Sony's latest Single Lens Transparent ('SLT') camera - the Alpha A55 - adds GPS and a super-fast 10fps burst rate. Is the Sony A55 the dawn of a new digital camera revolution?
The first of two ‘SLT’ cameras to be released, the Sony Alpha A55 really is something quite special. Unlike a DSLR, Sony’s latest A55 creation uses translucent mirror technology that enables super-fast phase-detection AF during live view, plus a rapid 10fps continuous shooting mode. And all for less than £700. Will the Alpha A55 and, indeed, this new technology see off its DSLR rivals?
Sony Alpha A55 review – Features
At present, the A55 is the highest-specified SLT in the Alpha stable, though there’s the promise of more to come in the future. With a 16.2-megapixel APS HD CMOS sensor at its heart, it’s possible to shoot high-resolution images up to ISO 12,800, with the option to record 1080i HD movies as well. Added to this is Sony’s SteadyShot Inside image stabilisation system, whereby the sensor is designed to shift in order to counter shake from whatever lens (Sony A-mount or older Konica/Minolta-fit) is attached to the front.
Where the A55 truly excels is with its super-fast shooting capability. Whereas most cameras at this level are capable of shooting a few frames per second, their autofocus systems tend not to be able to predict focus or track moving subjects. This is where the A55 is clearly different: its translucent mirror doesn’t need to move when taking a shot, thus reducing the amount of mechanical movement and sync with the shutter to allow for a super-fast 10fps frames per second in live view mode. In addition, it also has the ability to continuously re-focus for impressive accuracy. The AF system offers a 15-point array with three cross-type sensors towards the centre for more accurate use in both portrait and landscape orientations.
As phase-detection autofocus is available to use in live view mode (unlike other DSLRs), the 1080i movie recording mode is able to take great advantage of this as the A55’s rapid, accurate and a truly continuous AF can easily glide between subjects.
Built into the body there’s a GPS (Global Positioning Satellite) unit that captures location-based data and attaches this information to the EXIF data of each shot. This can be used to ‘geotag’ images (i.e. place where each shot was taken in order of physical location), which is particularly useful for ordering projects, re-locating locations. Many up-to-date websites and programs can utilise the data intelligently in a number of ways too.
However, the one ‘drawback’ (as some may see it) to the A55 is that it doesn’t have an optical viewfinder. Instead, an electronic viewfinder (sometimes abbreviated to ‘EVF’) sits in its place. An optical viewfinder would not be practical due to the camera’s construction (not enough light would reach it for a bright preview), and this is the price paid for garnering the advantages of a SLT system over a standard DSLR. The A55’s EVF is a 1.15 million-dot unit that offers an impressive 100% field of view to ensure that what you see in the frame precisely correlates to the image produced. On the rear of the camera there’s a 3in, 920k-dot (VGA) LCD screen that can also be used to compose images, and this is bracket-mounted to allow for a variety of vertical and horizontal rotations.
In addition to all the manual modes you could want, the A55 also features an Auto+ option for more simple point-and-shoot operation, as well as a variety of Scene modes. D-Range Optimiser, Handheld Twilight, Sweep Panorama and HDR (High Dynamic Range) Auto modes and the standard Creative Styles set found across the Alpha range also feature.
How Single Lens Translucent Works
Sony Alpha A33 & A55 – How ‘Single Lens Translucent’ Works:
The best way to explain how a translucent mirror system works is to compare it side by side to a DSLR system’s operation.
In a DSLR camera the light enters from the lens and bounces off the camera’s mirror into an AF sensor for fast phase-detection autofocus. Simultaneously, light also bounces into a pentaprism that in turn feeds a preview image to the eye via an optical viewfinder (the pentaprism is there to flip the image from upside down and back to front to the usual way we see). Once the image is framed and the focus set a full shutter press will flip the mirror upwards and out of the way before the shutter itself fires to expose the image sensor (for the time period the shutter is set at) for the final image capture.
