Sony DSLR-A230 Optics

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Sony A230 Optics

The Sony A230 features a bayonet lens mount, which accommodates a range of Sony and Konica Minolta lenses. The Sony A230 comes bundled with a Sony 18-55mm f/3.5-5.6 SAM kit lens. A separate kit comes with both the 18-55mm and a 55-200mm f/4-5.6 telephoto zoom lens. A small button on the front of the camera releases the lens from its mount, so it can be turned and removed. The A230's CCD is smaller than a 35mm frame, so the angle of view at any given focal length will not be the same as on a 35mm camera. To find the approximate 35mm equivalent focal length, multiply the focal length of the lens by 1.5. (Thus, a 50mm lens will provide about the same view as a 75mm lens on a 35mm camera.)

Alpha lens mount. The Sony A230's Alpha lens mount is compatible with the full array of Alpha lenses, both screw-drive and electronic autofocus models.

The Sony A230 provides both manual and automatic focus control modes, set by the Focus Mode switch on the left side of the camera (when viewed from the back). You can select between Auto and Manual focus modes. The Function button provides access to additional AF modes and AF Area options. The Autofocus Mode option under the Function menu offers Single-shot AF, Automatic AF and Continuous AF settings. Single-shot sets focus with each half-press of the Shutter button, while Continuous mode is constantly adjusting the focus, whether the Shutter button is pressed or not. The Automatic setting will lock focus on a still subject or continually adjust focus on a moving subject, for as long as the Shutter button is halfway pressed.

Autofocus Area also has three options available through the Function menu: Wide, Spot, and Local (manual setting). The default option is a nine-point Wide Focus area, indicated by an array of square focus areas inset within four widely-spaced brackets in the viewfinder image. (Note that only the center point utilized a cross-type sensor sensitive to detail in both the horizontal and vertical axis. The other 8 sensors are line-type, sensitive to detail in one direction only, although the four line sensors at the corners of the AF array are angled, so they'll respond to both horizontal and vertical detail.)

You can override the chosen AF mode by pressing the Spot AF / OK button in the center of the Multi-controller, which defaults to the more accurate center AF point (the latter indicated by a target box in the center of the viewfinder). Wide AF bases its focus on the most prominent subject detail in the portion of the image that falls within the AF brackets. Spot mode bases its focus on the very center of the frame, where the center target resides. The Local setting is Sony's terminology for a manual AF area selection, and lets you manually set the main AF point by using the Multi-controller to highlight one of the nine AF points. The active AF area is briefly illuminated in the viewfinder during focusing.

Sony didn't include a depth-of-field preview button on the A230, nor on any of the new consumer models announced early 2009. Admittedly, that feature is less useful with such a small viewfinder, but this factor might put off some macro and landscape photographers.

Sony A230 AF Assist

The Sony A230 uses its built-in flash head as a very bright AF-assist light for better focusing in dim lighting. This has the advantage that the light from the flash is very bright, but the downside is that you can only get AF assist when the flash head is raised. This is a real limitation for available-light photography, as the camera can expose at light levels below those it can focus at. If the camera is fixed on a tripod, you can work around this limitation, but it's somewhat awkward: With the flash head up, half-press the shutter button to make the camera focus. Then switch the focus mode to manual focus, being careful not to touch the focus ring on the lens. Stow the flash head, and then take your picture. (But don't forget to switch back to AF mode for the rest of your shooting!)

Sony A230 Anti-Shake

The Sony A230 also employs Sony's Super SteadyShot anti-shake technology, which uses a highly sensitive angular rotation sensor and Smooth Impact Drive Mechanism (SIDM) to move the CCD assembly itself to counteract camera movement, rather than the more common approach of moving an optical element inside the lens.

Sony claims that the Super SteadyShot anti-shake system in the A230 provides a 2.5 to 3.5-stop reduction in the blurring produced by camera shake. Translating that into real-world shutter speeds, a two-stop improvement means that a shutter speed of 1/30 second would give you the same resistance to blur from camera shake that a speed of 1/120 would without anti-shake. A 3.5-stop improvement would mean you could shoot as slow as 1/11 second and get the same results (blur-wise) as when shooting at 1/120 second unaided. Even the lower end of the specified range of effectiveness means a pretty significant improvement in one's ability to hand-hold long exposures.

When Super SteadyShot is activated, the SteadyShot scale on the right side of the viewfinder display indicates the degree of stabilization. A downside to Sony's body-based SteadyShot approach is that while you can see the results of stabilization on competing lens-based designs, you have only this scale to tell you how the A230's SteadyShot mechanism is doing. SteadyShot minimizes the effect of blurring caused by slight camera movement, which is more noticeable at long focal lengths.

Sony A230 Anti-Dust Technology

To help combat dust particles on the CCD from changing lenses, Sony included both an anti-static coating on the CCD filter and anti-dust vibrations to automatically shake the CCD with the anti-shake mechanism each time the camera is shut off. There is also a manual cleaning mode, where the camera lifts the mirror and opens the shutter, allowing access to the sensor for use with a blower or other cleaning device.

