Sony Alpha SLT-A55 Overview

16.20 Megapixels	Sony Alpha (Minolta A) mount	3.0 inch LCD

Pay Less! $848.26

That's the average, click to find the BEST price!

Sony Alpha SLT-A55 Overview

Reviewed by Dave Etchells, Mike Tomkins, Shawn Barnett and Zig Weidelich
Review Posted: 08/24/2010

Just three months after launching the NEX-3 and NEX-5 single-lens direct-view (SLD) cameras, Sony takes its interchangeable lens offerings in yet another direction with the Alpha SLT-A55, and SLT-A33. Instead of being mirrorless, the new digital cameras employ a "translucent mirror," more commonly known as a pellicle mirror. This advanced translucent mirror remains fixed in place during operation, allowing most of the light to reach the imaging sensor, while a small percentage is reflected to a dedicated autofocus sensor.

It's what this high technology allows that's so exciting: real-time, phase-detect autofocus while firing off up to ten 16-megapixel images per second in the A55, and seven 14-megapixel frames per second in the A33. To get 10 frames per second from any other camera, you'd need to look at professional cameras that cost around $5,000; and they're still not capable of real-time autofocus between shots like the new Sony Alpha SLT cameras. Real-time phase-detect autofocus is also constantly available in Movie mode, something no current SLR can achieve.

While the translucent mirror design isn't quite as space-efficient as the mirrorless design of an SLD camera, it's still smaller than that of a traditional SLR, most of which need to provide room for the mirror to swing upward before image capture can commence. That translates to an uncommonly compact body by SLR standards, although it's still a bit larger than an SLD, especially in terms of body thickness. Unlike SLD cameras, though, the Sony SLT cameras all accept the entire line of standard Alpha-mount lenses, a significant advantage if you already own a large collection of Alpha-mount glass.

Since the translucent mirror only reflects enough light to provide for the autofocus sensor, not an optical viewfinder as most pellicle designs permit, Sony has adopted full-time live view in the Alpha A55 and A33. In place of the optical viewfinder from a traditional SLR, the SLT cameras have an electronic viewfinder with 1,152,000 dot resolution. The EVF LCD is time-multiplexed -- that is to say, it shows each color in sequence at every pixel location, rather than the separate, adjacent color dots of most electronic viewfinders. This makes it harder to distinguish individual pixels. The Sony SLT-series cameras also sport a wide-aspect 3-inch LCD with 921,600-dot resolution. Taking full advantage of the camera's full-time live view shooting, the super-slim LCD tilts 180 degrees vertically, and swivels 270 degrees for easy viewing from most any angle. The cameras also include TruBlack technology borrowed from Sony's picture frames.

Several hot features were brought over from Sony's NEX and Cyber-shot digital cameras, including Sweep Panorama, 3D Sweep Panorama, Auto High-Dynamic Range, and Handheld Twilight modes, each of which strategically combine and align several images into one seamless shot. It's pretty impressive stuff. As if that weren't enough, Sony has added an extra mode for the SLT-series cameras -- Multi-Frame NR -- which operates similarly to the handheld twilight mode, but allows the ISO sensitivity to be specified.

The Sony Alpha A55V, the version sold in the United States, has one standout feature not present in the A55 and A33: a built-in GPS receiver. This allows both still images and movies to be automatically tagged with information about the location at which they were recorded.

The Sony Alpha A55 and A33 will accept both Memory Stick Pro Duo / Pro-HG Duo, and SD / SDHC / SDXC media, and are powered by InfoLithium battery packs.

The Sony A55V and A33 will ship in the US market from mid-October 2010, with pricing of US$850 and US$750 with the body and 18-55mm lens, and $750 and $650 for the body only package.

Sony Alpha A55V User Report

by Dave Etchells, Mike Tomkins, and Shawn Barnett

Rather than rest after establishing product in every major sector of the interchangeable lens digital camera market -- APS-C SLR, full-frame SLR, and most recently single-lens direct view -- Sony is boldly striking out to create yet another category with the launch of its very first translucent mirror cameras. The main goal of the new design: achieving unprecedented autofocus and capture speed from an APS-C sensor, interchangeable-lens, consumer digital camera. Comprising a new SLT series, the Sony Alpha SLT-A55V, A55, and A33 are closely related cameras sharing the same basic design, with only a few internal features as major differences.

Look and feel. Although they lack the reflex mirror of an SLR, having replaced it with a fixed translucent mirror, the basic shape of the Sony SLT-series cameras still follows that of a traditional SLR fairly closely. That's because, since they accept the same Alpha lenses as Sony's DSLRs, the SLT cameras also have to accommodate the same backfocus distance, which is one of the main contributors to the size -- and especially, the depth -- of an SLR camera. Removing the reflex mirror still provides potential for space and weight savings, and Sony has taken good advantage of this. Most obviously, the drive mechanism that raises and lowers the reflex mirror in a traditional SLR isn't needed. The translucent mirror design also provides other opportunities to optimize component placement. As one example of this, Sony has increased the angle of the translucent mirror, so that instead of directing light directly upward at a 90 degree angle as it would for a viewfinder prism, it is actually angled upward and slightly forward, allowing the autofocus sensor to be moved forward, providing more room for the electronic viewfinder assembly directly to the rear.

Comparison. Losing the pentaprism and mirror drive motors helps the A55 achieve a smaller body size than SLRs.

The net result is that, while the Sony Alpha A55 and A33 are a fair bit thicker front-to-back than single-lens direct-view (SLD) cameras, which can do away with the bulky mirror box entirely, they're still exceptionally small cameras by SLR standards. If the handgrip depth is ignored, the SLT-series cameras are actually just a little smaller than the smallest digital SLR to date, the Olympus E-420. Unlike the smallest SLD cameras, the A55 and A33 still include a built-in electronic viewfinder -- and for those SLDs that can accept an optional electronic viewfinder, much of their size advantage over the SLT series is erased once it's installed. Sony's SLT cameras thus occupy a comfortable middle ground, sacrificing little of the versatility of a traditional SLR, yet bringing a worthwhile advantage in portability.