An ‘SLT’ camera, as Sony is naming the A55, also has a mirror construction – but, as this is translucent, 70% of light can permanently pass through, thus eradicating the need for the mirror to move at all during an exposure. Without the need for this slow mechanical movement it’s only the shutter that fires to make an exposure – and this can happen much more frequently, hence the A55’s super-fast 10fps shooting. The 30% of light that bounces off the mirror is still available to reach an AF sensor for continuous phase-detection autofocus during live view mode – the first time this has been possible in a digital camera (including the A33 that was released alongside the A55).
This way of doing things does not lend itself to an optical viewfinder due to the lack of light that could hypothetically reach it – this is why the A55 features a built-in electronic viewfinder, or EVF, instead.
Design & Performance
Sony Alpha A55 review – Design
Because the A55’s construction differs from a traditional DSLR it is slightly smaller in size, though not drastically so. Although this may be a draw for some prospective users, there’s still plenty of body to grip hold of.
Apart from this, the A55’s overall external appearance doesn’t wildly differ from a regular DSLR – a mode dial to the top left can be quickly accessed and adjusted, while the Fn (Function) button on the rear of the camera is used for quick access to the majority of the most used settings. The back of the camera also offers a standard d-pad arrangement for menu navigation purposes, with a variety of one-touch buttons dotted about elsewhere to control movie, exposure compensation, exposure lock, D-Range Optimiser and depth-of-field preview.
The menu system is easy to understand, and with no need to scroll through pages of sub-menus locating various options is relatively easy.
Sony Alpha A55 review – Performance
Despite being the first-generation of a new breed of camera the A55 clearly takes on board Sony’s ongoing experience in the DSLR sector. As such it works remarkably well and is by and large the very same as using a DSLR camera for the most part.
If an electronic viewfinder really isn’t for you then the A55 may fall at the last hurdle. However, to dismiss the A55’s EVF out of hand could be a naïve mistake as it offers a whole host of functionality. At 1.15-million dots the resolution equates to 800×480 pixels which, although not dramatically resolute, is up there with the best available at the time of writing. Add the benefit of light-up AF points that can be completely turned on or off as desired, a dual-axis level that can be shown when lining up shots to avoid converging lines, a grid overlay and an active histogram and there’s lots to shout about. Its field of view is a true 100% too, meaning what you compose is what you get. However, pushing the scales back the other way a little, the EVF’s one major flaw is low-light performance: image preview can blur and lag, be noticeably noisy and will often lack the crispness and detail that an optical viewfinder would otherwise be able to deliver. Without seeing the EVF in action it’s hard to decide whether it’s right for you or not, so getting down to a photo store and giving it a go is certainly advisable. Should you choose to use the rear LCD screen instead of the EVF to compose your images with, the 3in, 920k-dot screen is set in a 16:9 widescreen ratio. As such the usual 3:2 stills ratio won’t fill the entirety of the screen.
The new 15-point AF system has three cross-type sensors towards the centre arranged for added sensitivity in both portrait and landscape orientation. Focus is quick off the mark, though the arrangement of the AF-points favours the centre of the frame, which leaves a lot of space towards the edges that aren’t catered for. Also, shooting objects of low contrast caused issues, while the lack of an AF-assist lamp means no additional continuous light for use in darker conditions (only the flash can be used for pre-flash).
Where the A55’s strengths really lie are with its phenomenal speed. The 10fps burst mode only operates in Speed Priority mode, which is like an Auto mode for super-fast shooting. If you want to take full control of the camera then all other modes offer a continuous burst of a still-impressive 6fps by adjusting the drive mode accordingly. The clear benefit of this burst is just how good the camera is at tracking a moving subject while maintaining focus – regardless of whether a subject is moving away or towards the camera at speed, the A55 delivers the goods. The fact that this can be achieved through the viewfinder or by utilising the same autofocus system in live view opens up a variety of different possibilities in use, the likes of which a regular DSLR’s live view system wouldn’t even begin to match.
Continuous shooting is matched with a relatively generous buffer size too. This test recorded 18 Raw + JPEG shots taken in a row at 10fps with no letup in speed whatsoever. Compare this to the 10 frames the A55’s younger sibling, the Alpha A33, can take at 7fps and this is one of the notable differences between the two cameras. However, once the buffer is writing it can take rather a long time to clear, with those 18 Raw + JPEG shots taking some 45 seconds before the SD-write lamp switched off. Fortunately the camera is still operable during this time period, so it’s of little consequence for most shooting scenarios.
