Sony Alpha SLT-A57K 16.1 MP Exmor APS HD CMOS Sensor DSLR with Translucent Mirror Technology, 3D Sweep Panorama and 18-55mm Zoom Lens

by Sony

• 16.1 megapixels
• Exmor APS HD CMOS Sensor
• Translucent Mirror Technology
• High-speed 12 fps continuous shooting
• AVCHD Version 2.0 (Progressive) Full HD Movie at 60p (50p)

Product Details

• Product Dimensions: 6 x 8 x 8 inches ; 4.9 pounds
• Shipping Weight: 8 pounds (View shipping rates and policies)
• Shipping: Currently, item can be shipped only within the U.S.
• ASIN: B007ILK5LI
• Item model number: SLTA57K
• Average Customer Review: 4.8 out of 5 stars  See all reviews (113 customer reviews)
• Amazon Best Sellers Rank: #864 in Camera & Photo (See Top 100 in Camera & Photo)
  • #75 in Camera & Photo > Digital SLR Cameras
• Date first available at Amazon.com: March 12, 2012

Product Description

Style: With 18-55mm lens

From the Manufacturer

Sony Alpha SLT-A57K 16.1 MP Exmor APS HD CMOS Sensor DSLR with 18-55mm Zoom Lens, Translucent Mirror Technology and 3D Sweep Panorama (2012 Model)

• Full-time Continuous AF enabled by Translucent Mirror Technology
• 16.1 MP Exmor APS HD CMOS sensor
• BIONZ: Even more advanced image processor
• SteadyShot inside image stabilization
  
• High-speed 12 fps continuous shooting¹
  
• World's first³ Auto-Portrait Framing
• Clear Image Zoom enables high-resolution digital zoom shooting
  
• 15-point AF system with 3 cross sensors
• New Tru-Finder
  
• Enhanced Tracking Focus
  
• AVCHD Version 2.0 (Progressive) Full HD Movie at 60p (50p)²
• Intelligent Auto and Superior Auto
  
• Picture Effect
  
• Face Registration
  

Experience the Alpha SLT-A57, Sony's newest addition to their Alpha DSLR series. As the successor to the SLT-A55, the new SLT-A57 includes advanced features such as translucent mirror technology, a 16.1 MP resolution and BIONZ processor, 12 fps continuous shooting¹, Full HD movie at 60p (50p)², and the world's first³ Auto Portrait Framing. Standard zoom lenses become like telephoto zoom lenses thanks to Clear Image Zoom, which realizes a high-resolution look even when shooting with digital zoom making it dramatically easier to get the best shot.

Key Features

12 fps tele-zoom high-speed shooting

Every second, you can capture up to 12 dynamic close-ups of subjects in motion. Tele-zoom Continuous Advance Priority AE magnifies the center of the action 1.4x to bring subjects closer at a clear 8-megapixel resolution. You can also team Smart Zoom with 2x magnification for super zoomed shots (4MP, S size). The a57 also supports 10 fps continuous shooting at the camera’s highest resolution (16.1 megapixels)⁴.

15-point AF system with 3 cross sensor

The renowned precision of Sony’s 15-point AF system, previously reserved for higher grade models, ensures fast and accurate TTL phasedetection autofocusing wherever and whenever you shoot. Even when capturing moving subjects in dim lighting, the three vertically aligned cross sensors deliver accurate and reliable tracking. You can choose any of four AF area modes (Wide, Zone, Spot or Local) depending on your needs.

High sensitivity (ISO 100-16000)

The large Exmor APS HD CMOS sensor provides an extremely wide sensitivity range of 7 1/3 steps. You can use AUTO ISO (100-3200) for outstanding results in most lighting conditions or manually raise sensitivity up to ISO 16000 when lighting is low. Even at high sensitivity settings, the a57 captures every detail with natural tonal gradations and extremely low noise. This makes the a57 perfect for shooting indoor athletes at high shutter speeds without a tripod or reproducing the mood of candlelit rooms without supplemental lighting.

