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Manual Control Options
The Sony α (alpha) A100 offers full manual control of exposure, white balance, ISO and focus, plus a range of image parameters. Not everything that is possible is convenient on the A100, but it's all there. For instance, users must change the parameter dial on the top left of the camera while pushing the button in its center, while also navigating with the four-way control and looking at the LCD screen. This is not easy, and is a little disappointing since manual control should be a DSLR’s bread and butter. The Sony A100’s mode dial offers manual exposure, aperture priority, shutter priority and program modes.
Focus
Auto Focus (7.75)
The 9 auto focus points in the Sony alpha A100's viewfinder are clustered toward the center of the frame. One is dead center. Four more are arrayed at 12, 3, 6 and 9 o'clock, but all these are also close to the center. Farther out, the last four mark the corners of a rectangle that covers about the middle third of the frame. The 4-way controller can be used to select the active point with a single click. Hit the upper left segment of the controller, and the upper left point is activated. Hit the center button, and the center point is active.
The Sony A100's focus is accurate but slow in bright light. In subdued light, it slowed a bit more. Low-light performance has been improving in DSLRs over the years, so the A100 looks better than older entry-level cameras. It doesn't perform as well as the Nikon D80, which is also new, though about $250 more.
Manual Focus (6.5)
The Sony alpha A100's viewfinder is dark and small, and we found it hard to focus manually. Subjects simply don't snap into focus on the screen. We didn't encounter a situation where manual focus was better than auto focus.
Exposure (8.5)
The Sony α (alpha) DSLR-A100 has an exposure lock function which allows the user to freeze an exposure setting in automated modes, and an exposure compensation control that allows the user to bias exposure 2 EV above or below the meter reading, in 1/3 EV steps. The lock function is unusually flexible. It can be set to take a spot reading and lock on that, or to lock on the current meter pattern's reading. The lock button can also be set to hold the reading only as long as it is pressed, or to hold it until it is pressed a second time.
Metering (9.0)
The Sony alpha A100 offers three metering patterns: spot, center-weighted average and evaluative. Spot reads a small section of the image, and can be set so that the spot coincides with the active auto focus point. Center-weighted average takes a reading that encompasses the whole frame, but is most sensitive to the middle of the image. Evaluative takes readings in 40 segments across the frame, and computes an exposure setting. The evaluative setting is supposed to detect backlighting and other difficult metering situations and compensate for them. In our tests, the A100's evaluative system worked much better than competing systems. The A100 uses evaluative metering in its automatic modes, and should deliver good results in a wide range of situations.
White Balance (7.25)
The Sony α (alpha) DSLR-A100 offers a full range of white balance controls: it has presets for daylight, shade, overcast, tungsten, fluorescent and flash. It allows Kelvin color temperatures to be set, it can create a custom white balance, and it can set white balance automatically.
The usefulness of a single setting for fluorescent lighting is questionable – fluorescent tubes vary significantly from type to type. In our test, the A100's preset was too blue. When the A100 is set to a specific Kelvin temperature, it allows the option of manually shifting color toward green or magenta as well. It's a useful feature, but it would be even better if it were available in all the white balance modes rather than in only the custom setting.
ISO (7.5)
The Sony α (alpha) A100 offers ISO settings in full stops from 100 to 1600. Competing cameras offer ISO settings in 1/3 EV increments, a feature that's helpful in limiting noise – there is usually a significant increase in image noise with every step in ISO. So, if ISO 800 isn't fast enough, it pays to try ISO 1000 and 1250 before 1600, if the camera allows it (the Sony A100 doesn’t, unfortunately). Check out the Noise sections in the Testing / Performance portion of this review to see how the ISO settings will affect the overall image quality.
The A100 has two extra ISO settings: Lo80 is an ISO 80 equivalent that is meant for shooting low-key images (subjects that are supposed to look dark in the final picture). Hi200 is meant for high-key images (for pale subjects). Our dynamic range test didn't detect a significant effect from these settings.
Aperture (0.0)
The Sony A100 can set f/stops in 1/3-EV increments via the control dial. The kit lens has a maximum aperture of f/3.5 at 18mm and f/5.6 at 70mm. The minimum apertures are f/22-f/36, respectively. Most users would benefit from having a faster lens for available light use. While the most common second lens to buy is a telephoto zoom, a 35mm or 50mm f/2.0 would broaden the capability of the A100 at least as much.
Shutter Speed (7.75)
The A100's shutter speed range runs from 30 seconds to 1/4000th of a second, plus a Bulb setting for even longer exposures. Speeds can be set in 1/3 EV increments. There's no practical reason for a wider range of settings. At the fast end, 1/4000th allows an exposure of f/2.0 at ISO 100 in full daylight. At the slow end, timing exposures with a stopwatch is perfectly adequate for anything over 30 seconds.
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