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Minolta DiMAGE A1 Minolta updates their revolutionary five-megapixel electronic SLR with faster shutter speeds, an Anti-Shake mode, 14-bit A/D, and a tilting LCD monitor, among other improvements. Select a topic Reference: Datasheet A1 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 A1 Review --------------------------------- Digital Camera Comparometer (TM) --------------------------------- <-- Digital Cameras (Home) <-- Digital Camera Reviews Index <<Viewfinder :(Previous) | (Next): Exposure & Flash>> Page 5:Optics Review First Posted: 08/08/2003, Updated: 11/10/03

Optics

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Equipped with a 7.2-50.8mm, glass lens with multiple aspherical elements, the Dimage A1's lens is equivalent to 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 without accessory lens adapters. Likewise, 200mm is a good medium telephoto length, about as long as most folks can comfortably hand-hold without image stabilization, although Minolta's new Anti-Shake feature should greatly help out here. Unlike most digicams I've worked with, the lens zoom operates by rotating a collar around the lens barrel, coupled mechanically to the lens elements themselves. I like the 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. (I will say that the action of the zoom lens feels a little "cheap" though, with more of a plastic-on-plastic feel, rather than the smooth lubricated-metal feeling I'm accustomed to in higher-end removable SLR lenses.)

The lens consists of 16 elements in 13 groups, including two AD (anomalous dispersion) glass elements and two aspheric surfaces. All that dispersion/aspheric mumbo-jumbo is by way of explaining that this is a very high quality lens. Way back when I first tested the original DiMAGE 7, I was amazed by how little distortion and corner softness it displayed, and as far as I can tell, the A1 still uses the same lens. Images are very sharp corner to corner, with very little of the softness I've come to expect from digicam lenses in the corners of the frame. Aperture control can be either manual or automatic, with a maximum aperture 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 focuses in on objects as close as about 5.25 inches (13.3 centimeters) from the lens surface in telephoto mode. (Minolta follows the practice from film-based photography of specifying focusing distance from the "film" (CCD) plane of the camera, rather than the front element of the lens. This avoids confusion over distances as the length of the lens changes in response to zoom adjustments, but would lead one to expect that the A1's macro performance is less than it actually is.) In my tests, the A1 captured a minimum area of just 1.96 x 1.47 inches (50 x 37 millimeters), a very small area indeed. You can enter Macro mode in either maximum wide angle or a small range of telephoto lens positions. 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 has an eyelet for attaching a strap, to prevent it from being accidentally lost.

The DiMAGE A1 provides both manual and automatic focus control. The camera's specification sheet describes the autofocus system as a "Video AF system," which uses phase-detection focusing technology rather than the much more common contrast-detection system. The advantage 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 should be able to 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. The D7Hi was one of the fastest-focusing prosumer digicams I'd tested, and my testing of a production model A1 showed that it was at least as fast.

This system does seem to be pretty effective, as the A1 shows some of the shutter lag times are among the fastest I've seen for autofocus-equipped prosumer digicams.

The DiMAGE A1'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. While this definitely demands more power from the battery, the grip sensors on the front of the hand grip tell the camera to focus only when being held. The DiMAGE A1 lets you determine the area of the image the camera uses to set the focus from, by selecting one of three autofocus options: Wide Focus Area, Spot Focus Point, and Flex Focus Point. The default option is Wide Focus area, indicated by a set of four widely-spaced brackets in the viewfinder image. By pressing and holding down the center of the Four-Way Arrow controller pad, you can switch 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 Minolta calls Flex Focus Point AF. Wide Area AF bases its focus on the most prominent subject detail in the portion of the image that falls within the AF brackets. Spot Focus bases its focus on the very center of the frame, where the target crosshairs reside. Finally, Flex Focus lets you move the focus point to anywhere within the frame, by manually moving the target crosshairs around the image area with the arrow buttons.

The Focus switch on the camera's left side toggles back and forth between Single AF, Continuous AF, and Manual focus modes. In Manual Focus mode, turning the ribbed ring around the base of the lens barrel adjusts focus. As you focus, a distance readout reports the current focal distance in meters or feet at the bottom of the LCD monitor (or EVF), under the MF icon. The Direct MF menu option lets you manually tweak the autofocus selection without explicitly switching over to MF mode. You simply halfway press the Shutter button (triggering the autofocus system) and then rotate the focus ring to fine-tune the focus. This is useful when the camera is having trouble focusing on a difficult subject, but isn't too far off the mark.