Full-time Continuous AF

Even at maximum continuous shooting speed and during live-view movie shooting, accelerated full-time continuous phase-detection autofocusing keeps your subject in sharp focus without the slightest delay. This remarkable AF performance, made possible by Translucent Mirror Technology, lets you effortlessly capture dramatic moments and expressions in all types of situations with professional-looking results.

Quick AF Full HD Movie

Even when shooting movies at Full HD resolution⁵, the a57 employs speedy full-time continuous phase-detection autofocusing. Most interchangeable lens cameras revert to contrast-detection AF that slowly hunts for the correct Full manual movie shooting focus when shooting movies. But the a57 delivers the same swift, accurate focusing as during still photography to capture even fast-moving subjects with clarity. You can even lock exposure, switch the focus point, enjoy digital zooming and more while shooting movies for expanded creative control.

16.1 MP resolution with Exmor APS HD CMOS sensor and BIONZ image processor

Every detail of your scene is beautifully captured by Sony’s proprietary Exmor APS HD CMOS sensor. In addition to offering impressive 16.1-effective-megapixel resolution, the a57's extra-large dimensions deliver supreme sensitivity in low-light conditions and gorgeous background defocusing effects beyond the capabilities of conventional camcorders. Moreover, dual noise reduction and enhanced BIONZ image processing ensure smooth gradations with minimal noise in low-light conditions. This means you can add a cinematic sense of drama to virtually any scene.

Release time lag

When you press the shutter button, the a57 responds in 0.05 second — a blazing speed that rivals professional cameras. Made possible by an innovative electronic front curtain shutter, this accelerated response lets you capture decisive moments with utmost confidence. The electronic front curtain shutter also produces less shutter noise and vibration than a mechanical front curtain shutter (which can be activated if desired through the MENU).

Enhanced Object Tracking

Newly improved Object Tracking utilizes powerful predictive focusing algorithms, 15 AF points in a wide focus area, blazing-fast BIONZ image processing and Sony’s original subject recognition technologies to track subjects with speed and precision. When your subject is a person, it automatically switches between face detection tracking and object tracking, depending on whether your subject is facing the camera.

AVCHD Ver. 2.0 (Progressive) Full HD 60p (50p)² movies

Create movies of amazing clarity that play extra smoothly by recording them at Full HD resolution (1920 x 1080 pixels) in the AVCHD Ver. 2.0 (Progressive) format — at the extremely high frame rate of 60 (50)² fps. You can easily download the movies to your computer for editing and recording to Blu-ray media, which is highly compatible with the AVCHD Ver. 2.0 (Progressive) codec. Sony’s lightning fast Exmor APS HD CMOS sensor and Full-time Continuous AF ensure flawless capture even at accelerated 60 (50)² fp.

Full manual movie shooting

The a57 frees you to realize your creative moviemaking vision. P/A/S/M modes (Program, Aperture Priority, Shutter Priority and Manual) let you flexibly adjust aperture and shutter speed to modify the depth of field and achieve effects like defocused backgrounds when shooting movies in the manual focusing mode. On-screen prompts provide assistance to make full manual operation quick, easy and comfortable.

Audio noise reduction

Sound is captured clearly with minimal noise thanks to a high-performance stereo microphone on the mirror housing and advanced noise reduction that effectively suppresses AF lens drive noise via innovative NR algorithm.

24p (25p)² cinema-like expression

Movies played at theaters are traditionally captured at 24 (25)² fps, creating a subtle but unmistakable look that film lovers everywhere associate with the cinema. Simply by capturing your movies at the same frame rate, in the progressive format at 24p (25p)², you can recreate this look and endow your movies with an added sense of quality and drama. This feature, together with interchangeable-lens flexibility, exceptional image quality and advanced a57 capabilities, makes it easy to achieve your moviemaking aspirations.

Interchangeable-lens freedom

Like a movie director, you can use whatever lens most effectively brings out the moment. Whether fisheye, telephoto, macro, fixed focal length or zoom lens, the a57 lets you take advantage of almost any system A-mount lens. Moreover, all of these lenses are compatible with the highspeed phase-detection AF system in the a57, enabling clear results in the most challenging conditions.

