In Part 1 of this series, I provided an introduction to this autofocus evaluation, as well as a brief overview of the Canon 1D Mark IV AF system. If you have not read part 1 of this series, you can do so now by clicking here:
In Part 2 below, I provide a brief overview of the Nikon D3S AF system as it relates to sports photography concerns.
Nikon D3S AF System
The Nikon D3S features 51 total AF points, 15 of which are cross-type AF sensors. Those 15 cross-type AF sensors all reside in the center of the frame in 3 columns of 5 rows.
As with the Canon 1D Mark IV, there are a number of continuous AF customization options available for the D3S.
In Custom Setting a1, you can set the AF-C Priority Selection to give priority to shutter release, focus acquisition or a little bit of both
This mode will release the shutter when the shutter button is pressed regardless of whether AF is achieved or not. Hence, priority is given to the release of the shutter rather than the acquisition of focus.
Release + Focus Priority
This mode will also allow the D3S to capture a frame if it is not in focus; however, it will slow the frame rate in difficult focus situations to allow the camera a better chance of capturing an in-focus image.
In this mode, the D3S will only release the shutter when AF is confirmed. As a result, the frame rate may be significantly slowed at times.
AF Point Selection Modes
The D3S AF-area mode is how you select which focus point or points is used for AF. There are 3 basic modes accessible via a selector switch on the rear of the camera: Single-point AF, Dynamic-area AF, and Auto-area AF.
This is the most basic of the AF point selections. Using this mode, a single AF point is selected, which is then used exclusively for calculating AF.
The D3S uses Dynamic-area AF to help track subjects if they move off a selected AF point. The photographer still selects a single AF-point; however, the D3S will use surrounding AF points if the subject moves beyond that point of the frame. Using Custom Setting a3, the assist points can be select to include 9, 21, or all 51 AF points. Additionally, under Custom Setting a3, 51 points (3D Tracking) can be selected, which actually stores the colors in the area surrounding the active AF point in the camera for reference while tracking the subject. Dynamic-area AF is the D3S counterpart to the 1D Mark IV’s AF Point Expansion under C.Fn III-8.
This mode gives the most automated control to the camera, whereby the D3S evaluates the scene and selects the appropriate focus points. If a Nikon type D or G lens is attached, the D3S can distinguish people from other objects and will give priority to focusing on them as your subjects. In Auto-area AF, there are no visual cues for focus points when in continuous AF mode; however, in single AF mode, the active AF points will briefly appear once focus is achieved.
Focus Tracking With Lock-on
Under Custom Setting a4, the sensitivity of the AF tracking can be adjusted. As is the case with the 1D Mark IV under C.Fn III-2, there are five settings ranging between “Long” and “Short.” By default, the D3S is set to the middle, or normal, point between long and short.
The “Short” sensitivity setting allows the D3s to switch focus between objects quickly – and will shift focus even during sudden changes in distance to subject. Likewise, the “Long” sensitivity setting maintains focus for a longer period of time even if the subject leaves the frame or if another object enters the frame briefly.
Wrapping Up the D3s AF System
As with the 1D Mark IV, I have touched on the parts and points of the D3S AF system that I felt were important to me. Obviously, an exhaustive discussion of the complex AF system in the D3S could go on for much longer; however, as with its Canon counterpart, I only wish to provide an overview of the highlights of the D3S before we get into the specific performance issues.
Next in this series, we will take a closer look at some sample images from basketball games and directly compare the D3S and 1D Mark IV in specific AF situations.
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