Sony A700 Optics

The Sony A700 features a bayonet lens mount (Minolta A-type), which accommodates a range of Sony and Konica Minolta lenses. The A700 ships in two bundles, one with the Sony 18-70mm f/3.5 lens found in the original A100 kits, and the other with a new 16-105mm f/3.5-5.6 kit lens. A small button on the front of the camera releases the lens from its mount, so it can be turned and removed. The A700'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 100mm lens will provide about the same view as a 150mm lens on a 35mm camera.)

The Sony A700 provides both manual and automatic focus control modes, set by the Focus Mode switch on the left side of the camera. You can select between Single, Auto, Continuous and Manual focus modes. Single AF autofocuses once when you initially press the shutter button halfway. Continuous AF mode will continue adjusting focus as long as you hold the shutter button half-pressed. Auto AF mode will focus once if the subject is stationary, but continuously if it detects subject motion.

Manual focus mode has a couple of handy options. If you half-press and hold down the shutter button in Manual focus mode, the viewfinder focus indicator will tell you when the camera thinks the image is in focus. Better yet, if you press the AF/MF button on the back of the body (conveniently located right under your right thumb), the camera will momentarily take control and set the focus, returning control to the focus ring on the lens when you release the button.

There are three options for Auto Focus Area, set via the "Quick Navi" screen on the rear-panel LCD (accessed via the Fn button): Wide Focus Area, Spot AF Area, and Local or Focus Area Selection. The default option is an 11-point Wide Focus area, indicated by an array of dashes arrayed across the central area of the viewfinder frame. You can override the chosen AF mode by depressing the Multi-Selector joystick, which switches to the more accurate center AF point (the latter indicated by a target box in the center of the viewfinder). 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 square target resides. The Local or Focus Area Selection option lets you manually set the main AF point by using the Multi-Selector to highlight one of the 11 AF points. The active AF area is briefly illuminated in the viewfinder. Unlike its progenitor, the Konica Minolta 7D, there's no "lock" setting for focus area selection on the Sony A700: The Multi-Selector joystick is always live.

Sony A700 AF Assist

Unlike the Sony A100, which used its flash for AF-assist lighting, the Sony A700 has a very bright LED built into the body, that projects a pattern onto the subject for better focusing in dim light. The disadvantage of an LED is that it isn't as bright as the flash, limiting the distance at which the AF illuminator can work. The LED has several advantages though, including that you don't need to use the flash to have AF assist work, a huge benefit for available-light photography.

The pattern projected by the LED is also a significant help when dealing with low-contrast subjects. Thanks to the projected pattern, the Sony A700 can focus on a blank wall in total darkness. (Not that a blank wall would make a particularly interesting subject, but if it can handle that, it can probably handle most any normal subject.)

Sony A700 Anti-Shake

The A700 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. This body-based anti-shake approach is based on technology Sony acquired from Konica Minolta, but Sony claims that their more powerful processors increase the system's effectiveness beyond that of similar systems in the original Konica Minolta SLR models. (Theoretically, a faster CPU could let the system respond to and compensate for higher-frequency vibrations, and/or use a more sophisticated algorithm for matching the vibration pattern of the camera.)

Sony claims that the Super SteadyShot anti-shake system in the A700 provides a 2.5 to 4 stop reduction in the blurring produced by camera shake, a half-stop better than was claimed for the A100. Translating that into real-world shutter speeds, a 2.5-stop improvement means that a shutter speed of 1/25 second would give you the same resistance to blur from camera shake that a speed of 1/125 would without anti-shake. A 4-stop improvement would mean you could shoot as slow as 1/8 second and get the same results (blur-wise) as when shooting at 1/125 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 A700's SteadyShot mechanism is doing. SteadyShot minimizes the effect of blurring caused by slight camera movement, which is more noticeable at long focal lengths.