One-touch movie access

With one press of the Movie button, the a57 is ready to roll. The camera immediately enters movie recording mode even if you were shooting photographs continuously or in single-frame mode. It’s the quick and easy way to capture every moviemaking opportunity. 

Auto Portrait Framing

Simply photograph a person and new Auto Portrait Framing — the world’s first feature of its kind³ — will save an additional, optimally framed image in the vertical or horizontal orientation. The feature even recognizes the direction your subject is facing and captures more of the scene in that direction to create a more appealing balance. Auto Portrait Framing employs face detection technology and the “rule of thirds” principle to achieve this amazing feat. It also applies Sony’s proprietary By Pixel Super Resolution Technology to Clear Image Zoom to ensure trimmed images feature the same number of pixels as the original. Even close-ups provide great results thanks to highly dramatic trimming.

Clear Image Zoom

Dramatically enhanced Clear Image Zoom utilizes proprietary By Pixel Super Resolution Technology to zoom the center of your image up to 2x with nearly imperceptible degradation. It virtually doubles your zooming range to that of zoom lenses when using a standard lens or to that of super telephoto lenses when using a telephoto lens. So you can create dramatic “close-ups”, enjoy greater shooting flexibility and take more advantage of the brightness of compact single focus lenses.

Face Detection, Smile Shutter and Face Registration

You can always capture faces at their best with the a57. Face Detection technology ensures that facial features are clearly focused and skin tones are accurately reproduced by fine-tuning parameters such as exposure, white balance, flash and D-Range Optimizer. Smile Shutter captures smiles at just the right moment by automatically releasing the shutter when smiles reach the desired level, while Face Registration lets you register up to eight people for the camera to prioritize when detecting faces in groups.

Creative Style

Give your photos and movies a creative look with Creative Style settings. Depending on the scene and your creative intentions, simply select any of 6 customizable settings (Standard, Vivid, Portrait, Landscape, Sunset, or Black & White) and the camera will adjust color and other image parameters accordingly. You can also fine-tune contrast, saturation⁶ and sharpness to suit your personal preference and achieve just the right finishing touch.

Picture Effect

Ordinary scenes become extraordinary photos and movies with Picture Effect. Choose from 11 customizable modes and 15 effects that significantly increase visual impact by adjusting camera parameters and applying advanced processing techniques. Settings include HDR Painting, Richtone Monochrome, Soft Focus and a Miniature mode that makes subjects look like miniature models. You can even monitor most effects in real time while shooting.

Enhanced new Tru-Finder

The Tru-finder electronic viewfinder delivers class-leading viewing ease thanks to sharp 1440k-dot (SVGA) resolution, a 23.1mm eye-point, and a notably wide 31.9-degree viewing angle that leaves competing optical viewfinders behind. A 100% field of view combines with faithful effects previews to ensure that what you see in the viewfinder is exactly what you see in your photos and movies. So you can fine-tune every aspect of your image with confidence and achieve desired results. On-screen displays keep you informed of current camera settings.

Sweep Panorama / 3D Sweep
Panorama

Simply sweep the camera to capture breathtaking vistas. The 57 automatically records and seamlessly stitches a sequence of photos to create a spectacular image. 3D Sweep Panorama records separate right- and left-eye images to bring scenes alive when viewed on an HDMI-compliant 3D television⁸.

Auto HDR

Capture more details in the shadows and highlights by activating Auto HDR. With one press, this instant High Dynamic Range mode takes three exposures at different settings and composites the best details from each — in the highlights, mid-tones and shadows — to create a single image with wider dynamic range than any single exposure could possibly capture. You can even shoot without using a tripod. The resulting HDR image is simply breathtaking in its detail, rich color and impact.

Dynamic Range Optimizer (DRO)

DRO uses proprietary Sony technology to bring out details in the highlights and shadows and deliver naturally bright images. It can be used during continuous shooting and provides five userselectable levels of compensation.

Superior Auto mode

Relax and enjoy the convenience of point-and-shoot operation. Superior Auto mode automatically detects and analyzes shooting conditions and adjusts camera settings accordingly to achieve optimal results. It also activates advanced functions like continuous shooting if subjects are moving fast and Auto HDR if details are getting lost in the shadows and highlights. Active settings and functions are displayed on screen for easy confirmation at a glance.