As mentioned earlier, Minolta has implemented very handy 2x and 8x magnification options to assist with focusing. In my experience, 2x really isn't enough to determine fine focus using a camera's LCD screen, and 4x is a help, but only marginally adequate. The 8x option offered by the A1 was a revelation though, letting me set focus very precisely, shot after shot, on a wide variety of subjects. Even relatively small movements of the focusing ring produced very noticeable changes in the magnified display. The manual-focus focus-assist magnification disappears as soon as you half-press the Shutter button, or press the magnify button a second time.

The AE Lock button, located in the upper right corner of the back panel (below the Mode dial), locks the focus for a specific portion of the subject without having to hold the Shutter button down halfway. Pressing this button can also lock exposure. You can configure this button in the settings menu to switch between AF/AE Hold, AF/AE Toggle, AE Hold, or AE Toggle functions.

In addition to the 7x optical zoom, the DiMAGE A1 offers 2x Digital zoom. By default, pressing the Magnification button on the top panel activates an instant 2x digital zoom. (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 resolution decreases in direct proportion to the magnification achieved.) In Manual Focus, this button optionally produces the temporary magnification of 2x or 8x mentioned above.

A set of 49mm filter threads around the inside lip of the lens accommodates Minolta's range of accessory filters and conversion lens kits. I really like 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. I do worry a little about the wisdom of hanging very much weight on the front of the telescoping lens assembly though. I guess it will be fine for relatively lightweight attachments such as macro adapters and filters, but I advise caution with any sort of larger accessory lens.

"3D" Predictive Focus Control and Subject Tracking
Based on information from Minolta, the A1 appears to have a much more sophisticated AF system than found on previous Minolta digicams. Details are a little sketchy, but when it's running in Continuous Autofocus mode, the A1's AF system monitors the focusing distance, and projects it into the future. Using this information, it continues to adjust the focus during what would otherwise be the "dead" time between when the shutter button is fully pressed and when the camera actually snaps the picture. This could help focus accuracy for moving subjects significantly, particularly when using long telephoto focal lengths.

The A1 also incorporates Minolta's Subject Tracking AF, which we saw one form of in their F100 and F300 consumer cameras. If you put the camera in Continuous Autofocus mode and half-press and hold down the shutter button, the camera will lock on and track a moving subject across the frame, adjusting focus as appropriate. You need to initially have the subject under the active AF point, but from that point on, it will follow the subject around the frame. I really don't have an ability to evaluate capabilities like this quantitatively, but in playing with it a bit, the AF point did indeed track subjects fairly well, across perhaps 80% of the total frame area. I couldn't move the camera too rapidly, or it would lose the subject, sometimes hopping and re-locking on an adjacent object, but the capability still goes quite a bit beyond what's available in other cameras on the market.

Anti-Shake System
rand new in the A1 is the first vibration-reduction system on a Minolta digicam. Details on it are sketchy, but it apparently actually moves the CCD assembly to counteract camera movement, rather than the more usual approach of moving an optical element inside the lens. I didn't conduct any sort of a formal test with it, not having any quantitative way to measure its effects. I did find it very effective (surprisingly so). To see the effect "live," I ran the zoom all the way out to full telephoto, then turned on the 8x focus-assist magnification on the LCD. With Anti-Shake inactive, it was virtually impossible to keep the resulting LCD image stable when holding the camera by hand. When I turned Anti-Shake on, the results were immediate and dramatic. The image quieted down by what had to be a factor of four or more.

In my power testing, I found that Anti-Shake exacts a stiff price in terms of power consumption, increasing power drain by fully 70% over similar operating modes with Anti-Shake disabled. The A1 is very intelligent about when to turn on Anti-Shake though, by default only turning it on when the shutter is half-pressed, or when the 2x or 8x viewfinder magnification mode is enabled. A menu option lets you further restrict Anti-Shake operation to the actual moment of exposure itself, reducing the power hit even more.

I don't know how much of a premium the Anti-Shake function adds to the cost of the A1, but hope it isn't too much. Optical stabilization makes a huge difference in usability of longer telephoto focal lengths, but is a feature that has found little support from a price standpoint in the past. (Other cameras incorporating optical stabilization have generally not fared well against cheaper competition lacking the feature.) I'm hopeful though, that the range of sophisticated user that the A1 is so obviously aimed at will understand and fully appreciate the value of Anti-Shake technology.