Pixiq

When Sony introduced their first DSLR (the a100) in 2006, they made a commitment to develop an entire Alpha system to include a full line of products. Since then, many cameras, lenses and accessories have been released. Each new model has retained the best of its predecessor while gaining entirely new features. The new 16.2 megapixel Alpha a55 -- and the very similar 14.2 megapixel a33 -- are definitely the most impressive in terms of new functions and engineering innovation.

Sony has completely redesigned the digital SLR by installing  a non-moving, semi-transparent reflex mirror. This component allows  70% of the light to reach the HD CMOS sensor and directs 30% up to the phase-detection AF sensor. Since a Single Lens Translucent (SLT) camera would allow little light to reach an optical viewfinder, the a55 and a33 are equipped with an electronic finder (EVF) instead. This allows for full-time, uninterrupted Live View -- in still or video capture -- on either the articulated LCD screen or the EVF. The modifications provide several additional benefits, to be discussed in a moment.

Design and Primary Features

Because the pentaprism has been eliminated, the SLT cameras are roughly 25% smaller/lighter than a conventional Alpha DSLR but include a grip that's fine for all but very large hands. Sony has retained a full range of analog controls, including a very convenient Fn button for  quick access to a dozen functions. The electronic Menu provides many additional options, in 11 screens, but you'll rarely need these after an initial setup to meet personal preferences.

The large 3" Tru-Black Xtra Fine LCD provides an exceptionally bright, contrasty and crisp display with 921,600 dot resolution. It's fully articulated so the screen to be positioned at any desired angle; this is particularly useful in Live View with the camera at a very low level or above the heads of others in a crowd. Like other recent Alpha models, the a55 and a33 provide built-in flash and image stabilizer, numerous modes, overrides and options. These include a versatile Dynamic Range Optimizer and in-camera Auto HDR (for very high dynamic range when compositing three photos).

The a55 and a33 are the first Alpha models to offer Movie mode. Many overrides can be used for video recording but the ISO, aperture and shutter speed are controlled by the camera. In manual focus only, a desired aperture can be pre-set for some depth of field control. A report published by EOSHD http://www.eoshd.com/content/337-Sony-to-add-manual-video-controls-to-NEX-and-Alpha-DSLRs indicates that Sony will soon introduce new firmware to provide more user-control in video capture. Continuous AF is available in Movie mode and it was fast and reliable with typical subjects; however, I did not shoot video clips of sports events.

The new electronic viewfinder may be the best of its type in any digital camera. It's very large, with full 100% scene coverage and ultra high 1.1x magnification. It's bright in low light, provides 1.15 million (effective) dot resolutions and displays a great deal of shooting data. A sensor detects your eye at the viewfinder and automatically activates EVF while extinguishing the LCD display to save battery power.

Other High-Tech Amenities

Before reviewing the reflex mirror technology in detail, let's take a look at the other new features that are available with the a55 and, except as stated, also with the a33. Some of these were originally developed for Sony digicams or the NEX "mirrorless" series and have finally made their way to the more serious cameras.

* High speed Continuous drive with AF can fire at a blazing 10 frames per second with the a55 and at 7fps with the a33. Unlike earlier Alpha cameras with this feature, the new models provide autofocus even at the very fast framing rates. For the most reliable light metering in High Speed Drive mode, be sure to select this feature on the mode selector dial, not only in the Fn sub menu.

* Sweep Panorama mode fires up to 25 JPEGs in a sequence while you pan the camera to the left or right. The updated Bionz processor automatically aligns all the shots, applies geometric and tonal corrections, and stitches them into a single long/narrow photo. If you pan too quickly or too slowly, the camera provides an error message; if this occurs, simply try again.

* 3D Panorama is also available, allowing the camera to produce a 3D photo by generating displaced stereo pairs of every frame; the processor integrates these to produce a 3D image in a JPEG and MPO file. This is a fun feature and the results looked great on a new Bravia 3D compatible TV.

* Digital Level Gauge, in the LCD and the EVF, indicates whether the a55/a33 is being held straight. It's useful (in both a vertical or horizontal camera orientation) with any scene that includes a line and particularly valuable in Sweep Panorama mode.