Software and cloud service

Powerful, intuitive bundled software and a cloud service help you make the most of your photos and movies. Enjoy editing, file management and more.

<sub>1. In Tele-zoom Continuous Advance Priority AE mode
2. NTSC (PAL)
3. As of Decemeber 2011. Among inter-changeable-lens digital cameras.
4. Continuous shooting speed may be slower depending on shooting conditions. In Continuous Priority AE and Tele-zoom Continuous Priority AE modes, the aperture is fixed at F3.5 or the maximum aperture of the lens, whichever is smaller. Continuous shooting speed (fps) lowers when high ISO NR function is on.
5. 1920 x 1080, 60p/24p/60i (NTSC) / 50p/50i/25p (PAL).
6. Not available when B/W mode is selected.</sub>

Product Description

Sony's Alpha Series 57 is a grand way to transition from compact to DSLR photography without compromising modes of simplicity. Sony A57 extends opportunities to exercise greater creativity. From snapshots to art, photography often depends on a moment.

Even when shooting in challenging conditions, the accelerated speed, supreme sensitivity and cutting-edge functionality of the a57 ensure beautiful results. Capture the decisive moment with up to 12 fps with continuous auto focus, and lock in every detail with the 16.1 megapixel Exmor APS HD CMOS sensor the ultimate for gorgeous, high-resolution image quality, even in low lighting conditions. Whether you're stepping up to your first DSLR, or an avid enthusiast adding to your arsenal, discover the pleasure and creativity of class-above interchangeable lens photography and 1920x1080 HD moviemaking.

Take a peep through the Tru-Finder electronic viewfinder boasting 1.2 million dots for ultra-high resolution, images pop with richness, clarity and detail. Everything is easy to see with 1x magnification and 100% frame coverage. Plus, adjustable magnification optimizes visibility for those who use eyeglasses. Or you can use the brilliant 3" LCD screen.

Shoot up to 10 frames per second in incredible detail with the 16.1 megapixel Sony Exmor APS HD CMOS sensor, the camera achieves high resolution with no penalty in low-light sensitivity or sensor noise. Shoot up to an incredible 12 frames per second (in 2/3-mode) with continuous auto focus and auto exposure to capture the decisive moment. Even as a panorama.

Video Mode - AVCHD - 1920 x 1080 (60p/28Mbps/PS, 60i/24Mbps/FX, 60i/17Mbps/FH - down to VGA Built-in multimode electronic Flash (Guide# 10) SteadyShot image stabilization Advanced User Interface - Easy-to-understand Graphic Display and on-screen Help Guide User-friendly function menu Storage slot acceps Memory Stick(R) PRO D

Most Helpful Customer Reviews

79 of 80 people found the following review helpful

5.0 out of 5 stars This camera is a very nice upgrade of the already very good SLT-a55 April 25, 2012

