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

depth-of-field. By the same token, a lens with a maximum aperture of f/1.8 will be eas- ier to autofocus (or manually focus) than one of the same focal length with an f/4 max- imum aperture, because the f/4 lens has more depth-of-field and a dimmer view. That’s why lenses with a maximum aperture smaller than f/5.6 can give your D7000’s auto- focus system fits.

To make things even more complicated, many subjects aren’t polite enough to remain still. They move around in the frame, so that even if the D7000 is sharply focused on your main subject, it may change position and require refocusing. An intervening sub- ject may pop into the frame and pass between you and the subject you meant to pho- tograph. You (or the D7000) have to decide whether to lock focus on this new subject, or remain focused on the original subject. Finally, there are some kinds of subjects that are difficult to bring into sharp focus because they lack enough contrast to allow the D7000’s AF system (or our eyes) to lock in. Blank walls, a clear blue sky, or other sub- ject matter may make focusing difficult.

If you find all these focus factors confusing, you’re on the right track. Focus is, in fact, measured using something called a circle of confusion. An ideal image consists of zil- lions of tiny little points, which, like all points, theoretically have no height or width. There is perfect contrast between the point and its surroundings. You can think of each point as a pinpoint of light in a darkened room. When a given point is out of focus, its edges decrease in contrast and it changes from a perfect point to a tiny disc with blurry edges (remember, blur is the lack of contrast between boundaries in an image). (See Figure 5.8.)

If this blurry disc—the circle of confusion—is small enough, our eye still perceives it as a point. It’s only when the disc grows large enough that we can see it as a blur rather than a sharp point that a given point is viewed as out of focus. You can see, then, that enlarging an image, either by displaying it larger on your computer monitor or by mak- ing a large print, also enlarges the size of each circle of confusion. Moving closer to the image does the same thing. So, parts of an image that may look perfectly sharp in a

Figure 5.8

When a pin- point of light (left) goes out of focus, its blurry edges form a circle of confusion (cen- ter and right).

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

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.