* Multi-Frame NR, in ISO Auto mode with JPEG capture, snaps six photos very quickly and composites them into one. The Bionz processor micro-aligns them to minimize the effect of any camera shake, allowing for sharp shots at surprisingly long exposures. It then composites the six shots into one, discarding most of the noise data for cleaner photos even at ISO 4000. (ISO levels up to 25,600 are available.) The fully-automatic  Handheld Twilight Scene mode is identical but overrides are not available; the camera controls all aspects of the image.

* Auto+ (Advanced) mode sets the most suitable Scene mode but it can also activate many other advanced camera features as appropriate, including  continuous shooting modes - Auto HDR, Multi-Frame NR etc.

* Built-in GPS receiver (a55 only) for tagging images as to the shooting location for viewing with a map app such as Picasaweb or Google Earth. For details about this concept, see my Geotag Your Photos with GPS Devices article http://www.pixiq.com/article/geotag-your-photos-with-gps-devices . The camera does take several minutes to triangulate in a "cold start" but its receiver is very powerful and rarely loses the satellite signal.

* 15 point phase-detection AF system array with 3 cross-type AF points  for reliability with any type of pattern. (Since phase detection autofocus is used in all modes, including Movie, there's no need for contrast-detection AF.) Face Detection and Smile Shutter are  available for snap shooting.

* Two slots for memory cards make it possible to use Memory Stick Duo and  SD/SDHC/SDXC; copying from one card to another, is not possible.

* HD Movie mode with Continuous AF is available to 1080i (interlaced Full HD) resolution in AVCHD or to 720p in MP4 format, both at 30fps. Because the reflex mirror never moves up, fast continuous, smooth full-time autofocus with phase-detection technology is available. (This is a first for a DSLR camera.) Audio recording is mono but the cameras accept an external stereo mic for better quality, such as the Sony ECM-ALST1 or ECM-CG50.

Video clips are impressive in both MPEG-4 and AVCHD format, thanks to the large pixels, the excellent sensor and sophisticated processor. The NEX cameras provide similar quality but the a55/a33 is definitely better than a digicam with a tiny sensor and miniscule photosites (pixels).

SLT Technology Benefits

Sony was not the first to eliminate reflex mirror up/down action. Canon used a similar (pellicle mirror) concept as early as 1965 as discussed in a Wikipedia article http://en.wikipedia.org/wiki/Pellicle_mirror . The problem was that the viewfinder image was quite dim so Canon abandoned this technology after the EOS RT was made in 1989. Viewfinder brightness is not an issue with the a55/a33 because the electronic finder receives the preview "feed" from the CMOS imaging sensor. And there are other benefits to the fixed mirror and EVF combination.  

* Autofocus is maintained at all times since the reflex mirror never blocks the light path. That allows for phase-detection AF even in Movie mode. (This type of AF is faster than contrast-detection AF, especially in low light). As well, in action photography, the camera can continue to focus without any interruption.

* When shooting a series of still photos, the live preview (in the LCD or EVF) is never interrupted by blackout due to reflex mirror action.   

* The live preview in the EVF allows you to see the effect that will be provided by various exposure compensation, WB and Creative Style settings.

* More data displays are possible with an EVF than with an optical viewfinder.

* The electronic viewfinder eliminates the need to compose on the LCD, even in  Movie or Sweep Panorama Mode. That's ideal on sunny days when glare can obscure the external display. (No other DSLR provides this feature.)

* The high resolution EVF can also be used for viewing images in playback mode.

Since the electronic viewfinder is much better than the ones in cameras with a built-in lens, it's definitely suitable even for serious photo enthusiasts. Granted, the EVF does black out for a split second when the camera's buffer memory is full but that usually occurs only after shooting numerous photos at 10 fps. And some users report seeing a rainbow effect (colored streaks) when moving their eye around the viewfinder but I was never aware of this effect. 

Note: There is one potential problem with an electronic viewfinder when shooting a long series of photos of erratically moving action in high speed Drive mode. The displays shows the last shot that was taken. Instead of a real time view, it displays where the subject was located about 1/10sec. earlier. And yet, I rarely had any difficulty keeping the competitors framed during rodeo events.

