Minolta DiMAGE F100Minolta builds a compact, stylish 4 Megapixel model with sophisticated autofocus.<<Viewfinder :(Previous) | (Next): Exposure & Flash>> Page 5:OpticsReview First Posted: 04/18/2002, Updated: 05/29/2003 |
Optics
The
F100 is equipped with a 3x Minolta GT, 7.8-23.4mm lens, the equivalent of a
38-114mm lens on a 35mm camera. A shutter-like lens cover automatically moves
in and out of place when the camera is powered on or off, eliminating the need
for a removable lens cap. When the camera powers on, the lens telescopes outward
about two inches into its operating position, retracting again when the camera
is shut off (or after the camera has been left in Playback mode for a while).
Aperture ranges from f/2.8 to f/8.0 (the actual maximum lens aperture depends
on the lens focal length, varying from f/2.8 at wide angle to f/4.7 at telephoto),
and can be manually or automatically controlled. Focus also features either
manual and automatic control, and ranges from 1.6 feet (0.5 meters) to infinity
in normal mode. A distance readout appears on the LCD monitor in manual focus
mode, with the actual focus distance controlled by the up and down arrows of
the Four Way Arrow pad (pressing the center of the pad switches the up and down
arrows back to controlling the zoom lens). Macro mode changes the focus range
for closer, smaller objects, focusing from 0.7 to 2.0 feet (0.2 to 0.6 meters).
The 20 cm minimum focusing distance doesn't sound all that close, as many cameras
focus much closer than this. The F100's lens operates in telephoto mode when
macro focusing though (most cameras force you to wide angle), so the net result
is somewhat better than average macro shooting, with a nice working distance
that helps the flash work well too. The minimum macro area I measured for the
Dimage F100 was a very respectable 2.3 x 1.8 inches (59 x 44 mm).
In addition to the F100's 3x optical zoom, the camera also features as much as 2.5x digital zoom (enabled through the settings menu). As always, I feel a need to remind readers that digital zoom compromises image quality because it only crops out and enlarges the central portion of the CCD image. Thus, it trades off resolution directly for magnification, the more you enlarge the image digitally, the softer it gets. (Digital zoom is useful though, when you're shooting at a lower resolution setting to begin with - with its 2272 x 1704 pixel CCD, the F100 can deliver the full 2.5x digital magnification with no loss of quality when you're shooting 640 x 480 images.)
The F100 offers a few unique AF options, including Single Shot, Manual, Full-time AF, and a sophisticated Subject Tracking system, some of which use Minolta's new Area AF system to automatically detect the subject. The camera's large central autofocus area (indicated by a set of white brackets on the LCD screen) is made up of five separate AF regions, arranged dead center, and above, below, left and right of center. When you press the shutter button halfway, one of these five regions will lock onto the subject. When in Auto mode, the focus "box" selected by the camera illuminates in red, and you can watch it track the subject as you move the camera around. Tracking AF is also available as an option when the camera is in Manual mode, but the "focus box" doesn't appear on the LCD screen. (This may be because the model I tested to write this review was only a prototype. I'll update the information here after I've had a chance to test a production model.)
In
Single-Shot mode, the camera simply locks focus when the Shutter button is half
pressed, basing focus on one of the five focus areas. You can specify one of
the five focus areas as the only active area by pressing and holding the center
button of the Four Way Arrow pad. This displays the AF Area selection screen,
where you can use the arrow keys to select a focus area and then press the center
of the arrow pad again to confirm the selection. The camera will then base its
focusing only on that AF area. In Full-time AF mode, the F100 continuously adjusts
the focus, rather than waiting for you to half-press the Shutter button.
I mentioned Manual focus mode above, noting that a distance scale appears on the LCD screen to help you gauge focus. The up/down arrow keys alternate between focus and zoom lens operation when you press the button in the middle of the In addition to the distance scale, the F100 zooms the LCD display by about 2x whenever you adjust the focus manually, as an aid to telling when you've achieved correct focus.
A major new feature of the F100 is Minolta's Subject Tracking AF, which made its debut on several of Minolta's film cameras a little while ago. Subject Tracking AF works with all five AF Areas, locking a moving subject to one of the frames, and then "handing it off" to an adjacent frame as it moves. This should be great for catching shots of an active toddler or a child's first little league game, as you just have to worry about keeping the subject somewhere near the middle of the frame, not whether or not focus is set. For best results, frame the subject in the focus brackets that appear on the LCD display, and halfway press (and hold) the Shutter button. As the subject moves, the active AF area will appear in red. The AF tracking isn't lightning fast, but Minolta says it's sufficient to track a subject moving at 9mph (14.5 km/h) toward or away from the camera, or 3.4 mph (5.4 km/h) from left to right, at a distance of 12 ft (3.5m) at the wide angle lens position, or 33 ft (10m) at the telephoto position. To translate this to the real world, 9 mph is about the speed of a child running, (well, a small child, anyway) while 3.4 mph corresponds to a brisk walk. The tracking ability is more effective with the lens at its wide angle position than at telephoto, and also benefits from plenty of light and a contrasted subject. It appeared to work pretty well in actual use though, and seems like a useful camera feature for most users.
I mentioned Minolta's "intelligent" AF system that supposedly can recognize and focus on people in preference to background objects. I had a hard time confirming that this was the case, as opposed to the camera simply selecting the closest object in its field of view. It did in some cases seem to show a tendency to focus on people's heads, though I found that it could easily become confused in low contrast situations, or if there was a bright object (a CRT, for example) in the frame with the subject. Also, if I moved the camera too rapidly, the tracking system would lose its "lock" on the subject and possibly end up acquiring a different element in the scene as its "subject." Despite its limitations though, I thought that the F100's intelligent autofocus capabilities were a significant step forward for consumer digicams.
Like other Minolta GT lenses I've tested recently, the one on the Dimage F100 seems to be of unusually high quality for a consumer digicam. It's very sharp across the frame, with little or none of the corner softness I've come to expect from consumer-level digicam lenses. It also shows almost no chromatic aberration, another common consumer lens failing. It did have higher than average barrel distortion at its wide angle setting, about 1.05 percent. (Most digicams show 0.8% or less barrel distortion, and amount I still consider too high.) I also found the zoom control rather slow to operate, it taking s good four seconds to rack from telephoto back to wide angle. On the plus side though, the F100's lens provided pretty fine-grained zoom control, with fairly small steps between its "preferred" focal length positions. (As near as I can tell, the F100's lens has about 13 actual focal length steps along its zoom range, more than most cameras I've tested.)
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