Sony Alpha A55 £800

2nd Mar 2011 | 11:00

Sony Alpha A55

The first DSLR to use a translucent mirror is part of a new breed of digital cameras

TechRadar rating:

3 stars

Like:

Fast live view AF system; Good features; Articulated screen; Good image quality

Dislike:

Live view blackout after shooting; Fast memory cards are a must; Small buffer

Sony Alpha A55: Overview

Sony isn't one to be left behind when it comes to the latest crazes. Its NEX cameras were released earlier in the year in response to other manufacturer's compact mirrorless camera offerings. Now the company has moved to introduce a new genere of SLR-style cameras with electronic viewfinders.

This is where the Sony A55 body fits in, being an electronic viewfinder camera that can accept the range of Sony Alpha-mount lenses. It's not quite the same as the offerings you'll find from Panasonic digital cameras, Samsung et al, as it's not a mirrorless camera.

Interestingly Sony has chosen to implement a translucent mirror system in the Sony A55 body, which allows for fast phase detection autofocus during live-view, and also while recording video. Translucent mirrors are nothing new, and were first seen in Canon's Pellix 35mm SLR back in the mid-1960s, although Sony's implementation of this technology is quite novel.

As the mirror is translucent, it remains in the optical path at all times, directing a third of the light to the autofocus sensor, whilst allowing the other two thirds to pass through to the imaging sensor. The advantage of this design is that the camera can use the phase detection AF system in live view mode instead of the slower contrast detection system that is employed by other cameras when images are composed on screen. It also allows the camera to be more lightweight and avoids the problem of mirror-induced vibrations.

Unfortunately as the mirror causes a loss of light available for imaging, the design will mean slightly higher sensitivities will be required for the same exposure, which may result in grainier pictures. In addition, the loss of light would mean that an optical viewfinder would be quite dim, so Sony has opted to employ an electronic viewfinder (EVF) in the Alpha 55 and Alpha 33.

With the Sony A55 price at £800 (including the 18-55mm kit lens) at its launch, the current Sony A55 price on the high street has already dropped to around £700, which is a similar price tag to SLR cameras geared towards the enthusiast, or a beginner after a few more features. Other cameras in the Sony A55 price bracket include the Nikon D90 or the Canon EOS 550D which offer many similar features, such as a high resolution sensor and HD video, but have optical viewfinders.

Sony Alpha A55: Body, build quality and handling

Although the external design on the Sony A55 body looks very similar to conventional SLR cameras, it is noticeably smaller and lighter than similar cameras, weighing only 441g.

Sony has managed to achieve this without compromising the build quality on the Alpha 55 body. Although the Sony A55 body is constructed from high-quality plastics, they are rigid enough and feel as though they could take a decent amount of use and abuse. Soft rubber has been fitted to the rear and the finger grip on the front, which makes handling the camera a pleasantly tactile experience.

Using an electronic viewfinder (EVF) rather than a pentaprism may not be to everyone's taste but it is one of the better EVFs around, with a resolution of 921,600 dots providing a clear view of the scene. Even though the view is clear, it is no substitute for a conventional optical viewfinder when it comes to confirming focus. Rather annoyingly the rubber eye-cup, doesn't remain fitted for long, deciding to go off for a wander every time something brushes up against it.

Helpfully, a proximity sensor under the eyepiece automatically switches between the 3-inch swivel screen and the EVF, making the change from one to the other virtually seamless. The placement of the Sony A55 sensor means it is sometimes possible to accidentally trick the camera into switching to the viewfinder when adjusting the screen, or operating some menu functions.

Despite its diminutive stature, the Sony A55 body controls are well-laid out and don't feel at all cramped with most common controls such as ISO and exposure compensation being within easy reach. As the camera is optimised for live-view, the layout has been optimised for use with one hand, which is made more than possible by the lightweight Sony A55 body.

The menu system is simple to follow, with photographic functions such as flash compensation and picture styles being separated from general camera settings like image quality and GPS settings. Autofocus has its own dedicated button in the centre of the control pad, which speeds selecting one of the 15 focusing points.

Sony Alpha A55: Controls and features

Having a 3-inch articulated swivel screen is an incredibly useful tool when shooting out and about. As the screen can be adjusted to pretty much any angle it will save countless muddy knees on those occasions when you wish to shoot from a low angle. This coupled with the fast phase detection autofocus makes for a very flexible system, allowing your creativity to go beyond what can be seen at eye-level.