Sony Alpha A55 review – Image Quality
Sony A55 review – Tone & Exposure
Despite only 70% of available light reaching the sensor there’s no discernable difference in image quality compared to a DSLR with a similar sensor size and resolution. The loss of 30% of light only equates to 1/3rd of a stop and the processing adjusts for this accordingly so that the output is still in accordance with the same ISO standard.
Exposure is generally accurate and avoids overexposure in most situations. However there is an issue with ghosting that, despite only affecting a tiny percentage of images, does need pointing out. Ghosting gets its name from a secondary, ghost-like image that can appear within a single frame. In the case of the A55 this is not at all severe and only clipped-out (overexposed) highlight areas of a considerably small size will show a ghost in very close proximity. There are very few cases when this will be a problem as the highlight area needs to be limited to the equivalent of a few pixels to show, though the issue is still there.
Tonally images on the camera’s LCD screen appear more punchy and vibrant than when revealed on a computer screen.
Sony A55 review – Colour & White Balance
Auto White Balance works well, despite the occasional outdoor cool cast and indoor warm cast. Colour itself appears more punchy when viewed on the camera’s LCD, but lacks quite the same level of contrast when viewed on a computer screen. There is also a slight colour shift between the LCD and a balanced monitor.
For further control there are a variety of Creative Style options to chose from that include: Vivid, Sunset, Portrait and Black & White.
Sony A55 review – Sharpness & Detail
The A55 resolves detail well at lower ISO settings, but at higher ISO sensitivities detail can be lacking. The 18-55mm kit lens performs adequately enough, although better quality lenses (such as the 50mm f/1.4 Sigma we used) will obviously yield better results.
Sony A55 review – RAW vs JPEG
In the box is a copy of Sony’s Image Data Converter SR software that can be used to convert the ARW-format Raw files.
The difference between ARW and JPEG is negligible at first glance, but the lack of noise reduction employed in the Raw file means more overall detail. This becomes progressively more noticeable from ISO 800 and upwards, and is particularly prominent at the highest sensitivities.
Sony A55 review – ISO Quality & Image Noise
Image noise is no problem when shooting ISO 100-400, but begins to appear from ISO 800 onwards. Between ISO 800-1600, images are still of a good quality but detail does begins to diminish – especially when viewing images at 100%.
ISO 3200 is still usable, and although 6400-12,800 show a considerable loss of detail and the presence of luminance noise, the A55’s noise reduction processing does a good job of keeping colour noise at bay, even in the shadow areas.
Movie/Video Mode & Quality
Sony Alpha A55 review – Movie/Video Mode & Quality
Sony A55 review – Movie/Video Quality
When shooting in AVCHD final movie quality is very impressive indeed. Although clips are shot in a 1920×1080 pixel interlaced format (i.e. half the lines in one pass, the other half in the second pass), the level of detail is still very impressive and the data rate is a massive 74Mbit/sec. One small issue is when not using a formatted card it will become nigh-on impossible to extract your files from the camera (as AVCHD files have to be processed using software such as iMovie or Windows Movie Maker).
There is a secondary option to shoot in MP4, which is captured at 1440×1080 pixels and then ‘upscaled’ to fit the usual 16:9 ratio. The quality here is less impressive though, with a much lower data rate. However, the files are smaller and won’t need processing when offloading from camera.
Sony A55 review – Movie/Video Record Time
Maximum record time is up to 29mins or 2GB, though the AVCHD format is so packed full of data that you’ll only manage a few minutes before the largest file size is reached. This is the same for AVCHD 1080i, and MP4 AVC and VGA.
As a number of reports have suggested and Sony Japan itself has now confirmed, the sensor overheats when using SteadyShot while recording. This isn’t at all surprising given the amount of work the sensor is doing, and with a clip length topping out at around 7mins this is still a fairly long time to be able to shoot (how often would a longer clip length be utilised?).