By N Doxey

Style Name:Body Only|Amazon Verified Purchase

I have used a Sony SLT-a55 for the past year and a half and purchased a number of the Sony and Zeiss professional lens. This combination has produced very good output. Some of the finest pictures I have ever taken were with the a55. However I was annoyed that the camera was not as responsive as my a700 and the overheating problem during video recording. So I preordered the SLT-a57 March 18th and it arrived yesterday. I have only had the camera one day and I am very impressed and think the upgrade from the a55 is very good. I think the Sony SLT cameras offer an excellent feature set. I am a fan of the EVF technology. Much of my photography is done shooting stage events where the lights vary greatly across the stage. I love being able to see the adjustments of the camera setting in the EVF and shoot without needing to refer to the output on the LCD screen. What you see is what you get. I can concentrate on the subjects and wait for just the right moment in the action. I prefer to compose the scene through a VF anyway. I no longer take an OVF camera to stage events. Getting the right exposure is so easy with an SLT camera. The exposure on stage can easily vary from 1/30 to 1/640 sec at F4 depending upon the subject position relative to the lighting, especially spotlights. I no longer do any exposure bracketing. I also enjoyed the continuous focus during video recording (DLSR AF during zooming while video recording is poor), and in camera HDR feature that works very well. I do prefer an OVF camera for studio work with strobes. I have been very impressed with two other features of the SLT-a57 already. The first one is focus peaking during manually focusing. I have poor eyesight and could no longer manually focus a scene. But with the focus peaking feature my manual focusing that been restored. It is like a part of my vision has been restored. I now would buy a Sony SLT or NEX camera just for this feature alone. The other feature that appears very impressive is the clear zoom feature where the picture quality is processed and improved over what one usually gets from a digital zoom which degrades the IQ. You can zoom up to 2.8x on any lens attached to the camera. I have uploaded two pictures for you to see the magnification of my CZ 16-80 zoom lens at 80mm while lighting the subject with bounce flash (These are jpg pictures right out of the camera. Notice the knots on the beaded jug as a reference). I now will have a very nice combination with my a77 for event photography with some SSM lens. I want to thank the engineers at Sony for this feature set. In the past I felt that Sony offered some excellent lens but that each of their camera models was lacking an important feature. Now I feel that Sony has produced two excellent cameras in the SLT a77 (I bought it for its AF system (which is great) and the ability to micro adjust lens focus) and the SLT-57 model. They are very fun to use with a super feature set. They are fast, feel good in the the hand and produce very nice pictures indeed.

I tested the clear zoom feature further tonight and I think that it works as advertised which is amazing. You can digitally magnify the image up to 2.8x more while still retaining very good image quality through Sony's image enhancement feature. I included some pictures taken with my telephoto lens on the Sony a57 product page here on Amazon shot at an 8 Mp resolution. Look for yourself. I made my 200mm telephoto lens a 400mm with the push a button. There is a picture taken with my 400mm lens for comparison. It doesn't look like a gimmick to me. 4-29-12 I uploaded more pictures to the Sony SLT-a57 product page after a trip out "birding" with an 400mm lens. I think people interested in photographing wildlife should consider this camera.

Update: 5-23-12. Recently, I shot 3 stage events and I am satisfied that this camera's clear zoom feature works just as well indoors as outdoors. I was very impressed with the reach of this camera and the IQ of the images using it with a Tamron 70-200mm f 2.8 lens. I did not need to go above 1600 iso to get the shutter speeds I needed even with dancers and felt no need to do any noise removal in post proceeding. The feature set of this camera gives one so many options. Using the focus peaking feature with manual focusing more and more.

Another problem that is resolved when using the SLT-a57 when shooting stage events (formal concerts like choir or orchestra) or weddings is how quiet the shutter is. It is almost silent. In the past using a OVF camera with a moving mirror I could not get the shots I wanted for fear of causing shutter noise at a time when everyone in the audience should be quiet like when a soft song was being played or sung or when the couple is exchanging vows during the wedding. I would have to wait until a rise in volume occurred so the shutter noise would not be noticed. Often during concerts I shoot video and take still pictures (with two different cameras) at the same time. Then when I played the video back I could hear every shutter click when using the OVF camera like my a700 or a580. What a pain. Now I record video and shoot with the SLT-a57 at the same time and I do not hear the shutter in the video at all. Now I shoot whenever I want during the event. I love the freedom a quiet shutter mechanism gives me. The a77 also has a very quiet shutter as well. I am very happy with this purchase.

Update 10/27/12. I have shot with this camera for another 6 months and my satisfaction has only grown. I love the focus peaking feature for manual focusing. It is the best focus assist system for manual focusing in the world. I have shifted over to become a full manual mode shooter. I now have raised my photography to another level. Another feature have works excellent as well is sweep panorama. My sunset pictures are even better. I do agree with other people that Sony needs to improve the jpg engine of all their cameras especially with shooting in the shade. Anyway this is a class leading camera. An excellent choice for someone starting photography.

