Sony A35 Optics
Sony A35 Optics
Sony A35 Kit Lens
The Sony A35 is available in two versions -- body only, and bundled with a Sony 18-55mm f/3.5-5.6 DT SAM kit lens for about US$100 more which is a pretty good deal considering the same lens sells for about $200 separately. The kit lens has a typical optical zoom ratio of approximately 3x which translates to a 35mm equivalent focal length range of about 27-83mm. Optical construction consists of 8 elements in 7 groups, with a 7-blade circular diaphragm for aperture control. Minimum focusing distance is 25cm or 9.8 inches for a maximum magnification ratio of about 0.34x or 1:2.9 at 55mm. The lens accepts filters with 55mm thread and the front element does rotate. Minimum length is 69mm or 2.7 inches, while diameter is 69.5mm or 2.7 inches. Weight is about 210 grams or 7.4 oz. As with many kit lenses these days, the lens body and mount are mostly plastic to reduce cost and weight. The lens features an AF/MF focus switch to switch between autofocus via the built-in "Smooth Autofocus Motor" (SAM) and manual focus via the focusing ring.
We've tested this lens on a 12-megapixel Sony A700 body over at our sister site SLRgear.com, where it performed well for a kit lens. See below for some test results from another sample of the same lens with a 16-megapixel Sony A35.
Sony A35 Lens Compatibility
The Sony A35 features a bayonet lens mount, which accommodates a range of Sony and Konica Minolta AF lenses. A small button on the front of the camera releases the lens from its mount, so it can be turned and removed. The A35's CMOS sensor 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.)
A depth-of-field preview button can be found adjacent to the grip, at the base of the lens mount. When held in, the A35 stops down the lens aperture to the selected value, and adjusts preview sensitivity to attempt to show the image with correct brightness.
Sony A35 Autofocus
The Sony A35 provides both manual and automatic focus control modes, set by the Focus Mode switch on the left side of the camera body, unless the lens itself has a Focus Mode switch. If there's a duplicate switch on the lens, it takes over this function, and the one on the body serves no purpose. With whichever switch is applicable, 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 fifteen-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 three points at the horizontal center of the frame utilize a cross-type sensor, sensitive to detail in both the horizontal and vertical axis. The other 12 sensors are line-type, sensitive to detail in one direction only.) 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 square 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 fifteen AF points. The selected AF area is indicated with an orange frame during selection, and with a black frame in the viewfinder while framing images, while unselected points have a light gray frame.
Sony A35 AF Assist
The Sony A35 uses its built-in flash head as an 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 it's rather distracting, and 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 well below those it can focus at. (Although its low-light focusing ability is better than average.) 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 A35 Anti-Shake
The Sony A35 also employs Sony's SteadyShot INSIDE anti-shake technology, which uses a highly sensitive accelerometer and image sensor shift mechanism to move the sensor assembly itself to counteract camera movement, rather than the more common approach of moving an optical element inside the lens. Sony claims that the SteadyShot anti-shake system in the A35 provides a 2.5 to 4-stop reduction in the blurring produced by camera shake. 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 SteadyShot is activated, the SteadyShot scale on the right side of the viewfinder display indicates the degree of stabilization. What's more, because the A35's LCD and EVF display the image as seen by the imaging sensor, the effect of SteadyShot stabilization at work can be seen, unlike models that use a traditional optical viewfinder. The SteadyShot scale is still useful even with the stabilized view though, as it gives you a good idea of how hard the SteadyShot mechanism is working, so you can choose a moment when the camera is moving less to snap the shutter, thus maximizing your chances for a sharp image.
Sony A35 Anti-Dust Technology
To help combat dust particles on the sensor from changing lenses, Sony included both an anti-static coating on the sensor filter and anti-dust vibrations to automatically shake the sensor with the anti-shake mechanism each time the camera is shut off. There is also a manual cleaning mode, where the camera opens the shutter, allowing access to the sensor for use with a blower or other cleaning device. The "translucent" mirror must be manually raised to access the image sensor, and it's important not to touch the mirror in the process. There's no user method for cleaning the mirror itself, with the only option if this is required being to return the camera to Sony for service.