Sony A55 review – Movie/Video Focusing Modes
Focusing during movie recording is where the A55 both wins and loses. On the one hand the continuous focus is outstandingly good and will effortlessly snap between one subject and the
next without misjudging focus at all.
The only qualm with this is the lack of overall user control, as there’s no capacity to lock the focus (bar clunkily flipping the lens’ AF/MF switch). Such a feature would be useful in some situations, for example when the camera is focused on a stationary subject and another subject walks through the frame causing the camera to switch focus to the new subject. This won’t always be desired and a greater level of detail in control here would make all the difference. Many DSLRs and Micro System Cameras offer a one-touch button to re-focus and this single-point fixed focus isn’t possible with the A55.
Sony A55 review – Movie/Video Manual Control
There’s no true fully manual control when shooting in movie mode, although the degree of control in Program mode should prove ample for most situations. During recording it’s possible to use both exposure compensation and exposure lock in real time, which can prove considerably useful. However, limitations with focus modes, aperture selection and a fixed 25fps frame rate mean there’s some room for improvement.
Sony A55 review – Movie/Video Sound
The kit lens can be rather noisy when whizzing between different focal lengths and the camera will pick up these sounds. Thankfully there’s
a 3.5mm mic jack for an external microphone
to be used should you please.
The sound quality is otherwise very good (partly dependent on which mic you choose to use) and rendered as AAC Stereo.
Value & Verdict
Sony Alpha A55 review – Value & Verdict
Sony A55 review – Value
At the £700 price point there’s nothing else on the market that can match the 10fps continuous focus – a notable benefit of the SLT technology that even out-performs (in terms of speed, at least) the Nikon D300s. However, there are some fairly big differences in the level of control the A55 offers compared to what a professional DSLR can provide, but the difference in prices more than justifies this.
Those looking for super-fast shooting will be suitably impressed and when considering the high resolution, image stabilisation, GPS and movie mode, the A55 and, indeed, the A33 look to be among the most rewarding and valuable models available.
Sony A55 review – Verdict
Sony’s new SLT technology is highly impressive and offers a cost-effective way to achieve super-fast autofocus with an impressive burst rate. Indeed this could be the first stepping-stone to the end of traditional DSLRs as we know them.
Although the electronic viewfinder may not be to everyone’s tastes and isn’t especially impressive in low light, these are relatively small hurdles when considering just what the A55 can do. In any case, we’re sure future models will improve the EVF’s performance in low-light.
This is a very innovative camera and there is currently nothing else out there (save the Sony A33) that can compete
on quite the same level. The autofocus
in HD movie mode takes away many
of the issues that DSLR cameras would otherwise suffer from, while general performance is impressive. Additional touches, such as the built-in GPS are
a further nod towards just how technologically advanced the A55 is.
Overall this is quite an achievement that gets a big thumbs up.
Daylight, Shade, Cloudy, Incandescent, Fluorescent, Flash, Setting the color temperature
Yes, ±2EV (in 1/3 stops)
Fine or Standard (JPEG)
4912 x 3264
3in, 921k-dot, tilt-angle, TruBlack LCD
2500 – 9900 Kelvin
15-point system with 3 cross-type sensors
Yes, 3 frames, Selectable 2 steps
16.2 megapixels Exmor APS HD CMOS sensor
1200-zone evaluative metering
Yes, Charge protection coating on Low-Pass Filter and electromagnetic vibration mechanism
Yes, sensor-based Super SteadyShot
Yes, 1080i HD capture
P, A, S, M, Continuous Advance Priority AE, Sweep Panorama, Scene, Flash Off, Auto, Auto+
441g (no battery or card)
HDMI (c-type), USB (standard
Rechargeable li-ion battery
Raw, JPEG, RAW + JPEG
124.4 x 92 x 84.7mm
30 – 1/4000th second (plus Bulb)
Single, Automatic, Continuous, Manual Focus
Single, Continuous, 10 seconds and 2 seconds Self-timer, max 7fps in Continuous Advance Priority AE, max 6fps in Drive Mode
sRGB, Adobe RGB