame, such as tennis players. 3D focus tracking uses color to help identify the subject and track it.  It won’t work if everything in the scene is the same or similar colors.  However, it’s quite amazing to watch it work as you move your finger in front of any lens that can focus closely.  The little red focus points light up and follow your finger.  Guess I’m easily amused.
  • (3) Auto area autofocus uses all 51 focus points and identifies where the subject is.  In other words, you don’t give the camera a clue about what the subject is or where it is in the frame.  The camera guesses, perhaps based on some kind of scene analysis. Nikon hints at this in the manual where they say that with a G or D lens, the camera “can distinguish human subjects from the background.”  Unfortunately, Nikon doesn’t say any more about how their algorithm works.  Though after exploring it a little bit, I’ve noticed that it seems to favor strong edges in the center of the field of view.  It may also favor objects closer to the camera, but this is a guess on my part. Fortunately, the camera highlights the focus points in red that were used to find focus when the FRONT switch is set to S (Single).  So, you can see where it’s focusing and correct it if necessary.  I’ve found this mode works well for human faces in studio environments, where you’ve got a simple, uncluttered background.  It locks in on facial features, such as eyes, lips and sometimes the nose.  Curiously, every time you lightly tap on the shutter button, it locks onto slightly different features.  So, focus may vary.  It’s best to experiment with this to see if you like it before using it with a paying client. All things considered, for portrait shooting I still prefer to use a single autofocus point on one of the subject’s eyes.  This rarely fails to nail the focus.

Auto Area Autofocus showing focus points determined by camera

Auto Area Autofocus showing focus points determined by camera

AF-ON and AF-L Buttons

There are two more buttons on the back of the camera that need to be mentioned. First is the AF-ON button.  On the D3, there are two of them (the second one is on the vertical grip). The AF-ON button initiates autofocus by default.  It can be reprogrammed in the pencil menu under ‘a9 AF-ON button’ and ‘a10 Vertical AF-ON button’ which can be programmed independently.

The AE-L/AF-L button duplicates the half shutter press.  It locks both the exposure and the focus until released.  It can be reprogrammed in the pencil menu under ‘f6 Assign AE-L/AF-L button.’

My Settings

For stationary subjects, I use ‘S’ on the FRONT switch and ‘Single point autofocus‘ on the BACK switch. I often use this for portraits if I’m expecting the subject not to move around too much.  I also use ‘S’ on the top switch in studio environments, since strobes need time to recycle.

For portraits of children, pets or anyone who may be moving in the frame (dancers and actors) a bit, I use ‘C’ on the FRONT switch and either ‘Single point autofocus‘ on the BACK switch or ‘Dynamic Area autofocus‘ on the BACK with 21 focus points.

For moving subjects, I use ‘C’ on the FRONT switch and ‘Dyamic area autofocus‘ on the BACK switch with 21 focus points, or sometimes 51 focus points.  I don’t usually shoot wildly erractic subjects, though I do shoot birds and butterflies.

I also like to do HDR (High Dynamic Range) panoramas.  For these, I always focus manually and use exposure bracketing with the TOP switch set to CH.   It’s amazing how fast a D3 can take a few hundred frames on an automated panoramic head.


I hope this helps you to better understand Nikon’s autofocus system in its current incarnation.  You are encouraged to go out and experiment with it.  It may at first seem to be an untamable beast.  And I still find it a little more finicky than the D2x.  But it can do some amazing things.

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