93 of 99 people found the following review helpful

5.0 out of 5 stars Great step up from the A100 April 19, 2012

By Derrick

Style Name:With 18-55mm lens

I purchased this from another retailer before it was available from Amazon. I needed it in a hurry because my A100 failed. The a57 is a very good camera but it took some getting used to.
This is my first SLT so I found the LCD viewfinder to be a bit strange at first when using a DSLR. It is very bright, and has a bit too much contrast when shooting in very bright sunlight. The LCD multiple angle live/playback/menu screen is great. Easy to see even in bright daylight. Being an SLT (single lens translucent mirror) camera, the a57 is extremely quiet when taking pictures. I use the Intelligent auto mode or the P mode most of the time as opposed to the Superior mode. I don't want the flash to pop up on its own when shooting in low light, which it does very well. All my older Minolta AF A mount lenses work well with the camera, including my Sigma 28 f2.8 macro lens. My older HVLF36am flash is completely compatible with the a57 as well.

The camera body is the same size as the a100 although a bit lighter in weight. It has a comfortable grip with room for all my fingers (no pinky hanging off like with earlier Sony DSLR models). The controls are layed out logically. There is one minor problem...it is possible to hit the movie button by accident. I would prefer a slide switch to start a movie as opposed to a button. You can eat up your memory card without even knowing what happened if not careful.

I am still a guy who misses film (I had my own color darkroom) I shot mostly 200 ASA negative film and 400 ASA in very low light conditions. So at 16 MP I feel that the A57 takes very sharp pictures in all conditions. I took a look at the a65 with its 24 MP and its brighter OLED View Finder but really did not see enough advantage to the camera to spend an extra 200 bucks. I think Sony had that in mind when they replaced the a55 with the a57. If you really want the extra MPs then 200 bucks is not bad, but you don't sacrifice much if you go with the a57. As a matter of fact you get a couple of new features with the a57 not available with the a65. One is Auto Portrait Framing. When taking a picture that captures a face, you can center and snap and the camera will automatically save a second image, re-frame the shot using the rule of thirds. Pretty cool I think. Also, if you are willing to shoot at a smaller picture size, the a57 will fire at 12 frames per second. At the largest pic size it will shoot at 10fps. Not bad for action shots. Last the a57 will shoot at 16000 ISO which for all of us old film buffs translates to a lot of pushing in the darkroom.
Not having used an SLT with electronic viewfinder before, I found out that there are things I like... such as the level indicator, and things I don't like..like too much info cluttering up the viewing area. Fortunately info displayed is optional and you can change how much you want to see.

The a57 uses the larger M size battery, the same newer battery for the a100. The a55 which the a57 is replacing uses a smaller battery, which doesn't last as long and tends to get hot as well.

The Pros of this camera are many....sharp pictures even in low light. Records movies easily (also a con)
Terrific number of auto shoot modes for all kinds of conditions including portrait re-framing and auto HDR along with multi frame exposure for low light conditions.
Uses the large M batteries.
Bright LCD multi angle live/review/menu screen.

Cons (keeping the camera from getting a full five stars)

View Finder screen has too much contrast when shooting in bright daylight, .
Easy to hit the movie button by accident...with a finger or against your chest.

The camera has some fun things I have not used yet..such as the panorama sweep mode, both 2d and 3d. Not having a 3d television I doubt that feature will get used much.

All told I look forward to using this camera for a long time to come. I will say this...I still like looking through an optical VF so my a100 is going in for repair. Using the a57 and the a100 together should allow me to do just about anything including shooting HD movies.

I am updating my review, now that I have learned a bit more about the camera and giving it five stars.

32 of 34 people found the following review helpful

5.0 out of 5 stars Fast, Quiet, Beautiful October 17, 2012

By Beka

Style Name:Body Only|Amazon Verified Purchase

Sony a57 is a really fantastic camera.
Handling of the camera is excellent and the way better than any competitor.
Its design and built quality are simply perfect, it fits in hand ideally. Not only that it's easy shooting with various settings with a57 but it's also very pleasing.
The shutter is really quiet and smooth. The electronic first curtain shutter significantly decreases sound and vibration caused by shutter mechanism.
Articulating screen is very useful and once you get used to it's a very comfortable and necessary feature to have.