While not quite as light as the Olympus E-420, which lacks an in-body image stabilization mechanism, the Sony Alpha SLT-series cameras are certainly in the same ballpark. Thanks to its added GPS module, the Sony A55V is the heaviest of the trio, weighing 17.6 ounces (1.10 pounds, 500g), with battery and flash card (but no lens), while the Sony A55 and A33 are just a smidgen lighter, at 17.3 ounces (1.08 pounds, 492g). By comparison, the Olympus E-420 weighs 15.7 ounces (0.98 pounds, 445g) loaded but without a lens. The lightest SLD, Sony's NEX-5, weighs just 17.7 ounces (1.1 pounds, 502g) loaded and with its kit lens attached -- just 0.1 ounce more than the A55 body without a lens.

Thanks to their smaller body, and especially their reduced height due to the lack of a pentaprism or pentamirror assembly, the Sony SLT-series cameras look rather aggressive, with the popup flash housing hunched low over the top of the lens barrel. A soft, rubber pad surrounds most of the handgrip, and wraps around to the rear of the camera to cover a small, contoured thumb grip area as well.

Due to its diminutive stature, most photographers will find that the grip only accommodates two fingers, with the index finger resting on the shutter release button above, and the little finger curling beneath the bottom of the camera. This might seem a little crowded, but with the light, plastic-bodied 18-55mm kit lens, handling is nonetheless good, with the combination feeling extremely well balanced. Using larger, heavier lenses, the grip size is too tiring for single-handed shooting, so the photographer's left hand will need to serve double duty, adjusting zoom or focus while simultaneously taking up the weight of the lens itself.

Centered to the right of the lens in the photo above is the lens release button, while the depth-of-field preview button is positioned snugly at the bottom left corner of the lens mount. A small plastic panel in the handgrip conceals the infrared remote control sensor at top, and the self-timer lamp beneath. Directly beneath the shutter button and power switch is the control dial, used to make adjustments to exposure and variables and menu options.

From the top of the Sony Alpha SLT-series camera bodies, you can just see the stereo microphones, located on either side of the flash hot shoe on the sides of the viewfinder / popup flash housing, as well as the three hole grille the speaker (above the Finder/LCD button). At the top of the handgrip is the popular combination of a shutter button surrounded by a power switch, making it easy to quickly power on the camera and snap a picture with one finger. The Finder / LCD button allows the A55 and A33 to be manually switched between shooting with the electronic viewfinder or the rear LCD panel. Upper right of this is a D-Range button that provides access to Dynamic Range Optimizer and High Dynamic Range shooting options.

The Mode dial on the left shoulder is used to select the camera's operating mode. An angled panel allows you to view four buttons from either the rear or above: Menu, Movie, Exposure Compensation, and Auto-exposure Lock buttons.

You can also see the top of the mechanism for the tilt / swivel LCD panel, peeking out on either side of the electronic viewfinder. The viewfinder itself projects quite a bit from the rear of the camera, a decision that was apparently necessitated by the tight packaging of components in front, including the AF module, popup flash, hot shoe, and microphones.

When using the SLT-series cameras with a neckstrap and particularly light lenses, this might cause it to bump against your body, but with even moderately heavy lenses the camera will turn face-down even though this doesn't match the strap mount alignment, and this won't be an issue. A positive side-effect of the EVF positioning is that it makes it easier to keep your nose from smudging the LCD panel. Given the relatively tight eyepoint of the electronic viewfinder, the projection also helps prevent the photographer having to jam the camera to their face to see the entire viewfinder display.

Tilt / swivel LCD. At the rear, the 3-inch LCD dominates much of the available real-estate, and its tilt/swivel mechanism -- appearing for the first time in an Alpha camera -- can be clearly seen. The display tilts down 180 degrees and then swivels 270 degrees, allowing it to face any direction except to the front right (handgrip) quadrant. The design not only allows easy framing of high- and low-angle shots, but also allows subjects in front of the lens to see themselves -- but only when somebody's available to hold the camera. Since the display tilts downwards, it will be blocked from view when mounted on a tripod, and can't be extended beyond the 90-degree position with the camera placed on a flat surface, so the only way to use it for self-portraits is to hold the camera at arm's length. It can also be difficult to deploy and use with the camera mounted on a tripod.

On the positive side, the mechanism does allow the LCD to be folded facing inwards, providing some degree of protection against minor knocks and smudges when traveling and when you're content to use the EVF instead. The Xtra Fine LCD panel has a 921,600-dot resolution. The display also uses Sony's TruBlack technology, which couples a reinforced glass cover plate with anti-reflective film, and a resin filling that removes the air gap beneath the cover plate, which the company says improves contrast and reduces glare under harsh sunlight.

Thanks again to the relatively short stature of the SLT-series cameras, the remainder of the rear-panel controls are rather difficult to reach when shooting single-handed, even with the relatively light kit lens attached. There are only a few buttons, Function, Playback, and Delete, plus a four-way controller with a central OK button. This isn't an issue if shooting two-handed, but you do have to change your grip fairly substantially to reach any further than the top quadrant of the four-way controller. With real-estate at a premium, Sony has only provided markings on the controller for the alternate functions offered during shooting (and in the case of the Up / Display button, during playback).

Major components. (1) The Translucent mirror reflects a small percentage (~30%) of the light to the AF sensors (2) above, for uninterrupted, real-time, phase-detect autofocus. 3) Most light passes straight through the special mirror, which is more like a thin film stretched across a frame, to the main live view and imaging sensor, an Exmor APS HD CMOS design. (4) An electronic viewfinder offers 100% frame coverage, as well as image preview, and the ability to set a Display screen that's different from the LCD's display.

