Sony A700 Optics

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.

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 .