We've generally found dust-removal systems based on cameras' anti-shake systems less effective than those that use an vibrate the sensor ultrasonically, but it bears noting that no dust removal system completely eliminates the need for occasional manual sensor cleaning. Copper Hill Images is an advertiser of ours, but we'd recommend their wet/dry cleaning system even if they weren't (it's what we use in our own lab): See the Copper Hill website for details.
Sony A35 Optical Test Results
Below are the results of our optical tests with the Sony A35 and the bundled 18-55mm kit lens. The test images shown on most other pages of this review were taken with very sharp references lenses, so we use this page to explore kit lens quality.
Lens Test Results
Typical performance with the 18-55mm kit lens.
|18mm @ f/8||55mm @ f/8|
The Sony SLT-A35 is available bundled with a 18-55mm f/3.5-5.6 SAM lens. This lens possesses a very typical optical zoom ratio of about 3x, with a 35mm equivalent focal range of about 27-83mm because of the A35's 1.5x "crop factor". Performance at wide-angle was pretty good though slightly soft overall at f/8. Some chromatic aberration is however evident along the edges and corners, and some flare is visible around the building's white surfaces. Results at the 55mm setting were also slightly soft, though chromatic aberration and flare are negligible. Overall, decent results for a kit lens. See below for comments on macro performance, geometric distortion, corner softness, etc.
An average sized minimum coverage area, with very good detail. Flash throttled down well.
|Macro with 18-55mm
kit lens (55mm @ f/8)
|Macro with Flash|
As with zoom performance, the Sony A35's macro performance will depend entirely on the lens in use. However with the 18-55mm kit lens set to 55mm, the SLT-A35 captured an average sized minimum area measuring 2.40 x 1.60 inches (61 x 41 millimeters). Detail was quite good in the center, though corners were moderately soft. (Most lenses have some softening in the corners at macro distances.) The flash did a very good job throttling down, resulting is a well exposed image. The flash also had no trouble clearing the lens as there is no detectable shadow, though the bottom of the image is slightly darker than the top.
Higher than average geometric distortion at wide-angle, very low at telephoto.
|Barrel distortion at 18mm is 1.1 percent|
|Pincushion distortion at 55mm is less than 0.1 percent|
The Sony A35's 18-55mm kit lens produced about 1.1 percent barrel distortion at wide-angle, which is higher than average and noticeable in some of its images. At the telephoto end, there's only about one pixel's worth of pincushion distortion, which is is difficult to detect in images. 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).
The Sony A35 does not appear to be applying any geometric distortion correction to its JPEGs, as uncorrected RAW files show the same amount of distortion.
Chromatic Aberration and Corner Sharpness
Moderately high chromatic aberration at wide-angle; lower levels at full telephoto. The lens produced some soft corners, especially at wide-angle.
Chromatic Aberration. Chromatic aberration in the corners with the SLT-A35's 18-55mm kit lens at wide-angle (18mm) is moderate in terms of the number of pixels, but quite bright, so the effect is noticeable in some shots. (The effect is even brighter than shown in the crop above for corners that are sharper.) At full telephoto (55mm), CA is also moderate in terms of pixels, but the colors in the fringes are more muted, partially due to a loss of contrast. Color fringing gradually reduces in brightness and width as it approaches the center of the image, where it is very low at wide-angle and telephoto.
Corner Softness. Wide-open at full wide-angle, the copy of the 18-55mm lens that came with our A35 was quite soft in the right corners, and the softness extended pretty far into the frame. The extreme left corners we also soft, though not quite as soft as the right, and softness didn't extend very far into the frame at all from the left. The center of the image was sharp with very good contrast. Some vignetting (corner shading) is also noticeable at full wide-angle, as indicated by the darker corner crop. At full telephoto, the left side was softest, but not nearly as soft as wide-angle. The corners in the right hand-side were sharper but still as touch soft, as was the center. The lens also had lower contrast overall at full telephoto.