Translucent (pellicle) mirror. Undoubtedly the biggest story of the Sony SLT-series cameras is their use of a translucent mirror. Also known as pellicle mirror, this works by allowing most light to pass through to the imaging surface beneath, while a small portion is reflected for other purposes. Sony is not the first camera manufacturer to use a translucent mirror in an SLR-style camera, with the manual focus Canon Pellix film camera from 1965 taking that credit. The Pellix was followed by a handful of other pellicle mirror-based SLRs from Canon, Nikon, and Mamiya, largely designed for professional photographers, and manufactured in very limited production runs. It wasn't until 1989's Canon EOS RT that the first autofocus pellicle camera was released, followed by the EOS-1N RS in 1995. Fifteen years later, Sony has become the first company to resurrect the pellicle mirror for use in an interchangeable lens digital camera.

Full-time autofocus. There are several advantages to the use of a translucent mirror in place of a traditional single-lens reflex mirror mechanism. The Sony Alpha A55 and A33 use it to allow them to simultaneously provide a live view feed with full-time phase detection autofocus. Most of the light is transmitted to the image sensor, while a smaller portion is delivered to the phase detection AF sensor, where it can be used to perform focus adjustments -- even during live view, high-speed shooting, and movie recording.

Fifteen autofocus points are arrayed in an almost oval pattern.

While contrast-detection AF systems these days are much faster than they used to be, phase-detection AF generally still has the edge in terms of outright speed. It also involves less hunting around the point of focus, since phase-detection systems can determine both the focus direction and the required adjustment. On the flip side, though, contrast-detection systems generally offer more precise focusing, since the image sensor itself is responsible for confirming the point of focus, without any reliance on the lens's focus drive and AF sensor alignment being perfectly in spec.

The Sony A55 and A33 adopt a newly developed phase-detection autofocus sensor and lens module with 15 points, of which three are cross-type. AF points can be selected automatically or manually, and both predictive control (tracking) and face detection are included, although the cameras can only focus on detected faces if they fall under a phase detection point. Autofocus working range is -1 EV to +18 EV (at ISO 100 equivalent), and there's no dedicated AF assist lamp, with the A55 and A33 relying on low-power burst of internal flash or an external strobe's assist lamp for focusing in low light.

Continuous shooting. As well as allowing full-time AF during live view and movie capture, the translucent mirror design of the Sony SLT cameras brings another important advantage. During burst shooting with continuous autofocus, a traditional SLR has to drop its mirror between each frame, wait just long enough for any mirror vibration to settle, perform the AF measurement, and then raise the mirror again so that the next frame can be captured. Using a pellicle mirror, there's no reflex mirror to raise, and so the only delay required is to wait for the lens aperture to open after the exposure has been completed. For even swifter burst shooting, the aperture can be locked at either F3.5, or the maximum aperture of the lens, whichever is smaller, removing the delay required to set and reset the aperture to allow focusing between shots. The Sony A55 and A33 all offer burst shooting at up to six frames per second ordinarily, but with the aperture locked in Continuous Priority AE, the A55 offers a whopping ten frames per second, a speed only rivaled by professional DSLRs from Canon and Nikon. The Sony Alpha A33's Continuous Priority AE mode isn't quite as fast, but is still very respectable, at seven frames per second. Sony also notes that, for like framerates, the autofocus system in the SLT cameras can be active for a greater proportion of the time compared to a traditional SLR, providing more data from which to make AF tracking predictions.

Burst depth for the Sony A55 is twenty Raw or Raw+JPEG frames, while JPEG shooters can expect 35 Fine or 39 Standard-compression frames. The Sony A33 has rather lower burst shooting depth, with seven Raw or Raw+JPEG frames, and 16 Fine or 20 Standard JPEG frames in a burst; but in our experience, it clears this buffer, which is about half the size of the A55's, much faster.

One quirk of the design of the Sony A55 and A33 unfortunately conspires to make this high-speed burst shooting somewhat harder to use than would otherwise be the case. For both the ultra-speedy Continuous Priority AE mode, and the six frames per second Continuous Advance Hi mode, the live view isn't shown on the viewfinder or LCD panel. Instead, the cameras show the previously captured image. This makes it harder to follow fast-moving action, since rather than seeing what's you're trying to frame, you're effectively seeing a static slideshow of what happened around a tenth of a second earlier. This problem, incidentally, is also found on all of the SLD's we've reviewed. The Continuous Advance Lo mode, which shoots at three frames per second on the A55V and A55, or around 2.5 frames per second on the A33, does return to the live view between shots, but only briefly -- so it can still be a little hard to follow.

Image sensor and processor. Of course, the image sensor and processor are also an important part of the speed of the Sony A55 and A33, and of their image quality. The Sony SLT-A55 has a newly developed Sony Exmor APS HD CMOS image sensor, which has a total resolution of 16.7 megapixels, and an effective resolution of 16.2 megapixels. The Sony SLT-A33 also has a newly developed Exmor APS HD CMOS sensor, but with a slightly lower 14.6 megapixel total resolution, and an effective resolution of 14.2 megapixels.

Both new CMOS image sensors feature on-chip column A/D conversion, which helps increase readout speed. They also include the same on-chip analog and digital noise reduction that featured previously in the Sony A900. The SLT series cameras also have an updated BIONZ image processor, with reworked algorithms to allow their signature high-speed burst shooting, plus digital compositing and Full HD movie recording. All three SLT-series cameras offer sensitivities ranging from ISO 100 to 12,800 equivalents, and can automatically select an ISO sensitivity between ISO 100 and 1,600 equivalents.

Alpha mount. The Sony SLT-series cameras accept Alpha-mount lenses from Sony, and are backward-compatible with older Minolta or Konica Minolta A-mount lenses, allowing use of a huge range of both current and historic glass. Compared to single-lens direct view cameras -- even Sony's own NEX series -- this will likely make the new SLT-series bodies a much more attractive proposition for existing Alpha or A-mount photographers. While Alpha-mount lenses can be used on NEX cameras through a mount adapter, they lose their autofocus and in-body SteadyShot capabilities, whereas the SLT-series cameras will retain both capabilities with the same lenses. Sony rates the SteadyShot sensor shift mechanism in the Sony A55 and A33 for between 2.5 and four stops of correction.