Sony A230 Optical Test Results

Below are the results of our optical tests on the Sony A230. We used the 18-55mm kit lens as the benchmark, since most people will buy and use the camera in this configuration.

Kit Lens

Zoom
Good performance with the 18-55mm kit lens, but some variability from sample to sample.


18mm	55mm

The Sony Alpha 230 comes with an 18-55mm kit lens, which has a typical optical zoom range of ~3x. Details are a bit soft in the center of the frame at full wide-angle, with low levels of coma distortion but some minor blurring and chromatic aberration in the corners. Results at full telephoto are better with very little corner softness or chromatic aberration, but still a hint of softness across the frame. Lacking a Live View option, the Sony A230 doesn't have the "Smart Teleconverter" digital zoom mode that the A330 and A380 have.

The particular sample of the 18-55mm kit lens used for the shots above was pretty good, so we used that lens for all our kit-lens shots with the Spring 2009 A-series models. We did find some variation between the lenses we received with the three cameras, though: It's always a good idea to check that newly-bought lenses are focusing well and evenly across the frame, but the variation we saw among the Sony 18-55mm samples we had in our lab is good reason to remind our readers of this. The A230 also seemed to back-focus somewhat with the kit lens, but it's less evident in these shots, taken at ~infinity, and with the lens stopped down to f/8.

Macro
A slightly large macro area with the kit lens, with good detail but soft corners. Flash throttles down pretty well.


Macro with 18-55mm Kit Lens	Macro with Flash

The Sony A230 captured a slightly larger macro area than average with the standard 18-55mm kit lens, measuring 2.35 x 1.57 inches (60 x 40 millimeters). Detail was fairly strong near the center of the frame, though corners were quite soft. (Most lenses have some softening in the corners at macro distances.) The A230's flash throttled down for the macro area pretty well, despite the slight overexposure.

Geometric Distortion
High barrel distortion at wide-angle with the 18-55mm kit lens, though hardly any distortion at telephoto.

Barrel distortion at 18mm is 1.0 percent

Almost no distortion at 55mm

The Sony A230's 18-55mm kit lens produced about 1.0 percent barrel distortion at wide-angle, which is higher than average and noticeable in its images. At the telephoto end, there was only about 1 pixel of barrel distortion which is essentially nonexistent. This is the tendency for the lens to bend straight lines outward (like a barrel -- usually at wide-angle) or inward (like a pincushion -- usually at telephoto).

Chromatic Aberration
Moderate at wide-angle, but low at telephoto with the 18-55mm kit lens.


Wide: Moderate, top left	Wide: Moderate, top right

Tele: Low and dull, top left	Tele: Low and dull, top right

Chromatic aberration was moderate at the full wide-angle setting of the Sony A230's 18-55mm kit lens, showing about 4-6 pixels of bright coloration on either side of the target lines. At telephoto, chromatic aberration is much lower and hardly noticeable. (This distortion is visible as a slight colored fringe around the objects at the edges of the field of view on the resolution target.)

Corner Sharpness
Minimal blurring in the corners of the frame at wide-angle and telephoto with the kit lens, but soft at center (back-focus issue).


Wide: Slightly softer in the corners (upper right).	Wide: Soft at center.

Tele: About the same sharpness in the corners (upper right).	Tele: Soft at center.

Our sample of the Sony A230 seemed to generally be back-focusing (focusing a bit behind the target) with the kit lens in this test. The center is rather soft at both wide angle and telephoto (worse at wide angle), but the corners are relatively sharp, at least for a kit lens. After some analysis, it appears that the A230 was focusing a bit behind the target here: When combined with the curvature of field of the kit lens, this meant that the corners were in better focus than the center. For comparison, see the examples below, shot with the same lens on the Sony A330.


A330, Wide: Low to moderate softness in the corners (upper right).	A330, Wide: Fairly sharp at center.

A330, Tele: Slightly soft in the corners (upper right).	A330, Tele: Slightly soft at center.

The shots above show more typical behavior with the kit lens, shot on the A330. Here, the center of the target is sharper (especially in the wide angle example), but the corners are softer. We often see minor front- or back-focusing on cameras we test, but our sample of the A230 was worse than average in this regard. It appeared that its focus errors were limited to the kit lens, though, as shots taken with the Sigma 70mm f/2.8 macro lens we use for of the test shots were well-focused. Ditto the Far-Field shots, which were taken with the Sony 24-70mm f/2.8 Carl Zeiss optic. We found a good bit of variability in focusing between the A230/330/380 and the various kit lenses we received with them, so have developed an unfavorable opinion of that lens. The A230 body did appear to be back-focusing with most of the kit lens samples, though. Front/back focus can generally be corrected by having the camera serviced, but if it's a newly-purchased unit, we'd suggest asking the retailer for an exchange.

The images above were taken from our standardized test shots. For a collection of more pictorial photos, see our Sony Alpha DSLR-A230 Photo Gallery .