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Minolta Dimage 7 Minolta unleashes the first 5-megapixel camera, with a tack-sharp 7x zoom lens, and amazingly sensitive electronic viewfinder! Select a topic Reference: Datasheet Dimage 7 Sample Images --------------------------------- 1. Intro and Highlights 2. Executive Overview 3. Design 4. Viewfinder 5. Optics 6. Exposure & Flash 7. Shutter Lag & Cycle Time Tests 8. Operation & User Interface 9. Camera Modes & Menus 10. Image Storage & Interface 11. Video, Power, Software 12. Test Results & Conclusion --------------------------------- Print-Friendly Review Version Additional Resources and Other Links Reader Comments on Dimage 7 Review --------------------------------- Digital Camera Comparometer (TM) --------------------------------- <-- Digital Cameras (Home) <-- Digital Camera Reviews Index <<Viewfinder :(Previous) | (Next): Exposure & Flash>> Page 5:Optics Review First Posted: 5/23/2001

Optics
The Dimage 7 is equipped with a 7.2-50.8mm, aspherical glass lens, the equivalent of a 28-200mm lens on a 35mm camera. This is a very nice range of focal lengths. The 28mm wide angle setting is particularly welcome, since most digicam lenses don't go that wide. Likewise, 200mm is a good medium telephoto length, about as long as one can comfortably handhold the camera without image stabilization. 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 aspheric 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 in on objects as close as 5 inches (13 cm) 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 closest focus 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 into 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 7 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 7 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. Our first test unit was an early prototype, and its autofocus was known not to be up to final specs, so we bypassed measuring the autofocus speed. However, Minolta predicts that the final production model is going to be a very quick-focusing camera.

UPDATE, 8/23/2001 - Sadly, this is an area where the camera didn't improve significantly relative to the prototype model: The Dimage 7's autofocus speed is actually a bit below average for its category. We also occasionally found a subject that would unexpectedly give the AF system fits. 98% of the time, it delivered excellent focus, even on subjects that we'd normally expect problems on . (Dark, relatively low-contrast objects, for instance.) The other 2% of the time though, it'd have a terribly hard time achieving focus lock on a seemingly innocuous subject that "should" be easy to focus on. (One having strong, high-contrast detail, for instance. Overall, it seemed that it did the best with subjects having texture, rather than simply strongly contrasting detail elements. This is perhaps a consequence of the phase-detect autofocus system. Overall, we'd say the "success rate" of the Dimage 7's AF system was about on a par with those of other cameras we've used, it's just that it seems to fail on a different sort of subject.

The Dimage 7'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 at all times, continuously keeping the frame in focus. You can also determine the area of the image the camera uses to judge the focus, by selecting one of three autofocus options: Wide Focus Area, Spot Focus Point, and Flex Focus Point. The default options is Wide Focus area, indicated by wide set of brackets in the viewfinder image. By pressing and holding down the center of the Five-Way Arrow controller pad, the camera switches between Wide Area and Spot Point autofocusing modes (the latter indicated by a target crosshair in the center of the viewfinder). If you release the controller pad when the Spot AF target is displayed, you can then use the four arrow buttons to move the target around the viewfinder area -- this is what's known as Flex Focus Point AF. Wide Area AF bases its focus on the most prominent subject detail in the center of the frame, delineated by the viewfinder area that falls within the brackets. Spot Focus bases its focus on the very center of the frame, where the target crosshairs reside. Finally, Flex Focus allows you to move the focus point to anywhere within the frame, by manually moving the target crosshairs around the image area with the arrow buttons. (See the screen shot at right, in which we switch from Wide Area to Spot Focus, and then move the Flex Focus Point around the screen.)

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.

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 subject without having to hold down the Shutter button halfway. Pressing the button also locks exposure. You can configure this button 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 7 offers a 2x Digital zoom button, located at the very bottom of the back panel, on the right side. In Auto Focus, pressing this button activates an instant 2x zoom. In Manual Focus, Minolta recommends using the button to magnify the focusing area, to help establish the correct focus, then return to normal setting to expose the image. (Keep in mind that digital zoom simply enlarges the central portion of the CCD image digitally, rather than magnifying it optically and, as a result, image quality is usually degraded in the form of lower resolution and increased noise.)

A set of 49mm filter threads around the inside lip of the lens 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 7'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 7 is 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 AD elements and aspheric surfaces. Overall, this looks like a great piece of optics, and is a significant part of why we liked the Dimage 7 so much. (Note to other manufacturers: A "killer" digicam is only as good as its lens - Could we *please* have more lenses with corner to corner sharpness and low chromatic aberration? Surely the market would support these!)