Electronic viewfinder. Part of the camera's compact size comes due to another design decision. Unlike past pellicle mirror cameras, the Sony A55 and A33 don't provide a true optical viewfinder, but instead rely on electronic viewfinders. It's a sensible decision. The drawback to using the pellicle mirror to provide a viewfinder as past cameras did is that with most of the light being transmitted to the imaging plane, the optical viewfinder is necessarily very dim. As well as providing a viewfinder that's bright enough for low-light use, adopting an electronic viewfinder in its design has allowed Sony to increase the angle of the translucent mirror, compared to the standard 45 degrees of an SLR reflex mirror. This directs the light path for the AF sensor not only upward, but also slightly forward, allowing optimal placement to keep body size to a minimum.

While we don't currently have details on the precise viewfinder type employed by the Sony SLT-series cameras -- Sony describes it as a 0.46-inch diagonal (0.43-inch effective) Xtra Fine LCD Tru-Finder -- it clearly employs a time-multiplexed method to display red, green, and blue color information at every pixel location, suggesting it is likely a ferroelectric LCD. This differs 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 A55 and A33 as offering a 60Hz refresh rate. It's 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 A55 and A33 provides better dynamic range than most, and 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 most of the time. Sony specs the 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 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 has 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. It also has a 100% field of view, and three step automatic / manual brightness control.

Translucent mirror (redux). As noted previously, adopting a translucent mirror design has allowed Sony important benefits in terms of autofocus, burst shooting, and body size, and conceivably the removal of one more mechanical component could improve camera reliability, as well. There's no such thing as a free lunch, though, and the translucent mirror design does have some clear disadvantages as compared to existing SLR and SLD designs. Perhaps most significantly, light entering the lens is shared between the autofocus and image sensors at a fixed ratio. In the A55 and A33, about 70% of the light makes it to the imaging sensor, while 30% is reflected to the autofocus module. With a traditional SLR, all the incoming light arrives at the image sensor once the mirror is raised, and the same is true of an SLD camera whenever its shutter is open. With less light arriving at the sensor for an equivalent aperture, a translucent mirror camera must either lower its shutter speed, raise its sensitivity (and along with this, the levels of noise, or the amount processing to mitigate it), or some combination of both. An increase in sensor gain to compensate for the loss may explain why we see slightly higher noise levels from the A33 versus the A560, which share the same sensor.

Another potential issue of the translucent mirror design is that with an extra optical surface between the lens and the imager, flare could be increased, and image quality degraded. There's also another surface for dust to adhere to, and while this would be too far from the image sensor to appear as distinct specks, it could further contribute to issues with flare and reduced contrast. While manual sensor cleaning will now be a familiar process for photographers used to shooting with a digital SLR, cleaning the pellicle mirror is a total unknown. The Sony A55 and A33 provide a cleaning mode allowing the sensor to be accessed, and the pellicle mirror itself can be manually raised to facilitate this, but Sony's documentation provides no advice on cleaning the pellicle mirror itself, simply noting that the surface of the mirror shouldn't be touched.

Exposure. The Sony SLT-series cameras offer a selection of exposure modes commonplace on any DSLR, as well as several more unusual modes. These include Auto, Auto+ (Advanced Auto), Programmed AE, Aperture Priority, Shutter-speed Priority, Manual, Continuous Advance Priority AE, Sweep Panorama, Scene, and Flash Off modes. The Advanced Auto mode acts much like a regular Auto mode, taking control of most settings, but differs from the standard Auto mode in that it can also access some of Sony's more unique multi-shot modes, such as Handheld Twilight and High Dynamic Range. Continuous Advance Priority AE increases the maximum burst shooting speed as compared to the standard Continuous Advance modes, but does so by requiring the aperture be fixed near its open position. The Sweep Panorama mode can function in either 2D or 3D variants, and allows capture and in-camera stitching of multi-shot panoramic images by simply pressing the shutter button and sweeping the camera across the subject. A selection of user-friendly scene modes accessed through the Scene position include Portrait, Sports Action, Macro, Landscape, Sunset, Night view, Hand-held Twilight, and Night Portrait, and let beginners get the look they're aiming for, without needing to understand the subtleties of shutter speeds, apertures, and the like.

The Sony A55 and A33 use the image sensor itself when metering, and consider the overall image as 1,200 separate zones in performing metering calculations. Metering modes include Multi-segment, Center-weighted, and Spot, and the metering system can function from -2 EV to +17 EV (at ISO 100 equivalent with an F1.4 lens). An autoexposure lock button is provided, allowing metering to be locked from a specific portion of the subject, then the overall image reframed as desired. +/-2.0 EV of exposure compensation is available, in 1/3 EV steps. The SLT-series cameras also offer a three-frame exposure bracketing function, which allows a step size of either 1/3 or 2/3 EV between subsequent frames. Shutter speeds from 1/4,000 to 30 seconds are available, as well as a bulb position that holds the shutter open for as long as the shutter release is pressed. Flash X-sync is at 1/160 second. White balance options include auto, six presets (Daylight, Shade, Cloudy, Incandescent, Fluorescent, and Flash), plus both custom and direct color temperature (2,500 to 9,900K) options. The six presets allow +/- 3 step adjustment, and there's also a color filter setting that provides +/-9 steps of magenta / green compensation.

Flash. The Sony SLT-series cameras all include an auto-popup flash strobe with a guide number of 10 meters at ISO 100, as well as a proprietary flash hot shoe. The built-in flash has 18mm coverage, and a recycle time of four seconds. Flash modes include Auto, Auto w/ Red-eye reduction, Fill, Fill w/ Red-eye Reduction, Slow-sync, and Rear-sync. Flash metering modes include ADI and pre-flash TTL. +/-2 EV of flash exposure compensation is available, in 1/3 EV steps, and flash exposures can also be bracketed, with three frames varying by 1/3 or 2/3 EV. External strobes including the HVL-F36AM, HVL-F42AM, HVL-F56AM, and HVL-F58AM support high-speed sync and wireless shooting.

