When Nikon first began development of the Live View feature for the D3 and D300, we considered how to provide the best possible system for all genres of professional photographers.
When shooting moving subjects, as in sports, portraits or snapshots, subject detection speed is given the highest priority, while accuracy is also important. Phase-detection AF is useful for quickly capturing moving subjects. The Multi-CAM 3500FX/DX autofocus sensor module with 51 focus points, used on the D3 and D300, employs this phase-detection method.
Another autofocus method is contrast-detect AF, which analyzes data from the image sensor and drives the lens as it searches for the lens focus position that has the highest contrast in the image. This method takes longer to focus than the phase-detection method, and is therefore not suitable for capturing moving subjects. It is, however, particularly advantageous for high-precision focusing. With digital SLR photography, photographers usually check the focus by enlarging an image on a computer monitor, thereby requiring a completely different level of focusing precision. This is particularly true for studio still lifes and landscape photography that demands extra-precise focusing. The contrast-detect method is ideal for such situations.
In the D3 and D300, Live View includes both of these AF methods. The Live View Hand-held mode for composing an image without looking through the viewfinder uses the phase-detection Multi-CAM 3500FX/DX autofocus sensor module. On the other hand, the Live View Tripod mode for studio photography, which requires accurate focus, uses image data directly from the image sensor for contrast-detect autofocus. Using these AF methods increases the value of the Live View function for a wide range of photography genres.
By using the Auto-area AF mode to shoot people, subject identification information from the Scene Recognition System, which recognizes people separately from the image background, is used to enable the camera to automatically select the focus point and selectively focus on that person. This allows you to concentrate on composing the image while leaving selection of the focus point up to the camera.
In order to maximize the usefulness of high-precision contrast-detect autofocus for professional photographers, two areas must be adequately addressed. The first is the number of lenses compatible with autofocus precision improvement, and the second is the size of the autofocus area used.
To improve precision, the D3 and D300 use an integrated contrast-detect autofocus filter closely tuned with the image-processing engine. Hardware is used to perform part of the processing, with the aim of speeding up processing. Contrast-detect AF drives the lens to find the best focus, and this lens drive control varies with each lens. Nikon has gone through a process of trial and error to enable as many NIKKOR lens types as possible to achieve high-precision focusing through optimum drive control. This lets photographers use their favorite lenses in their work for greater freedom. We’ve developed the optimum drive control for each lens to assure precision with the entire range of AF-S NIKKOR lenses.
Expanding the autofocus area is another essential requirement for improving its utility for professionals. Manual focusing has become the norm for still-life photography in the studio environment. One of the reasons for this is the limited focus area coverage on the monitor when using conventional phase-detection autofocus.
The contrast-detect AF used on the D3 and D300 models removes these limitations and permits focusing on any area of the image sensor.
With the D3, Live View photography is possible at any aperture setting from maximum to minimum, and the aperture can be changed during shooting while confirming the depth of field. Exposure can also be checked in real time. Since both the D3 and D300 feature a large 3-inch high-resolution VGA LCD monitor with approximately 920,000-dot resolution, the target subject can be enlarged and the focus confirmed in real time.