We're working on a protocol for quantitative measurement of anti-shake performance, but haven't tested the Sony A700 with it yet. That said though, the system on the Sony A700 seemed to be pretty effective. In the past, we've generally found that body-based anti-shake systems were more effective at compensating for lower-frequency, larger-amplitude camera shake than were lens-based systems, but less effective with higher-frequency vibration. Body-based systems have also generally seemed to be more effective with shorter focal length lenses than long telephotos, perhaps because body-based sensors may be less sensitive to angular movement than lens-based sensors are to the corresponding linear motion out along the lens barrel where the motion sensor is presumably located. Finally, lens-based anti-shake systems do have a practical advantage in that they also stabilize the view in the optical viewfinder, while sensor-based ones do not. We'll report more on our experience with the A700's anti-shake and make some quantitative comparisons with the performance of some other systems at some point, hopefully in the near future. There's no question, though, that even with telephoto lenses, the A700's Super SteadyShot anti-shake system produces a dramatic improvement in the sharpness of handheld photos at slow shutter speeds.

Anti-Dust Too?

In an interesting wrinkle, Sony also appears to be using the same actuators used in the anti-shake system to deliberately vibrate the sensor at startup and shut down to dislodge dust particles that may have landed on its surface. This is reminiscent of the hypersonic dust-removal system pioneered by Olympus and also recently adopted by Canon and Nikon, but it appears that the vibrational frequencies used in the Sony system are much lower than the ultrasonics used by Olympus and Nikon, and to a lesser extent, by Canon.

In our experience, no anti-dust system will entirely eliminate the need to clean your sensor, so we strongly suggest that you avail yourself of a good sensor-cleaning system of your own. We don't pretend to have used everything currently on the market, but can tell you about one solution that worked very well for us. The "Copper Hill" cleaning method is straightforward and safe, and in our routine usage here at Imaging Resource, highly effective. Better yet, the products sold by Copper Hill Imaging are very reasonably priced. Best of all, Nicholas R (proprietor of Copper Hill) has put together an amazingly detailed tutorial on sensor cleaning, free for all.


Sony A700 Optical Test Results

Below are the results of our optical tests on the Sony A700. These tests are based on the 18-70mm f/3.5-5.6 and 16-105mm f/3.5-5.6 kit lenses, as these are the lenses most people will be buying the camera with. Some results shown here for the 18-70mm are from the earlier A100. Results should be similar on the A700, apart from the fact that optical artifacts (chromatic aberration, softening, etc) will be more apparent on the A700 due to its slightly higher resolution/smaller pixels.


Good performance from the 16-105mm and 18-70mm kit lenses.

Results from 16-105mm kit lens

The Sony A700 is offered body-only, or bundled with either the Sony SAL-1870 18-70mm f/3.5-5.6 lens, or the new SAL-16105 16-105mm f/3.5-5.6 lens. Here, we can clearly see the advantage in focal length range the 16-105mm has over the 18-70mm below.

The 16-105mm is fairly sharp across the frame, but does show a little softening in extreme corners at wide angle. It also exhibits a bit more chromatic aberration than the 18-70mm at wide-angle, which is understandable given the increased range. Results at telephoto are also quite good, but the increase in chromatic aberration over the 18-70mm telephoto shot is more dramatic. While the 18-70mm has virtually no CA at full telephoto, the 16-105mm shows 6-7 pixels of bright coloration around high contrast objects near the edges of the frame. The 16-105mm's increased pincushion distortion at full telephoto is also quite evident.

Results from 18-70mm kit lens

Detail with the 18-70mm is good at full wide angle, with good definition throughout the frame, though with slightly soft corners. There's also a small amount of coma distortion in the top corners. Results are also very good at full telephoto, though again, with slight softening in the corners of the frame.

The 16-105mm produces an average size macro area for a kit lens, though good detail and resolution. Flash performs well also. The 18-70mm gets a bit closer.

Results from 16-105mm kit lens
Macro Macro with Flash

The Sony SAL-16105's macro performance was average for a kit lens, capturing a minimum area of 3.92 x 2.61 inches (100 x 66 millimeters). Detail and resolution were both good, though there's a moderate amount of softening in the corners, as well as some vignetting in the extreme corners. (Most lenses have some softening in the corners when focusing at macro distances, the vignetting is less common.) Performance will naturally be better with a true macro lens, but the kit lens does a decent job in the macro area. The A700's flash did a good job of throttling down, and provided even coverage.

Results from 18-70mm kit lens (shot on A100)
Macro Macro with Flash

From our testing with the Sony A100, we can see it gets a little closer for macro shots, capturing a minimum area of 3.12 x 2.09 inches (79 x 53mm). It also exhibited less vignetting in the extreme corners than the 16-105mm.