Fifteen autofocus (AF) points, of which three are cross-type, can either be selected individually, or set as a wide area providing plenty of options for most shooting scenarios. In use the AF system is quick and accurate, most of the time, but it can struggle to keep up with moving subjects and will occasionally miss-focus altogether. Still, for the most part it is a reliable system, making the live view feature feel truly integrated, instead of a bolt on afterthought.

Previous cameras with translucent mirrors, such as the Canon EOS 1N RS, used them to allow fast continuous shooting speeds with no viewfinder blackout. The Sony Alpha 55 certainly achieves the fast shooting, with a maximum continuous shooting rate of 10 frames per second, but during shooting the screen freezes after each frame and blacks out completely for a while whilst the images are written to the card in any of the manual exposure modes.

This blackout time can be quite considerable, especially if shooting raw images, or even worse if shooting raw and JPEG files simultaneously. The only way around this is to select the automatic 10 frames per second mode from the dial on top of the Sony A55 body. This mode reduces the screen blackout and allows continuous AF to be used. Unfortunately it also removes the ability to adjust the shutter speed or aperture, which may be an issue in some situations.

This novel mirror also allows continuous AF during Sony A55 video recording, allowing the camera to keep up with moving subjects. In principle this is a great feature for those using the camera for video, although it it worth noting that the AF speed is much reduced during video recording and that the sound made by the lens can be heard in the recordings.

The quality of the Sony A55 video is excellent, with clear, crisp footage being produced, even in low light conditions. As it is full HD, your Sony A55 video will look great on your HD television and the AVCHD format used for recording Sony A55 video is widely supported.


The usual array of scene modes and picture styles are all included as well as a few interesting additions. A sweep panorama function makes taking a wider view quite straightforward as you simply move the camera in the direction the camera requests. It then takes pictures continuously and merges them automatically. An automatic HDR function is also provided, allowing shots up to six stops apart to be merged into one image with increased dynamic range.

Sony Alpha A55: Image quality

Metering is provided by the main imaging sensor and the image area is separated into 1200 zones during evaluative metering. Evenly lit scenes tend to be exposed a little on the bright side, leading to washed out colours, so it pays to keep an eye on the histogram and apply compensation accordingly. Centre weighted and spot metering modes are also provided. A circle showing the area the light reading is taken from is shown on-screen during spot metering, which is a nice touch.

Colours are vibrant, even when using the standard picture style. If more colour is required then the landscape and vivid styles should satisfy most. Even when not using the dynamic range optimiser feature, the Sony A55 produces images with excellent dynamic range. Where highlights do blow out, the roll off into white is smooth and subtle, giving a pleasant film-like appearance.

As the translucent mirror reduces the amount of light available for imaging by a third, the sensor really needs to be good at controlling noise, and luckily it is. There are no significant signs of noise in the shadows until ISO 1600 and even ISO 12800 should be very usable for all but the largest print sizes.

Images produced by the camera appear a little softer than images produced by other contemporary cameras and a little extra sharpening, either in-camera, or afterwards in image editing software may be required subject to taste.

Sony Alpha A55 ISO performance

JPEGs

ISO 100

Sony A55 Review: 0.8secs at f/11, ISO 100

ISO 100

Sony A55 Review: ISO 100 (Click to view full size)

ISO 200

Sony A55 Review: ISO 200 (Click to view full size)

ISO 400

Sony A55 Review: ISO 400 (Click to view full size)

ISO 800

Sony A55 Review: ISO 800 (Click to view full size)

ISO 1600

Sony A55 Review: ISO 1600 (Click to view full size)

ISO 3200

Sony A55 Review: ISO 3200 (Click to view full size)

ISO 6400

Sony A55 Review: ISO 6400 (Click to view full size)

ISO 12800

Sony A55 Review: ISO 12,800 (Click to view full size)

Raw Files

ISO 100 raw

Sony A55 Review: ISO 100 (Click to view full size)

ISO 200 raw

Sony A55 Review: ISO 200 (Click to view full size)

ISO 400 raw

Sony A55 Review: ISO 400 (Click to view full size)

