Konica Minolta DiMAGE A2Konica Minolta updates their top-end electronic SLR with a higher resolution sensor, much-improved electronic viewfinder, a faster 3D autofocusing system, and high-speed USB 2.0 connectivity, among other improvements.<<Viewfinder :(Previous) | (Next): Exposure & Flash>> Page 5:OpticsReview First Posted: 07/13/2004 |
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Equipped
with a 7.2-50.8mm, glass lens with multiple aspherical elements, the DiMAGE
A2'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 Konica Minolta's
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 A2 still uses
the same lens. Images are sharp corner to corner, with very little of the softness
I've come to expect from digicam lenses in the corners of the frame, although
the A2 is on the lower end of the sharpness scale overall, when compared to
the rest of the 8-megapixel field. - Not to the extent that I'd say it constitutes
a serious reason to pass over the camera in favor of one of the others, but
the softness is visible enough that I felt I should mention it. 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. (Konica 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 A2's macro performance is
less than it actually is.) In my tests, the A2 captured a minimum area of just
1.94 x 1.46 inches (49 x 37 millimeters), a very small area indeed. (This is
essentially the identical minimum macro area as for the A1, based on my direct
measurements, even though Konica Minolta actually lists a slightly larger minimum
area in their specifications for the A2.) You can enter Macro mode in either
maximum wide angle or a small range of telephoto lens positions, the greatest
magnification being available with telephoto focal lengths. 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 A2 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. This system does seem to be pretty effective, as the A2 shows among
the fastest shutter lag times I've seen for autofocus-equipped prosumer digicams.
(A range from 0.39-0.45 seconds with autofocus operating.)
The DiMAGE A2'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, potentially saving a good bit of power. The DiMAGE A2
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 Konica 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 implemented very handy 2x and 8x magnification
options to assist with focusing in the A1. In the A2, this feature seems to
have been replaced with a fixed magnification of 3.3x, falling somewhere into
the middle ground. 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. It is a shame
to see this replaced with a more ordinary 3.3x magnification for the A2, which
should just about be useful - but nowhere near as much so as the A1 was. - The
good news though, is that the exceptional resolution of the EVF display does
somewhat reduce the need for greater magnification. 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), can optionally lock 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 A2 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.)
A set of 49mm filter threads around the inside lip of the lens accommodates
Konica 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. (It does
deserve noting though, that the manually-actuated zoom mechanism on the A2 is
much more robust mechanically than are most electronically-actuated mechanisms
on competing cameras, so it should be much more able to support accessory optics.)
"3D" Predictive Focus Control and Subject Tracking
Based on information from Konica Minolta, the DiMAGE A2 features a fairly sophisticated
autofocus system. When it's running in Continuous Autofocus mode, the A2'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 "Predictive Focus
Control" function could help focus accuracy for moving subjects significantly,
particularly when using long telephoto focal lengths.
The A2 also incorporates Konica Minolta's Subject Tracking AF, which we saw
one form of in their earlier 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
Introduced in the A1 and carried over to the A2 is Konica Minolta's very effective
vibration-reduction system. Konica Minolta's anti-shake technology is unusual
in that it actually moves the CCD assembly to counteract camera movement, rather
than the more common 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 3.3x 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 A2 is very intelligent about when to turn
on Anti-Shake though, by default only activating it when the shutter is half-pressed,
or when the 3.3x 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 A2, 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 A2 is so obviously aimed at will understand and fully appreciate the
value of Anti-Shake technology.
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