16-105mm: Higher than average barrel and pincushion distortion.
17-80mm: Higher than average barrel, almost no pincushion distortion.

Results from 16-105mm kit lens
Barrel distortion at 16mm is 0.9%
Pincushion at 105mm is 0.3%

The 16-105mm SAL-16105's 0.9% barrel distortion at wide angle is just a little more than average among the cameras we've tested, and quite noticeable in some of its images. At the telephoto end, the SAL-16105's pincushion distortion is 0.3%, also higher than most, and again noticeable in some images. (It bears noting though, that long-ratio zoom lenses very commonly show greater distortion than shorter-ratio designs. At roughly 6.6x, the SAL-16105 is a longer-ratio zoom than most kit lenses, and so should perhaps be judged accordingly.)

Results from 18-70mm kit lens (shot on A100)
Barrel distortion at 18mm is 0.9%
Pincushion at 70mm is 0.03%

The 18-70mm lens shows almost identical distortion at the wide angle end, but at its longest telephoto setting, shows almost no pincushion distortion.

Distortion 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
16-105mm: Moderately high, with noticeable effect on some images at edges, extends a ways into the frame.
18-70mm: Moderately high at 18mm, extends a ways into the frame. Very little aberration at 70mm.

Results from 16-105mm kit lens
Wide: Moderately high and bright,
top left @ 200%
Wide: Moderately high and bright,
top right @ 200%
Tele: Moderately high and bright,
top left @200%
Tele: Moderately high and bright,
top right @200%

Chromatic aberration in the 16-105mm kit lens is moderately high at wide angle, showing about 6-7 pixels of bright coloration on either side of the target lines. (This distortion is visible as a very slight colored fringe around the objects at the edges of the field of view on the resolution target.) At telephoto, chromatic aberration is also moderately high. The effect is noticeable in the corners of some of our test shots. As is usually the case, the amount of CA decreases as you move towards the center of the frame, but it's noticeable a fair ways into the frame. (As is the case with distortion, long-ratio zoom lenses very commonly show greater chromatic aberration than short-ratio zoom designs. At roughly 6.6x, the SAL-16105 is a longer-ratio zoom than most kit lenses, and so should perhaps be judged accordingly.)

Results from 18-70mm kit lens (shot on A100)
Wide: moderate, top left @ 200% Wide: fairly bright, top right @ 200%
Tele: quite low, top left @200% Tele: quite low, top right @200%

NOTE: The 18-70mm results above were shot on the Sony A100 camera. Results on the A700 will be similar, but slightly more pronounced, due to the A700's higher resolution. CA on the 18-70mm lens was similar to that of the 16-105mm at its wide-angle end, but very good at its tele end.

Corner Sharpness
16-105mm: Some blurring in the corners of the frame at wide angle and telephoto, doesn't extend too far into the image.
18-70mm: Slight softening in the corners of the frame with the kit lens, though not too strong. More noticeable at telephoto. (Much better than average performance.)

Results from 16-105mm kit lens
Wide: Soft in the corners
(upper left).
Wide: Sharp at center.
Tele: Soft in the corners
(upper left).
Tele: Slightly soft at center.

The Sony SAL-16105 produced soft corners at full wide angle and full telephoto, when wide open (above shots taken at f/3.5 and f/5.6 respectively). The center is quite sharp at wide angle, but a bit soft at full telephoto. The effect is noticeable in some images, however sharpness improves when the aperture is stopped down a few stops, and even wide open, the softness extends only about 15% of the way into the frame from each corner.

Results from 18-70mm kit lens (shot on A100)
Wide Angle:
Slightly soft in the lower left corner.
Wide Angle:
Sharp at center.
Stronger blurring in lower left corner.
Sharper at center, though still a hair soft.

NOTE: The 18-70mm results above were shot on the Sony A100 camera. Results on the A700 will be similar, but slightly more pronounced, due to the A700's higher resolution/smaller pixels. The 18-70mm kit lens produced slightly soft corners in a few shots, with the strongest effect at full telephoto. While the telephoto example above from the lower left-hand corner of our test unit looked pretty soft, that was by far the worst corner, and even there the effect didn't extend too far into the frame. Other corners were much better, overall lens performance was quite good in this area.


The images above were taken from our standardized test shots. For a collection of more pictorial photos, see our Sony Alpha DSLR-A700 Photo Gallery .

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