Movie mode. The Sony A55 and A33 all offer high definition interlaced video capture at up to 1,920 x 1,080 pixel resolution, commonly known as "Full HD" or "1080i." While Full HD videos are recorded using 59.94i or 50i interlaced field rates, the actual sensor data is clocked off at a frame rate of 29.97 or 25 frames per second. Using the non-standard 1,440 x 1,080 and standard definition VGA 640 x 480 pixel modes, progressive scan videos are created, matching the same actual sensor frame rates. Maximum video length is 29 minutes or two gigabytes per clip, whichever limit is reached first -- although if SteadyShot is enabled, this limit is slashed to just nine minutes per clip, likely due to sensor heating issues when using the sensor-shift stabilization mechanism. Full HD videos are recorded using 17Mbps AVCHD compression, while the lower resolutions are saved with MP4 compression, at a bitrate of 12Mbps for 1,440 x 1,080 pixel video, or 3Mbps for VGA video. Movie capture is started and stopped with a dedicated Movie button located just to the right of the electronic viewfinder, within easy reach of a thumb press.

The most unusual capability of the SLT-series cameras' video mode is enabled by their translucent mirror. The Sony A55 and A33 can continue to use phase detection autofocusing during movie recording, allowing swift adjustments to focus as your subject moves. Since standard Alpha-mount lenses are used, this focusing action is accompanied by significant levels of AF drive noise, which is clearly picked up by the camera in recorded videos. For consumers, this is likely a relatively small price to pay for sharply focused video, however, given that manually pulling focus during video capture is a difficult art to learn. If focus point selection is set to local, the Sony A55 and A33 even allow the active focus point to be changed during video capture, and it's also possible to adjust exposure compensation during recording. Also available in Movie mode are the autoexposure lock function to prevent variations in scene brightness, and white balance, creative style, AF area and metering mode functions. However, if autofocus is used, lens aperture must be controlled automatically by the camera, regardless of AF servo mode. When using manual focus, the SLT-series cameras allow manual control of aperture before video capture commences. In all cases, shutter speed and ISO sensitivity of videos is controlled automatically.

The Sony SLT-series cameras all include an internal stereo microphone, actually comprising two separate monaural microphones located on either side of the electronic viewfinder / flash housing. They can also accept external stereo microphones, courtesy of a 3.5mm jack on the left side of the camera body. Alternatively, sound recording in videos can be disabled, if preferred. The built-in speaker in the SLT-series cameras is monaural, and there's no manual control over audio recording levels.

Dust is reduced via a protective film (1) and shaken free by the sensor-shift mechanism (2).

Dust reduction. The Sony SLT cameras have a dust abatement and removal system. A charge-protection coating on the low-pass filter aims to prevent dust adhering in the first place. The sensor shift mechanism used to provide SteadyShot image stabilization also doubles as a shake mechanism to try and free stubborn dust particles that settle on the low-pass filter, although at much lower frequencies than the vibration induced by cameras using a piezoelectric element. From what we can tell, there is no strategy for keeping dust off the translucent mirror, except to blow the surface gently with air; it cannot be cleaned, and should never be touched. A fingerprint would require replacement at a service center.

Fire up the A55/A33's level gauge and you can realign yourself with the world.

Tilt level. The Sony A55 and A33 all include a dual-axis level gauge, which helps ensure level horizons and prevent converging verticals in photos. The level gauge can be shown on either the electronic viewfinder or the rear-panel LCD, but only alongside the most basic information overlay -- you can't combine the detailed display overlays with the level gauge. A clever way around it, though, is to set one viewer to the level gauge, and the other to a more informative display, since by default you can set the display modes independently. There's no way for the user to recalibrate the gauge, if they find the factory default to be inaccurate. The gauge is displayed in a style reminiscent of an aircraft attitude indicator, but with a separation of the roll and pitch indicators. When the camera is perfectly level, the pitch indicators and markings at the end of the roll indicator are illuminated in green.

Built-in GPS. Here in the US, there is only one version of the A55, and that's technically called the A55V, the version that includes a GPS. This allows both images and movies to be tagged with information regarding capture location, including latitude, longitude, altitude, receiver speed and direction, and the GPS time stamp. Movies are only tagged with information regarding the location at the start of the clip. Accuracy in our informal testing was good, with the camera determining location within fifty feet or less, but this will vary depending on the number of satellites in view at a particular time and location. The Sony A55V can display the latitude and longitude information in Playback mode, but this doesn't provide the full level of precision available in the EXIF tag, which can be accessed in Sony's software, as well as third party programs like Adobe's Photoshop.

GPS See where you were when you took your shots with the Sony A55V's built-in GPS active.

The initial GPS lock can take rather a long time to complete, on the order of several minutes, if the camera hasn't been used recently. (Again, this can depend on environmental conditions, as well as the number and position of satellites in view.) Once locked, though, we found the GPS receiver to be surprisingly powerful, able to retain a lock inside a house at a fair distance from the nearest windows. It's also possible to upload GPS-assist data to the A55V body using Sony's provided Picture Motion Browser software, which can greatly reduce the length of time required to obtain a GPS lock. This process has to be repeated roughly once per month, as the assist data is only good for so long.

User interface. Sony has retained a similar menu system in the SLT-series to that previously featured in the Alpha series DSLRs, but incorporating the new database-based Playback mode from the NEX-series SLD models. The user interface of the Sony A55 and A33 is generally clean and easy to understand, with the one major exception being the rather arbitrary segregation of still images and videos in playback mode. Switching between viewing stills and videos requires the user to either enter the menu system, or zoom out to the thumbnail view and select the appropriate tab. Neither option is immediately obvious without reading the manual, and photographers unfamiliar with the interface might believe they'd accidentally deleted the unavailable media, not realizing they were simply in the wrong viewing mode.

Special features. The Sony Alpha SLT-A55 and A33 all incorporate a variety of unusual features that have appeared previously in the company's NEX and Cyber-shot series digital cameras, including Sweep Panorama, 3D Sweep Panorama, Auto High Dynamic Range, and Handheld Twilight modes. Each of these modes automatically captures several images, microaligns them, and then combines them into one image with attributes that couldn't have been achieved in a single still.

