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Nikon D100

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Page 5:Optics

Review First Posted: 5/31/2002

Like other Nikon SLRs, the D100 accommodates a wide range of Nikkor lenses, via the standard Nikon "F" lens mount. The D100's lens mount includes both mechanical AF coupling for older lenses, and AF electrical contacts for the latest AF-IF or AF-S Nikkor lenses with internal focus motors. With very few exceptions, you can use the D100 with any F Mount Nikkor lens ever made. (Actually, I'm not personally aware of any F-mount lenses that flat-out *wouldn't* work, but do know that some of the really unusual Nikkor lenses from the past [full-frame fisheye lenses?] had problems on some camera bodies, requiring mirror lockup to function properly. This is a vanishingly small percentage of the possible lenses that could be used with the camera though, so you can safely assume that most any F mount lens in your camera bag will work just fine with the D100.)

Functions and exposure modes available with a given lens will vary greatly with the lens type. More recent Nikkors (the G- or D-type models) include a microchip that communicates focal-distance information to the camera. Lenses without the microchip won't support the 3D Matrix metering mode. Here's a table giving a brief idea of the functionality available with different Nikkor lens types (abstracted from the D100's manual, used by courtesy of Nikon USA, Inc).


Given that the optical characteristics will depend entirely on the lens attached, I'll instead concentrate here on the focusing options and modes. There's a lot to talk about, given the exceptional control and flexibility afforded by the D100's autofocus systems. The D100 lets you take advantage of auto or manual focus via a small dial on the front of the camera, next to the lens. Setting the switch to "M" puts the camera into manual focus mode, "S" places it in Single Servo AF (focus priority), and "C" puts it into Continuous Servo AF (release priority). Single Servo simply means that the camera sets focus only once, when the Shutter button is first pressed halfway, and is best for still objects. Continuous Servo means that the camera continuously adjusts the focus, as long as the Shutter button is halfway pressed, and is best for moving objects.

There's an important difference between Single and Continuous Servo modes: In Single Servo mode, the shutter won't release unless the lens is focused. (Focus Priority) In Continuous Servo mode however, the camera will fire regardless of the state of focus. (Release Priority) If you want to be sure that the camera is focused when you snap the picture, use Single Servo mode. Use Continuous Servo for moving subjects, and/or times when the instant of shutter release is more important to you than sharp focus.

The AF Area Mode option on the Mode dial lets you select between Single Area and Dynamic Area by turning the Main Command dial, both of which offer a Closest Subject Priority option. Single Area AF simply means that the camera judges focus based on one part of the subject. Dynamic AF employs all five of the autofocus brackets, or areas. When Dynamic Area focusing is enabled, the camera first focuses on the subject in the central focus area. When the subject moves to a different AF area, the camera shifts the focus to "follow" the subject. This is great for irregularly moving subjects. (Sports and kids come to mind.) The Closest Subject Priority option (enabled through the Custom Settings menu) means that the camera first focuses on the closest object that falls into one of the five focus areas and then tracks it as it moves. (Note that no focus area brackets are illuminated in the viewfinder with this mode and that this mode doesn't work well with telephoto lenses or poorly lit subjects, according to Nikon). In Single Area AF mode, you can change the primary focus area by unlocking the focus area selector (the Four-Way Arrow pad on the back panel) and then shifting the focus area using the up, down, right, or left arrow keys. You can lock the focus area selection by turning the switch back to the lock position. By default, the D100 does not "wrap" the focus area selector as you scroll between focus areas. Through the Custom Settings menu though, you can opt for a "Wrap" function. What this means is that if you press the right arrow key again, after the right focus area is already selected, the selection will immediately jump to the left focus area. The same thing happens when moving the focus area selection vertically as well.

There are two methods by which you can lock focus on the D100. The first is to half-press the shutter button to lock the focus, placing your subject in the selected focus area, halfway pressing the Shutter button, then realigning the composition and firing the shutter. (This is the default behavior of the shutter button, but it can be disabled. - Unlike most cameras, you can choose whether or not the shutter button also locks exposure, via an option on the Custom Settings menu.) Alternatively, when using Single Servo AF, you can press the AF-L/AE-L button to lock focus (and exposure, unless the button is set for focus only in the Custom Settings menu). Keeping this button pressed will lock focus and/or exposure, even if the Shutter button is released. This lets you recompose the photograph without keeping your finger on the Shutter button, but on the AE-L/AF-L button instead. (Reducing the chance that you'll accidentally trip the shutter when you don't intend to.)

There are several options available for the AE-L/AF-L button, which can be set via Custom Settings Menu 14. You can program it to lock either focus or exposure separately, or both together (the default). You can also change its operation so a single press locks and holds the exposure setting. (No need to keep the button pressed down.) Finally, you can set the AE/AF lock button so it alone controls the autofocus system, meaning the autofocus won't actuate when the shutter button is half-pressed, only when the AE/AF lock button is pressed instead.

Autofocus Speed
I mention AF speed because it's the topic of frequent questions from my readers, although I confess to having no quantitative way to measure it. I'm also hampered somewhat in my assessment by not having other D-SLRs close at hand to do direct comparisons with. I also need to point out that AF speed will vary greatly with the lens being used. All that said, the D100's AF speed struck me as merely average. I did most of my shooting with Nikon's 24-85mm f/3.5-4.5 G-series AF-S Nikkor lens. This is one of their "silent" AF lenses, with an internal motor, and as such is a fairly fast-operating lens. Switching rapidly between distant subjects and ones near the closest focusing distance, my subjective sense was that it took about a half-second to achieve focus. Traversing smaller distances, the focus lock was much faster. With a moving subject (Charlotte the Wonder Dog), and the camera set in Continuous Servo focusing mode, I felt that the camera was consistently lagging the subject a bit. This was an entirely unscientific test, but I was left with the distinct impression that the lens/camera combination could have been faster. (I'd guess that she was moving about 12-15 mph towards me, at a distance of around 20 feet when I was snapping the picture. - The most sharply-focused area seemed to be a couple of feet behind her under those conditions.) I didn't have one at hand to compare with the D100, but my recollection was that the D1X/H models could track action better, even though the D100 showed lower autofocus-derived shutter lag in my static tests.

Confused by Apertures and Depth of Field? - Do you know how to use "Front Focus" or "Back Focus" to get *all* your subject in focus? Visit our free Photo Lessons area and click on the lessons "Focusing Up Close" and "Selective Focusing Outside!"

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