Dynamic Area AF with Closest Subject Priority
All eleven AF sensors are active and the camera always attempts to focus on the closest subject. There is no user input at all on the sensor selected. The camera analyzes contrast and distance information in front of all AF sensors and will try to focus on the closest subject.
In AF-S mode, the sensor that acquires focus will light up in red briefly once focus is achieved. In AF-C mode, the focus sensor that set the focus will light up briefly immediately after the photo is taken. According to the Nikon D2X manual (p.77), "Camera may be unable to select focus area containing closest subject when telephoto lens is used or subject is poorly lit. Single Area AF is recommended in these cases". Nikon recommends this mode for erratically or rapid moving subjects when you know that the subject will be the closest object to camera.
In my tests, Dynamic Area AF with Closest Subject sometimes focused on a more distant object if it was higher in contrast. This was true whether the lens was wide angle or telephoto and it was especially true in low light situations. Group Dynamic AF (in Closest Subject Priority) would usually focus on a near lower-contrast object more reliably than Dynamic Area AF with Closest Subject. It is logical that Group Dynamic AF with Closest Subject priority would focus faster and more accurately than Dynamic Area AF with Closest Subject priority. Fewer sensors are active in Group Dynamic AF so less distance/contrast data has to be analyzed. Theoretically, using the same logic, Pattern 2 should be more responsive than Pattern 1, since fewer sensors are active.
Also in my tests, initial AF acquisition was generally faster with a user-selected AF sensor than when the camera was in Closest Subject priority. With a user-selected sensor, the camera knows which sensor to use for initial focusing; it does not have to analyze data from multiple sensors (as in Closest Subject modes) before beginning initial focusing action.
Deciding which AF Area Mode works best for particular situations requires testing under different conditions. I honestly haven't worked with the different modes enough to make definitive conclusions, but I'll share my opinions.
When speed of initial focus acquisition is the prime consideration, the camera's AF responsiveness will be faster with a user-selected sensor than a camera-selected Closest Subject sensor. So the reason to use the Closest Subject modes would be for situations with erratic action in which the camera would probably pick up the closest subject quicker than the photographer can find and center the subject on a selected sensor. One caveat, of course, is that Closest Subject priority can only be used when the subject of interest will be the closest object within the field of active sensors. Of the Closest Subject modes, Dynamic Area AF with Closest Subject would be the slowest since the camera has to analyze data from all eleven sensors before initiating AF. Group Dynamic AF with Closest Subject should be faster since fewer sensors are active, and as mentioned above, Pattern 2 should theoretically be faster than Pattern 1.
The logic gets more complicated with the user-selected modes. Is Single Area AF mode faster than Dynamic Area AF? If it isn't, why even have a Single Area AF mode—since a single initial sensor is also selected with Dynamic Area AF (and you have the added advantage of the camera predictively tracking the subject to other sensors)? If Dynamic Area AF is slower, then it must be because the other ten sensors are involved in the AF algorithms. Following the same logic, one would assume that Group Dynamic AF with Center Sensor selection is faster than Dynamic Area AF, since fewer total sensors would be involved in the AF algorithms, and that Pattern 2 would be more responsive than Pattern 1. At the present I'm not sure how much of this discussion actually involves practical vs. just theoretical differences.
*Presently I'm using Dynamic Area AF most of the time. I've compared it to Single Area AF in the field several times and can't really tell any significant difference in initial focus acquisition. With subjects moving directly toward me, I sometimes use Group Dynamic Area AF (with center sensor selection). I have been experimenting with Group Dynamic AF (with Closest Subject Priority) and Dynamic AF with Closest Subject Priority on flight shots with birds.
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