The Sweep Panorama modes create lengthy panoramic images with a single sweep over the scene, and do a good job of automatically correcting for uneven panning, although they do sometimes show stairstepping in nearby subjects. The 3D variant is particularly unusual, in that it calculates separate left and right-eye views by comparing the positions of subjects as seen by the left and right sides of the lens. The result is saved as a multi-picture object file containing separate left- and right-eye JPEG views of the scene, for viewing on 3D displays.

Auto High Dynamic Range mode captures numerous images with varied exposure, then creates a single image with much greater dynamic range than would otherwise be possible.

Handheld Twilight mode captures a batch of high-ISO images, reducing blur from camera shake, and then averages the aligned exposures so as to reduce image noise. A new Multi-Frame NR mode acts similarly, but allows the ISO sensitivity to be selected manually, allowing use even at lower sensitivities. Of course, these effects could all be achieved in a PC with some work and know-how, but what's impressive is that they're now available with a minimum of fuss, in-camera. To ensure that even inexperienced photographers can derive benefit from these features, Sony has also created a new Auto+ exposure mode that can identify when these functions might be of use, and then enable them automatically.

Power and card. The Sony A55 uses both SD and Memory Stick Pro Duo cards, and an NP-FW50 battery.

Storage and battery. The Sony Alpha A55 and A33 offer a single flash memory card slot, but it's compatible with two memory card standards, each with various permutations. The first is Memory Stick PRO Duo / PRO-HG Duo, Sony's own proprietary media format. As an alternative for those who prefer more standardized media, Sony also supports three flavors of Secure Digital cards -- standard SD, SDHC, and SDXC.

The Sony Alpha A55V, A55 and A33 all use a 7.2V, 1020mAh InfoLITHIUM battery pack, with part number NP-FW50. Tested to the CIPA standard, the Sony Alpha A55V is expected to capture about 380 shots per charge using its LCD display, or 330 shots per charge with its electronic viewfinder. By dropping GPS support, the A55 increases battery life just slightly, to 390 shots on the LCD, or 350 with the EVF. Surprisingly, despite its lower overall spec, the A33 is rated at the lowest battery life of the trio from the same pack, with 340 LCD shots, or 270 shots with the EVF.

Sony Alpha A55/33 Shooter's Report

by Dave Etchells

Combining breakthrough translucent-mirror technology with Sony's high-speed CMOS sensor prowess, the new Sony Alpha A33 and A55 break important new ground for consumer SLRs. The Sony A55 in particular delivers higher capture speeds than any other consumer-class digital SLR, as well as true phase-detect live autofocus during video recording. Thrown in multi-shot technology (Handheld Twilight, Sweep Panorama, and Auto HDR modes) brought over from Sony's digicam line, and the new cameras offer features not found in any other SLR, regardless of price point.

I had a chance to spend a few days with a late prototype of the Sony A55 (equipped with production firmware version 1.0) prior to its release. After running a couple thousand shots through it (it does have a very fast continuous mode) I found it to be a pretty compelling camera, combining remarkable shooting speed with a host of other capabilities that really set it apart from most of the market. It's by no means perfect, but unquestionably expands the range of shooting capabilities open to consumers with average pocketbooks. Looking at just how much I found to comment on below underscores for me just how much Sony has done in the last few months. Read on for some of my thoughts on this new class of consumer SLR:

Sony A55: In the Hand

Attack of the giant hand? That's what we jokingly called these shots when we took them. Despite the disparity between the size of my hand and the camera body, the grip was still fairly comfortable.

Leaving their advanced capabilities aside, the Sony A33/A55 are also remarkably compact cameras. As we've noted elsewhere, because the mirror in the A33/55 doesn't have to be used to form a viewfinder image, it can be mounted at a steeper angle than normal, removing some thickness from the camera body as a whole (the flange-sensor distance must obviously remain the same, but there's more room in the body for the shake-reduction system and other electronics), and the space normally required for the mirror drive system could be trimmed from the sides. As a result, the A33/55 body is notably compact.

I'm always a little torn over really small camera bodies, as it can be uncomfortable to twist my longer-than-average fingers around a small handgrip. That said, I really didn't find the smallish grip on the Sony A55 too objectionable. The design of the front grip naturally encourages my middle and third fingers to curve downward, my pinkie to fold underneath the body, and to carry the weight of the camera on my middle finger, between the second and third knuckle. My customary two-handed SLR grip, with one hand on the lens' zoom ring made for a comfortable and secure hold.

Rest for your thumb The deeply sculpted thumb rest does a lot to make the grip feel secure.

Grip comfort/security is greatly aided by the deeply sculpted thumbrest on the camera's back. Combined with the textured rubber used over the whole right half of the body, it provides a very secure gripping point for my thumb, and does a lot to make up for the small size of the front grip. The rubber coating also contributes to a feel of solid build quality, by damping the body vibrations that often make small and light cameras feel tinny or cheap.

I did find the small body and grip a little problematic when shooting with a long or heavy lens, though: I spent quite a bit of time with the excellent Sony 70-200mm f/2.8 mounted on the camera, and did experience some wrist fatigue by the end of the day. Since the camera is capable of very fast live autofocus during video recording, I often found myself wanting to zoom during the recording, something that would be anathema on a conventional video-capable SLR. Doing so required that I carry more of the weight of the lens/camera assembly on my right hand, so my left could operate the zoom ring more smoothly. The result was a lot of weight for my right wrist to carry, and the small grip made it more difficult than otherwise. When shooting normally with smaller lenses, though, I never found the grip uncomfortable.

The control buttons are for the most part intelligently arranged and readily accessible, but the small space available for them on the right side of the body does mean that you need to hold the camera in your left hand to be able to access them properly: They're really too close to the right side of the camera to keep your fingers wrapped around the grip and operate the buttons with any degree of comfort. On the angled top/back panel, the EV adjust button is perfectly located, right under your thumb, with the AE lock and movie recording buttons on either side of it. The movie button does require a deliberate reach to get to, but is nonetheless easy to identify by feel when you're looking through the viewfinder; just slide your thumb over until it hits the viewfinder housing, and you'll be right on top of the movie button.