Some long-time photographers will always prefer an optical finder especially if they try the EVF for only a few minutes. I was able to shoot over a thousand frames with it, during a Sony press tour in Wyoming but also in Utah and closer to home, and I become an EVF convert. While a traditional finder provides better highlight and shadow detail, the other benefits of Sony's new finder are significant.

Performance and Image Quality

The a55 was fast in most aspects. Start-up time was about 1 second. When using a fast Class 6 or Class 10 memory card, I was able to take a dozen Fine JPEGs in a burst and the camera was usually ready for a few more. Processing of many RAW or RAW+JPEG photos -- or JPEGs made at 10 fps -- was not as quick. After I released the shutter button, the camera "froze" while the processor was dumping data to the memory card. While I did not conduct scientific testing vs. other enthusiast-level DSLRs, the a55 did seem to be slower than average in this single aspect.   

Autofocus was fast and accurate when rodeo competitors approached my position as long as the focus detection point remained on the subject.  (For the best Tracking AF, I used only the central AF point.) It was less reliable with go-karts barreling toward my position at high speed, moving erratically and accelerating rapidly. At 6 fps -- and especially at 10fps -- the AF system was not always able to predict the subject's position at the instant of exposure. As well, in 10fps mode, the camera sets the aperture/shutter speed and ISO; at times, the shutter speed was a bit too long to fully freeze the motion.

The a55 tended to overexpose, easily solved with a -1/3 or -2/3 compensation setting. Well-exposed low ISO JPEGs are outstanding, suitable for making huge prints thanks to remarkably high resolution. The RAW captures were even better when I turned Noise Reduction Off in the Sony Image Data Converter software. By ISO 800, Noise Reduction began smearing fine details but my best shots still made very nice 11x15" prints. Even photos made at ISO 3200 allowed me to make decent letter size prints after applying the Smart Sharpen filter in Photoshop or Elements.

Note: The Multi-Shot NR and Handheld Twilight mode (discussed earlier) provide amazingly clean JPEGs at high ISO levels. One of these modes, in JPEG capture only, is definitely the best choice for stunning quality in low light when not using flash.

The Bottom Line

The Single Lens Translucent cameras are not merely evolutionary, or simply upgrades over the previous Alpha DSLRs. The new technology is revolutionary and it offers valuable benefits. Adding the best features from other types of Sony cameras also makes the a55/a33 particularly versatile. My own favorite amenities included Sweep Panorama, Multi-Frame NR for low light photography, fast AF in Movie mode, and the high magnification 100% EVF.

The a55 should be a strong contender among enthusiast-level DSLRs with its 16.2 MP resolution, excellent CMOS sensor, built-in GPS receiver and 10 frame per second mode with autofocus. The latter is great whenever you want to capture the perfect instant; it's available with some other DSLRs too but those cost $5000+. Anyone on a tight budget should love the 14.2 megapixel a33, with the same features, but without GPS and with a slower (but still fast) 7 fps drive mode. Aside from speed, versatility and very fine image quality, both cameras are also convenient to operate. 

If you're considering a fast, high tech, multi-talented, high resolution DSLR, be sure to ask for a demo of the Sony Alpha a33 or a55 while comparison shopping. Get a feel for the electronic viewfinder, but remember that it will take longer to become fully comfortable with this feature. Try the high speed drive and Multi-Frame NR mode especially, using your own memory card. If my experience is any indicator, you'll be favorable impressed with the potential value of Sony's unique features and entirely new technology.

Specifications: For additional information and a detailed Specs list visit the Sony Web site for the a55 http://www.sonystyle.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10151&catalogId=10551&langId=-1&productId=8198552921666254677 or for the a33 http://www.sonystyle.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10551&storeId=10151&langId=-1&productId=8198552921666254673

Also see Sony's video demo of the camera at http://www.facebook.com/video/video.php?v=10150251898450062

Prices: a55, $750 body only or $850 with an 18-55mm lens. a33, $650, body only or $750 with lens.