136 David Busch’s Nikon D7000 Guide to Digital SLR Photography

quickly and precisely snap the image into sharp focus and line up the vertical lines, as shown in Figure 5.3. Of course, this scenario—vertical lines being interpreted by a hor- izontally oriented sensor—is ideal. When the same sensor is asked to measure focus for, say, horizontal lines that don’t split up quite so conveniently, or, in the worst case, sub- jects such as the sky (which may have neither vertical nor horizontal lines), focus can slow down drastically, or even become impossible.

Phase Detection is the normal mode used by the D7000. As with any rangefinder-like function, accuracy is better when the “base length” between the two images is larger. (Think back to your high-school trigonometry; you could calculate a distance more accurately when the separation between the two points where the angles were measured was greater.) For that reason, Phase Detection autofocus is more accurate with larger (wider) lens openings—especially those with maximum f/stops of f/2.8 or better—than with smaller lens openings, and may not work at all when the f/stop is smaller than f/5.6. As I noted, the D7000 is able to perform these comparisons very quickly.

Improved Cross-Type Focus Point

One improvement that Nikon D7000 owners sometimes overlook is the upgrade to a cross-type focus point at 9 of the 39 center positions. Why is this important? It helps to take a closer look at the Phase Detection system when presented with a non-ideal subject.

Figure 5.4 shows the same weathered wood pictured earlier, except in this case we’ve chosen to rotate the camera 90 degrees (say, because we want a vertically oriented com- position). In the illustration, the image within the focus sensor’s area is split in two and displaced slightly side-to-side, but the amount and direction of the misalignment is far from obvious. A horizontally oriented focus sensor will be forced to look for less obvi- ous vertical lines to match up. Our best-case subject has been transformed into a worst- -case subject for a horizontal focus sensor.

The value of the cross-type focus sensor, which can interpret contrast in both horizon- tal and vertical directions, can be seen in Figure 5.5. The horizontal lines are still giv- ing the horizontal portion of the cross sensor fits, but the vertical bar can easily split and align the subject to achieve optimum focus. Cross-type sensors can handle hori- zontal and vertical lines with equal aplomb and, if you think about it, lines at any diag- onal angle as well. In lower light levels, with subjects that were moving, or with subjects that have no pattern and less contrast to begin with, the cross-type sensor not only works faster but can focus subjects that a horizontal- or vertical-only sensor can’t handle at all.

So, you can see that having a center cross-type focus sensor that is extra-sensitive with faster lenses is a definite advantage. The location of the D7000’s cross-type focus sen- sors is shown in Figure 5.6.

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Nikon D7000 manual Improved Cross-Type Focus Point

D7000 specifications

The Nikon D7000 is a mid-range digital single-lens reflex (DSLR) camera that has garnered a reputation for its impressive blend of features and user-friendly design. Released in 2010, the D7000 marked a significant step forward for Nikon, appealing to both amateur photographers and enthusiasts seeking a robust and versatile camera.

At the heart of the D7000 is a 16.2-megapixel APS-C (DX) CMOS sensor that delivers sharp, high-resolution images with rich colors and stunning detail. Coupled with Nikon's EXPEED 2 image processing engine, the camera excels in low-light performance, allowing photographers to shoot at sensitivities ranging from ISO 100 to ISO 6400, expandable to ISO 25600. This flexibility empowers users to capture clean images even in challenging lighting situations.

The autofocus system of the D7000 is another highlight, featuring a 39-point AF system with nine cross-type sensors. This advanced system ensures fast and accurate focus, making it suitable for a variety of shooting scenarios, from portraits to fast-action sports photography. The camera also includes full HD video recording capabilities at 1080p, with options for frame rates of 24, 25, and 30 frames per second, providing videographers with quality and flexibility.

The D7000's build quality is robust, with a magnesium alloy body designed to withstand the rigors of regular use. It is weather-sealed to protect against dust and moisture, making it a reliable choice for outdoor shooting. The camera features a 3-inch LCD screen with a resolution of 921,000 dots, allowing for high-clarity image review and menu navigation. The 100% viewfinder coverage gives a true-to-life perspective when composing shots.

Additional features include in-camera HDR, multiple exposure capabilities, and a comprehensive set of scene modes that assist users in achieving the best results in various conditions. The D7000 is also equipped with dual memory card slots, supporting both SD and SDHC formats for ample storage and backup options.

With its combination of high-quality imaging, advanced autofocus, robust build, and versatile features, the Nikon D7000 stands out as a powerful tool for photographers looking to elevate their craft.