A lot of the Sony A55's settings are accessed via the Fn button, just below and the to the left of the thumb grip recess on the back of the camera. I can't think of any better place to put it, but accessing it does require loosening your grip, and therefore shifting support from your right hand to your left. Apart from that, the Fn button is in a good location, easy to find by feel: Just slide your thumb down out of its recess, and the Fn button is the first control you'll touch.

Adjusting settings via the Fn menu is generally a good experience. A very nice touch is that you can use the up/down/left/right directions of the 4-way controller to move the cursor between Fn menu items, and then use the front control dial to adjust the settings. This is nice because it lets you quickly make a number of Fn settings changes in succession, without having to drop down a menu level for each, or being forced out of the Fn menu between choices. The few exceptions to this are those items with a second level of control, such as multi-shot ISO or the tweak adjustments for white balance settings. In those cases, you need to explicitly select the menu item via the OK button, and then use the left/right keys to make the needed adjustment. The only exit at that point is to hit the OK button again, which unfortunately drops you out of the Fn menu entirely.

One nice thing about the Sony A55's electronic viewfinder is that the Fn menu is also available in the viewfinder display; you can make many camera settings without taking your eye from the viewfinder eyepiece. As I became more familiar with the camera's controls, this led to a very efficient shooting style, although it would take more than the few days I've had with the camera thus far for this to become second nature.

Sony A55 Electronic Viewfinder Display

In reviewing my experience with the Sony A55, it's interesting to find so many of my notes and so much of my attention directed to the viewfinder display. Were I not already so familiar with Sony's multi-shot exposure technology, the camera's multi-shot features would doubtless have commanded more of my attention, as they're worthy features indeed. That said, though, the Sony A55's viewfinder turned out to be absolutely integral to my experience with the camera.

Nose Relief. The Sony A55's viewfinder eyepiece projects back a bit, leaving a bit more room for your nose

Where a conventional SLR has an optical viewfinder, the Sony A33/55 substitutes an electronic display with an eyepiece attached. (An electronic viewfinder, or EVF for short.) The image for the EVF is taken from the Sony A55's main image sensor, so the camera is essentially always in "Live View" mode. Mechanically, the Sony A55's eyepiece projects out from the back of the camera a fair bit, to leave room for the camera's autofocus system in front of the EVFs micro display and viewfinder optics. I found I actually liked this rear projection, as it left a bit more room for my nose when I held the camera to my eye. Happily, the neckstrap eyelets are arranged such that the camera hangs lens-down when on a neck strap, so I had no trouble with the projecting eyepiece poking me in the chest.

I have to say up front that I've never been a fan of EVFs. While they do permit much more information overlay than conventional optical viewfinders, I've always felt that EVFs' limitations have outweighed their advantages. In particular, EVFs usually have limited sensitivity and dynamic range, not to mention low refresh rates and poor resolution when compared with the view through a conventional optical viewfinder.

Given my long-term dislike of EVFs, I was surprised to find myself as comfortable as I was with the one on the Sony A55. It by no means corrects all the ills of the genre, but does go a long way in the right direction. It still loses highlight detail in scenes with both deep shadows and strong highlights, but I found it workable most of the time. I could generally make out clouds against the sky, important for framing landscape shots. It also seemed to do pretty well under low light conditions, although as of this writing, I haven't done a lot of night photography with the camera. Still, the large pixels of the Sony A55's APS-C size sensor mean that its EVF is much more able to form a usable viewfinder image under dim lighting than is that of a typical digicam. Under really dark conditions, I'd still like to see it gain-up a bit more, though, even at the cost of slower refresh rates.

The time-multiplexed full-color RGB pixel technology generally worked well to deliver very high resolution with no gaps at all between the pixels. The only place I was aware of the EVF pixels were in diagonal strokes of letters on the various VF info readouts, or on the electronic level display, when the indicator lines were tilted. I never saw pixel jaggies when looking at the subjects I was shooting, even in the case of sharp high-contrast edges.

The one thing some users might find distracting about the Sony A55's EVF is the RGB "rainbows" you can see when either your eye, the subject, or the camera is moving rapidly. Each pixel of the display shows its red, green, and blue information sequentially, so if the viewfinder image is moving rapidly relative to your eye, you'll see red, green, and blue ghosts or trails around bright objects. I didn't notice this at all until someone pointed it out to me, but after they did, it became unreasonably annoying for a while. After a couple of days of shooting with the camera, though, I again became largely unaware of it and now have to deliberately look for it to be aware of the effect.

On the Sony A55, the EVF can serve as both shooting and playback display. As mentioned earlier, the ability to check your shots and make camera settings without taking your eye from the eyepiece leads to a slightly different and more efficient shooting style; one that encourages you to learn the camera by feel and memory, rather than looking at the controls as you press them. I've only had a few days with the camera as of this writing, but can see that greater familiarity will produce a very efficient shooting style.

A final benefit of the Sony A55's EVF is that it lets you keep the camera to your eye during video recording, something no other SLR currently offers, although some SLDs do.

I've left perhaps the most salient characteristic of the Sony AF55's EVF till last: It's huge. The view through the Sony A55's eyepiece is much more akin to that of a full-frame DSLR than that of any competing sub-frame model currently on the market. It manages this with a comfortably high eye point (and plenty of dioptric adjustment) for eyeglass wearers, at least when simply viewing the live viewfinder image itself.

Do-all EVF: The Sony A55's EVF display conveys loads of info, and the Fn menu (shown above) is accessible without taking the camera away from your eye. - But the Fn menu items do require a low eyepoint or eye movement to take in.

It turns out that the live viewfinder image doesn't cover the full screen in 3:2 aspect mode, but is normally confined to roughly the central 80% of the available display area. When you switch to the Fn menu display, though, you need to press your eye pretty close to the viewfinder eyepiece to be able to see the menu items on the left and right sides of the screen. I found that with my eyeglasses on, I had to shift my eye to the left or the right to see the menu entries on the sides, or else really mash my eyeglasses against the eyecup. Switching to 16:9 aspect ratio expands the image to fill the left and right of the EVF's LCD as well, which is also problematic for eyeglass wearers.