Viewfinder is more than good enough, although it's not as good as OLED EVFs we have seen in high-end SLTs but it's much better than competitor's small OVFs. Most important thing is that with EVF "what you see is what you get" unlike OVFs where you have no clue what your final image is gonna be like.
One more thing, manual focusing with traditional DSLRs is a really headache, it's almost impossible to get accurate shot since the OVFs of entry-level DSLRs are ridiculously small, but with EVF you can use MF magnification or Peaking feature and never bother again how accurate focus will be.

Autofocus is really fast, unlike nikon competitors you have built-in AF motor that you can use with old excellent minolta lenses. Face detection, object tracking and AF area features are on board, so you have great ability to customize Af behavior. The shooting speed is excellent, at least twice as fast as rivals and a57 has a HUGE BUFFER SIZE (21 raw+jpeg) that takes fast shooting experience to a higher level. Video quality is outstanding, full HD 60fps is really enough for even advanced video shooters and customization of video is much better than firs generation SLTs. One downside is that if you shoot with AF you can't go wider than f3.5 and it's a shame but with excellent peaking feature you can shoot with manual focusing without any trouble.

There is not reason to talk much about image quality. It's excellent and it's not big news that 16mp sony sensor is really great. I think everyone is aware of that, since D5100 D7000 A580 A55 A35 nex-5n etc. have the same sensor. Some people claim that a57 sensor is improved over a55 but it's not true. Raw image quality is exactly the same. The one thing sony is still behind from canikon is it's jpeg engine. While White Balance colors and contrast are very good, sony a57 still fails to get as clean and detailed jpegs as the sensor allows. At low iso images are fine but at high iso NR shows its ugly head (I always keep it at Low setting).

I won't talk much about features. Clear image zoom is really gimmick and does nothing useful and auto portrait framing is only for kids under 10, it uses RULE OF THIRDS composition and crops picture, if you can't do it yourself and if you don't enjoy framing during taking pictures then why you should buy 700$ camera? So those are features that I turned off the second I got the camera and never turning them on again. Peaking, HDR, panorama and painting effect HDR are really useful features.

Before the listing of cons I want to say why this camera is better than Cnikon rivals.
WHY YOU SHOULD CHOOSE A57 OVER NIKON COMPETITORS:
A57 has much better handling experience, is much much faster, has Larger buffer size and much more features.
A57 has Built-in focus motor and Built in image stabilization so you get IS and AF with every lens you attach and with nikon you get neither of these with old lenses.
People say that nikon has the same sensors and recieves extra half stop light but come on, while nikon gathers 1.5x more light sony has steadyshot and can shoot at least 3-4 times longer with any lens, so you can get at least 2 times more light, so in most cases(except you're using stabilized lens on nikon) you get at least one stop ISO advantage with sony.
OVF technology is really old and uncomfortable and it's obvious that with SLT you have much more chance to get right shot than with SLR.
OLD minolta lenses are soo cheap and so good, you can get under 100$ some excellent lenses and have full functionality.
much better video with full-time PD autofocus.

WHY YOU SHOULD CHOOSE A57 OVER CANON COMPETITORS:
canon has fallen behind in sensor technology. Image quality of Sony sensor's are much superior to canon's.
even with extra half stop light canon iso performance is no better than sony
in terms of Dynamic range and color depth sony really puts a shame even canon's pro sensors.
much better video with full-time PD autofocus.
much better build quality, much faster, and 5 times larger raw buffer kicks canon out of game.

Cons of A57:
can't choose ISO other than power of two (x 100).
Not-so-good Jpeg engine without opportunity turning of NR.
No auto ISO in manual mode.
No hope that sony will ever do firmware upgrade.
EVF refresh rate still has to be improved.
EVF dynamic range isn't match of sensor's DR.
Aperture limitation on Video (when using AF).
Bracketing has only two options 0.3 and 0.7 EV.
Most of features doesn't work when you shoot RAW+jpeg (it's soo distracting).
ISO buttons location is far from perfect.
Why the "?" button isn't customizable and who needs the button that doesn't do anything but showing guide?

To sum up a57 is a great tool for photographer and it not only does many things but does everything well. This is a camera you'll fall in love with and this is camera that shouldn't be pared with crappy 18-55 kit lens. I highly recommend to everyone buying this camera. Cheers!