The Sony A35 doesn't appear to be applying any chromatic aberration in its JPEGs, as uncorrected RAW files show similar amounts.
"Stopped-down" to f/8, performance in the corners at wide-angle improved slightly compared to wide-open at f/3.5, but corners were still soft, with the lower-right being the softest. At telephoto, corners were actually a bit softer at f/8 versus wide-open at f/5.6, but the center remained fairly sharp.
Overall, an average performance for a kit lens.
Internal Mirror Reflections
|Sony SLT-A35, 18-55mm kit lens||Sony DSLR-A560, 18-55mm kit lens|
When additional surfaces are added to an optical path, especially ones not parallel with the image plane, there is always a chance that light will travel an unintended path. In the case of the A35 (as well as the A33 and A55 before it), it appears that the rear surface of the "translucent" mirror film can reflect light back to the front surface of the film, which reflects it back to the rear, causing a "ghost" reflection or multiple reflections to appear in the final image under certain conditions. The above left crop shows this phenomenon in one of our Sony A35 flash test shots, where a very strong reflection from the plastic edging of our flash-range/uniformity target also has a small ghost image in the form of a horizontal white line below it. The crop on the right is from a similar flash shot, taken with the same model lens, but using the Sony A560 which is a traditional SLR without a "translucent" mirror in the optical path. As you can see, under nearly identical conditions (the A560's flash is a bit stronger), no ghosting is present.
Should you be concerned about it? Perhaps. Some people would certainly find it objectionable, especially if they did a lot of night photography of things like cityscapes where this ghosting phenomenon is more likely to appear. Personally, it wouldn't deter us from buying a Sony A35, because we don't do much cityscape-type photography: Our night shots tend to be ones where the subjects are people or areas lit by nearby light sources. With these sorts of shots, ghosting of the type shown above wouldn't be an issue. Bottom line, you'll need to decide for yourself if this would impact your personal style of shooting enough to outweigh the benefits of the Sony A35's pellicle mirror design.
Sony A35 Viewfinder
The Sony A35 features a "translucent" (transparent is technically more accurate) mirror design that necessitates use of full-time live view, and so adopts an electronic viewfinder, rather than the true optical viewfinder of a traditional SLR. (While it would perhaps have been possible for Sony to adopt a true optical viewfinder using light reflected by the "translucent" mirror, as was done with certain film SLRs in decades gone by, it would by necessity have been very dim. Hence, the decision to use an EVF is undoubtedly the correct one.)
An important advantage of the Sony A35's electronic viewfinder, as compared to a tradition SLR's optical viewfinder, is that the effect of white balance, exposure settings, and the like can be previewed. This allows the photographer to better understand what to expect from their final image. Also, since an EVF can display essentially anything the main LCD can, it allows you to view the same overlays that you'd see on the LCD, including things like a live histogram that would be simply impossible with an optical viewfinder. The only display mode offered by the A35's LCD that isn't available on the EVF is a full-screen status display that simply wouldn't make sense to use with the viewfinder, since it would prevent any view of the subject itself. If you're suitably familiar with the A35's external controls, the EVF even allows you to browse menus and quickly change settings without taking the viewfinder away from your eye. Optical viewfinders have advantages of their own, though. They use no battery power, providing a significant advantage over framing images on an LCD display -- and this is particularly significant given that the A35's EVF actually uses more power than the main LCD panel does. (Battery life with flash usage, to CIPA standards, is rated as 440 shots when using the LCD, but falls to 420 shots with the EVF.) There's also something to be said for the image viewed through a really nice optical viewfinder, something even the best electronic finders struggle to match with current technology.