ISO 800 raw

Sony A55 Review: ISO 800 (Click to view full size)

ISO 1600 raw

Sony A55 Review: ISO 1600 (Click to view full size)

ISO 3200 raw

Sony A55 Review: ISO 3200 (Click to view full size)

ISO 6400 raw

Sony A55 Review: ISO 6400 (Click to view full size)

ISO 12800

Sony A55 Review: ISO 12,800 (Click to view full size)

Sony Alpha A55: Resolution test

As part of our review process we've implemented a new testing procedure. To test the Sony Alpha A55 image quality, we shot our resolution chart, each with the Sony 18-55mm f/3.5-5.6 DT SAM kit lens.

If you view our crops of the resolution chart's central section at 100% (or Actual Pixels) you will see that, for example, at ISO 100 the Sony Alpha A55 is capable of resolving up to 26 (line widths per picture height x100) in its highest quality JPEG files. Examining images of the chart taken at each sensitivity setting reveals the following resolution scores in line widths per picture height x100:

Resolution chart

Sony A55 Review: 0.4secs at f/8, ISO 100

JPEGs

ISO 100

Sony A55 Review: ISO 100 – 26 (Click to view full size)

ISO 200

Sony A55 Review: ISO 200 – 26 (Click to view full size)

ISO 400

Sony A55 Review: ISO 400 – 26 (Click to view full size)

ISO 800

Sony A55 Review: ISO 800 – 24 (Click to view full size)

ISO 1600

Sony A55 Review: ISO 1600 – 22 (Click to view full size)

ISO 3200

Sony A55 Review: ISO 3200 – 20 (Click to view full size)

ISO 6400

Sony A55 Review: ISO 6400 – 18 (Click to view full size)

ISO 12800

Sony A55 Review: ISO 12,800 – 18 (Click to view full size)

Raw files

ISO 100 raw

Sony A55 Review: ISO 100 – 26 (Click to view full size)

ISO 200 raw

Sony A55 Review: ISO 200 – 26 (Click to view full size)

ISO 400 raw

Sony A55 Review: ISO 400 – 26 (Click to view full size)

ISO 800 raw

Sony A55 Review: ISO 800 – 24 (Click to view full size)

ISO 1600 raw

Sony A55 Review: ISO 1600 – 24 (Click to view full size)

ISO 3200 raw

Sony A55 Review: ISO 3200 – 22 (Click to view full size)

ISO 6400 raw

Sony A55 Review: ISO 6400 – 20 (Click to view full size)

ISO 12800 raw

Sony A55 Review: ISO 12,800 – 20 (Click to view full size)

Sony Alpha A55: Sample photos

test image 1

Sony A55 Review: 1/80sec at f/2.8, ISO 250 (Click to view full size)

test image 2

Sony A55 Review: 1/80sec at f/2.2, ISO 200 (Click to view full size)

test image 3

Sony A55 Review: 1/80sec at f/2.2, ISO 100 (Click to view full size)

test image 4

Sony A55 Review: 1/320sec at f/2.0, ISO 100 (Click to view full size)

Sony Alpha A55 Review: Verdict

It would be very easy to dismiss this novel design as a gimmick, but for certain photographers it will provide a real advantage. Image quality is similar to contemporary conventional SLR cameras, but the size and weight of the A55 is much reduced, making this camera ideal for those who travel extensively, or just wish their SLR was a bit smaller and lighter.

Those who use live-view for general picture taking will appreciate the fast autofocus and articulated swivel screen. The phase detection AF that performs just as well when using the screen on the rear to compose images, as when using the viewfinder. In this respect the system is an improvement over Sony's Alpha SLRs with live view, and it already has the quickest live-view AF system.

The Sony A55 isn't a camera for everyone, though. Those looking for similar continuous shooting performance to the current crop of fast frame rate SLRs will be disappointed by the viewfinder blackout after shooting and the relatively small buffer. Fast memory cards are a must if this feature is to be an advantage, but even then those issues still remain.

Given the current Sony A55 price, it may still prove to be a compelling choice if the features meet your buying criteria, due to its decent image quality at high sensitivities, compact dimensions and support for existing Sony A-mount lenses.

Features: 4

Build quality: 3
Image Quality: 4
Value: 3
Overall: 4

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