Interestingly, I didn't notice the unusual size of Sony A55's viewfinder display when I first picked up the camera, but I became acutely aware of its loss when I switched back to a conventional sub-frame DSLR after having shot with the Sony A55 for a day or so. The conventional DSLR suddenly felt I was looking down a tunnel, and I also found myself greatly missing the richness of the A55's viewfinder information overlays. The excellent image quality of the Sony A55's EVF did a lot to win me over to the idea of EVFs on interchangeable-lens cameras, but it was the combination of image size and informational richness that really put me over the top. Because it could appear right there in the viewfinder, rather than on the rear-panel LCD, I was surprised to see how much I came to rely on the electronic level display for keeping my landscape shots straight when there was no obvious horizon line.

Bottom line, while the Sony A55's EVF doesn't entirely conquer the challenges of its genre, it goes further in the right direction than any other I've experienced to date. Most telling is that I now find myself reluctant to give up its benefits and return to world of purely optical viewfinders once again.

Sony A55 Rear-Panel LCD

The potentially game-changing performance of the Sony A55's EVF overshadows its excellent rear-panel LCD, which is a little unfair: It's as good an LCD as is found on any other camera, and in at least one sense literally outshines them all. It's the same widescreen ~920K-dot high-resolution LCD we've seen now on a wide range of cameras from a variety of makers, but its implementation on the Sony A55 adds a couple of useful twists. First, of course, it literally twists and rotates, albeit from the bottom of the body, rather than the side. This unfortunately makes it useless for composing self-portraits with the camera mounted on a tripod, but otherwise is quite helpful for getting over-the-head and ground-level shots with ease.

A bright idea. The Sony A55's LCD screen sports a super-bright "Sunny Weather" mode. It loses some highlights, but makes the viewfinder remarkably usable in direct sunlight. Shot in direct afternoon sunlight, the sequence above gives you some idea of the effect.

The second upgrade to the Sony A55's LCD is the TruBlack technology we first saw on other recent Sony cameras. This is a combination of anti-reflective coatings and a darker mask around the LCD pixels, to keep shadow areas darker. It does seem to be an improvement over LCDs lacking it, but to my eyes, the difference isn't dramatic.

The LCD improvement I found most the most dramatically useful was the brightness settings. Set to Auto brightness, the camera will brighten or dim the LCD display in response to ambient light. This helps a good bit in bright daylight, but the display still washes out in direct sunlight. If you're shooting in bright sun, though, check out the Sony A55's "Sunny Weather" LCD brightness setting. Wow - That's areally bright display! It does blow out the top end of the display's tone curve (that is, you won't see any detail in the highlights in your images in this mode), but this is the first time I can honestly say that I had no trouble viewing a camera's LCD screen in direct sunlight. It's a really great feature, although I'm sure it further reduces the Sony A55's already-short battery life.

Sony A55 High Speed Shooting

As explained elsewhere here, a major point of the Sony A33/55's translucent mirror technology is to permit autofocus operation and image exposure to overlap each other, enabling very fast continuous burst shooting with accurate autofocus tracking. It in fact does a remarkable job of delivering 10fps full-resolution shooting speeds, although in some respects, the experience is still rather different than shooting with high-end pro SLRs with that sort of burst capability. The heart of the difference has to do with what image the Sony A55 is showing you through the viewfinder at any given moment.

High-end professional SLRs drop the mirror between exposures, providing a direct (however brief) view of the subject between shots. In contrast, in their highest-speed capture modes, the Sony A33 and A55 display a static image of the shot they've just captured. Rather than seeing interrupted glimpses of your subject in motion, the A55 displays a procession of still images, each lagging the subject motion by 1/10 second (at the highest frame rate, ~1/6 second at the highest "normal" continuous capture rate).

I'm not remotely an experienced sports shooter, so I can have trouble tracking fast-moving subjects under the best of circumstances. (I'm perpetually in awe of sports photographers who can consistently frame face shots of sports players flying down the field or court: I feel lucky if I can keep the player's whole body somewhere in the frame at 100mm. :-) Already finding tracking fast action closely challenging, I found tracking fast action closely based on a series of static images delayed by 1/10 second was quite a bit harder still. After a little practice, I got better at doing so, but I sometimes found myself resorting to tricks like keeping both eyes open while shooting, or shooting in short bursts and using the time between bursts to get the subject properly framed with full-time live view again.

I'm frankly not sure how much to make of this delayed-succession-of-still-images thing: When it comes to speed for sports shooting, the Sony A55 absolutely blows away every other DSLRs anywhere near its price bracket. It's hardly fair to compare its behavior with that high-end pro cameras costing literally five to eight times as much. (The Canon 1D Mark IV and the Nikon D3s, for example.) I was also pleasantly surprised by the extent to which I learned to compensate for this viewfinder quirk, after only a few hours of intense shooting. I suspect that experienced sports shooters would have much less trouble with subject tracking than I did, and also suspect that I'd get a whole lot more comfortable with it after spending even a few more hours shooting fast action, as the improvement I experienced in just a couple of hours was indeed pretty dramatic. Even considering these issues, though, I don't think the sequence of delayed still images seen in the Sony A55's viewfinder at all equates to the intermittent real-time view of the subject seen through a conventional high-speed SLR's viewfinder.

I found the Sony A55's AF tracking to be very fast and pretty accurate; almost too fast in some cases: If I let the central AF point wander off the subject for a fraction of a second, focus would quickly shift to the background. Many of the missed-focus shots I took were the result of this problem, versus the camera not being able to track focus quickly enough. Some high-end DSLRs have settings in their autofocus systems to adjust how quickly they respond to momentary loss of the subject. (Either from the AF point drifting off the subject, or for some interfering object passing between the subject and camera.) If Sony were able to add this capability to the A33/55, it could go a long way to reducing the number of missed shots, at least based on my experience.