We don't currently have details on the precise viewfinder type employed by the Sony SLT-series cameras, but Sony describes it as a 0.46-inch diagonal (0.43-inch effective) Xtra Fine LCD Tru-Finder. Whatever the type, it clearly employs a time-multiplexed method to display red, green, and blue color information at every pixel location, suggesting that it is likely to be a ferroelectric LCD. These differ from traditional LCD displays, which mostly create color information with a cluster of three adjacent red, green, and blue subpixels (commonly called 'dots'), for each pixel location. When compared to standard LCD electronic viewfinders, ferroelectric types bring both advantages and disadvantages. They've proven somewhat divisive in the past, due to their tendency to demonstrate RGB "rainbow" artifacts when you blink or move your eyes, or with fast-moving subjects. On the positive side, though, since each pixel provides full color, ferroelectric LCDs tend to look much smoother and more detailed than their traditional LCD siblings, with less obvious pixel structure. They also tend to have higher refresh rates, and indeed Sony specs the EVF used in the A35, A55, and A33 as offering a 60Hz refresh rate. It's perhaps not surprising to see such a display adopted by Sony, since Konica Minolta -- the company Sony absorbed to create its DSLR division -- was a particular proponent of their use.
We're pleased to report that the EVF in the Sony A35, A55, and A33 provides better dynamic range than most. Resolution is good, with no noticeable gaps between pixels, and the EVF also does a decent job of preserving highlight detail in high-contrast scenes. The slight distraction caused by the "rainbow" effect is relatively easy to ignore in most usage. In spec sheets for the A35, Sony lists its EVF as having 1,440,000 dots, of which 1,152,000 are effective in the viewfinder display. We believe that the company is following precedent here, by simply reporting a dot count as if each pixel constituted three separate color dots, rather than being time-multiplexed. If that's the case, the actual pixel resolution would be 480,000 total pixels, of which 384,000 are effective in the final image.
It's a little unusual to see an effective pixel resolution for an electronic viewfinder, but we believe the reason effective resolution is some 20% lower than the EVF's actual pixel count is that Sony have selected an LCD with approximately a 4:3 aspect ratio, but are only using the central 16:9 aspect ratio swathe of the display. This is likely done both to match the rear-panel LCD display aspect, and also because even with this crop, the EVF already has a generous 1.1x magnification -- much higher than that of most APS-C DSLRs -- and a somewhat tight eyepoint of 19mm from the viewfinder eyepiece (18mm from the eyepiece frame). Were the whole display used, the eyepoint would fall uncomfortably low -- it's already just a little tight for eyeglass wearers. Thankfully, it includes an unusually wide -4 to +4 diopter adjustment range, better mitigating the tight eyepoint for those with eyeglass prescriptions inside this range. The EVF also has a 100% field of view, and provides three step automatic / manual brightness control.
A pair of horizontal infrared sensors, visibly just beneath the viewfinder in the image above, detect your eye as it approaches, and deactivates the main LCD monitor if you have the Finder / LCD Setting option in the Custom menu set to "Auto". Alternatively, you can disable this function and switch between displays manually, using the Finder / LCD button. This might be advisable if you tend to leave the camera switched on and hanging on its neckstrap, given that it can't differentiate between your eye and chest, and will potentially waste battery life by switching to the more power-hungry EVF panel. You can also set the infrared sensors to initiate autofocus whenever your eye is in range of the eyepiece (Eye-Start AF), which makes the A35's autofocus seem even more responsive.
Viewfinder Test Results
Excellent accuracy from the electronic viewfinder and LCD monitor.
The Sony Alpha SLT-A35's electronic viewfinder and LCD monitor both showed slightly above 100% coverage with our Sigma 70mm f/2.8 prime lens. This is excellent performance, though not a surprise given the viewfinder is electronic and is deriving its image from the main imaging sensor.
The images above were taken from our standardized test shots. For a collection of more pictorial photos, see our Sony Alpha SLT-A35 Photo Gallery .
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