Minolta Dimage 5The "little brother" to the Dimage 7 - same great features, but 3.3 megapixels and a (much) lower price...<<Viewfinder :(Previous) | (Next): Exposure & Flash>> Page 5:OpticsReview First Posted: 9/14/2001 |
OpticsThe Dimage 5 is equipped with a 7.2-50.8mm, aspherical glass lens, the equivalent of a 35-250mm lens on a 35mm camera. Although they have the same lens, the range is slightly longer than on the Dimage 7 (28-200mm) because of the smaller chip size on the Dimage 5. Unlike most digicams we've worked with, the lens zoom operates by rotating a collar around the lens barrel, which is coupled mechanically to the lens elements themselves. We like the sure, precise control this gives, as opposed to the rocker switch-controlled motor that most digital cameras use to rack the lens in or out. It definitely requires two hands, but the direct manual control will feel great to photographers accustomed to film-based SLRs.
The lens is made up of 16 elements in 13 groups, including two AD glass elements and two aspherical surfaces. Aperture is manually or automatically controlled, with a maximum setting of f/2.8 at wide angle and f/3.5 at telephoto. Focus ranges from 1.6 feet (0.5 meters) to infinity in normal mode. Activated by a small switch on the lens barrel, a macro focusing mode allows you to focus on objects 5-19 inches (13-48cm) from the lens surface. A mechanical interlock prevents the Macro mode switch from being thrown unless the camera is at maximum telephoto. The minimum macro area covered at the closest focus distance is a fairly small 1.93 x 1.44 inches (48.9 x 36.7 mm). A plastic lens cap with spring-loaded catches hooks onto the inside lip of the lens, protecting it from dirt and scratches. The lens cap does not have an eyelet for attaching a strap, so you'll want to take extra precautions not to lose it.
The Dimage 5 provides both manual and automatic focus control. The camera's specification sheet describes the autofocus system as a "Video AF system." While we're not familiar with that terminology, conversations with Minolta engineers at PMA revealed that the Dimage 5 uses a phase-detection focusing technology rather than the much more common contrast-detection system. The advantage of the more complex phase-detect approach is that the camera not only determines whether or not the lens is in focus, but also how far out of focus it is, and in which direction (near or far). With this information, the camera can focus much more quickly, since it "knows" roughly how much, and in which direction, to adjust the focus, rather than having to "hunt" for the best focus at the outset. The AF system will still have to do some hunting for the best setting, but it should spend less time doing so than a contrast-based system.
In practice, we've found that Minolta's autofocus technology is neither more nor less effective than the schemes used on other cameras, but is definitely different in what it'll focus on and what will give it problems. We've seen the Minolta cameras sometimes have trouble focusing even when the subject contained sharply contrasting detail, which would be an ideal target for conventional contrast-detect autofocus systems. On the other hand, we've seen the Dimage cameras focus very well with low-contrast, lightly textured subjects that would give normal autofocus fits. The final chapter on digicam autofocus technology clearly isn't written yet, and in the real world, Minolta's phase-detect AF appears to be just a different approach, without overwhelming strengths or weaknesses.
For what it's worth, we found the autofocus of the Dimage 5 under good conditions to be a bit faster than average among cameras we've tested, and noticeably faster than that of the Dimage 7. We're not sure of the reason for this (given the two cameras' identical electronics and optics), but speculate that it might have to do with the smaller amount of data the system has to deal with, thanks to the Dimage 5's smaller CCD.
The Dimage 5's
autofocus system offers both Single-Shot and Continuous AF settings. In Single-Shot
AF, the camera only sets the focus when the Shutter button is halfway depressed.
In Continuous AF mode, it adjusts focus continuously, which is an enormous drain
on battery power. You can switch to Manual Focus by pressing the AF / MF button
on the camera's left side. In Manual Focus mode, you focus by turning a ribbed
ring around the base of the lens barrel. As you focus, the distance is displayed
in meters or feet at the bottom of the LCD monitor (or EVF) under the MF icon.
The camera also provides adjustable autofocus areas. Wide Focus area, indicated by a wide set of brackets in the viewfinder image, bases its focus on the most prominent subject detail in the center of the frame, which is determined by an array of local focus areas working together. When the focus is locked in single AF mode, one of the AF sensors (in the form of a small rectangle) will briefly flash on screen to indicated the point of focus. This mode is particularly effective when shooting a moving subject. Spot Focus Point, indicated by a target crosshair in the center of the frame, bases its focus on one specific spot in the viewfinder. By pressing and holding down the center of the Five-Way Arrow controller pad, you can switch between Wide Area and Spot Point autofocusing modes. If you release the controller pad when the Spot AF target is displayed, you can then use the four arrow buttons to move the focus point to anywhere within the frame -- a feature known as Flex Focus Point AF. (See the screen shot at right (actually from the Dimage 7), in which we switch from Wide Area to Spot Focus, and then move the Flex Focus Point around the screen.)
An AF / AE Lock button, located in the upper right corner of the back panel (below the Mode Dial), allows you to lock the focus for a specific portion of the frame, without having to hold down the Shutter button halfway. In default mode, pressing this button also locks exposure, but you can configure it in the Custom 1 Record menu to switch between AF / AE Hold, AF / AE Toggle, AE Hold, or AE Toggle functions.
In addition to the optical zoom, the Dimage 5 also offers a 2x Magnification button, located at the very bottom of the back panel, on the right side. Pressing this button activates an instant 2x digital zoom, which magnifies the image electronically and displays an "X2.0" symbol in the monitor. When activated, the live image on the LCD monitor is enlarged by 2x (to reflect the digital zoom), while the image in the EVF remains the same size, with a shaded border to indicate the crop. The digital zoom cannot be used with RAW images or in Movie mode.
A set of 49mm filter threads around the inside lip of the lens barrel accommodates Minolta’s range of accessory filters and conversion lens kits. (We really liked having the fixed filter threads on the front element of the zoom lens, making it easy to attach auxiliary lenses and filters without any additional adapters or other gadgets.)
Our resolution tests indicate that the Dimage 5's lens is of particularly high quality, as it produced very sharp images from corner to corner. The vast majority of digicams we've tested tend to get soft in the corners, distorting and blurring details. By contrast, the Dimage 5 and Dimage 7 are amazingly sharp across the entire frame. We also noticed that the lens showed significantly less chromatic aberration than we're accustomed to seeing, most likely due to the larger-than-normal lens elements and multiple ED elements and aspherical surfaces. Overall, this looks like a great piece of optics!
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