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|John Riley reviews the Sony Alpha A55.|
The second of Sony's new SLT cameras that utilise the Translucent Mirror technology, or a pellicle mirror if you prefer, that transmits 70% of the light to the sensor and 30% to the electronic viewfinder. This new type of camera is effectively a hybrid with interchangeable lenses, plus of course having the advantage of an APS-C sized sensor and a slightly reduced bulk. The alternative way of viewing its place is a DSLR with no flipping mirror. Either way, the electronic viewfinder is the crux of the matter and the question is will the DSLR purchaser accept this new style of viewing?
Sony Alpha A55: Features
The Sony Alpha A55 is a digital, interchangeable lens camera with an APS-C CMOS sensor with 16.2M effective pixels. It features the Steady Shot system which moves the sensor to compensate for camera shake, giving an advantage of several stops extra hand-holding ability. Sony suggest 2.5 – 4 stops advantage, depending upon lens and circumstances. The anti-dust mechanism incorporates special coatings on the low pass filter and the sensor shift to remove unwanted detritus.
The AF system has 15 points, three of which are cross type sensors. There is AF illumination available when required.
The major difference between this camera and the DSLR is the translucent mirror. This should reduce vibration and makes possible a maximum frame rate of a blistering 10fps. Live View is no longer a special feature, but is available as standard, giving a 100% view on the generously sized 3 inch articulated rear screen.
A standard optical viewfinder would be very dull so the 30% reflected light is directed through an electronic viewfinder of 1.44M dots. This is as good as currently these viewfinders get, so we shall see whether or not it is good enough to be a viable replacement for the optical alternative.
Exposure control is via the “Exmoor” CMOS sensor and utilises a 1200-zone evaluative pattern. ISO settings between 100 and 12800 may be set, or an Auto option may be selected.
The shutter operates from 30 seconds to 1/4000 second, with flash synch at a relatively slow 1/160 second.
HD movies can be shot for up to 11 minutes with Steady Shot switched on and 29 minutes without. Autofocus is still active in movie mode.
A new feature in this model is the built in GPS, enabling the location of an image to be recorded via satellite triangulation. At its best, this can place the location an image was shot to within 98m, certainly accurate enough for most purposes.
Sony Alpha A55: Handling
The A55 feels well-proportioned and fits the hands well. All the controls are accessible and placed logically. There is no tendency to accidentally press any buttons.
Build quality is excellent, but the camera does feel quite light and less substantial than some. It is quite plastic in construction and although this may not detract from its performance it does reduce the feeling of confidence that it will stand up to more severe use.
In terms of practical use, I find that in general I use the rear screen for composition, especially if the camera is mounted on a tripod. This is convenient and it is an excellent screen, even in full daylight. The electronic viewfinder is probably the best I have seen so far, but it does tend to show quite a bit of colour fringing which I find uncomfortable. There are, however, many circumstances when eye-level viewing is needed and it performs well enough to substitute for an optical finder.
The EVF is good enough now, but I expect that future models will improve on this. On the other hand, the electronic level indicator is superb and having that in the eye level option is a definite advantage.
Sony Alpha A55: Performance
The first thing to note is that the A55 does seem to produce rather light images. There is no real detail lost in the highlights, so the mid-tones must be being shifted to the right of the histogram. Dialling in some exposure compensation corrects this to personal taste, so it is something to bear in mind. Likewise, dark and light subjects definitely need compensation to be correctly reproduced. This is true whether or not evaluative, centre-weighted or spot metering is used. I have a preference here for the centre-weighted option, which I find more predictable.
In one way it is surprising to find that spot metering gives probably the lightest result of all. However, another consequence of this is that bright highlights and areas of sky have very little if any detrimental effect on the exposure.
Focusing is impeccable. It locks on fast and is accurate. AF has now reached a very high level of performance and the camera here does a much better job than my eyes can. I feel there will be very few occasions when manual focus will need to be selected.
Resolution and noise are tied together and, firstly in terms of noise, the 16.2MP sensor performs very well indeed at moderate ISO settings. Up to ISO400 the highest quality is maintained. ISO800 sees the first degradation, but this is still well controlled. ISO1600 is still commendable, with tight noise pattern and good detail. ISO3200 is losing detail and beyond that the image is quite mushy and full of artefacts. By the time we reach ISO12800 images are full of speckled colour noise and the detail is highly compromised. It is still a good idea to provide these speeds though, as sometimes recording some image is better than not being able to record anything. It is always better to have a sharp, noisy image rather than a noise free one that is ruined by camera shake.
|Sony Alpha A55 Test chart ISO speed test: Click on the thumbnails for larger images.|
|Sony Alpha A55 Outdoor ISO speed test: Click on the thumbnails for larger images.|
The Steady Shot system works very well and does give at least a 3 stop advantage. This will depend upon the lens and the individual photographer, but it is a real advantage. The only exception is that there is no effect on subject movement, so for anything fast moving high shutter speeds will still be necessary.
Resolution at 16.2MP is very satisfactory and A3 prints will be well within the capability of the A55. Detail is very good at the lower ISO settings, providing sharp clean images of even the most intricate subjects.
Colour reproduction is subjective to some degree but the camera performs well in most circumstances. It is possible that the boldest colours are rendered slightly garishly, but more subtle hues are beautifully reproduced. Subtle clearly suits the Sony Alpha A55.
In general, the camera is fairly neutral, with a tendency towards being slightly cool. This is evidenced also in the behaviour of the white balance presets. AWB tends towards cold colours and to preserve some warmth the other presets do offer advantages. Daylight setting preserves the natural colour very well, or one of the other presets when appropriate. This is an area where the photographer can gain some definite benefit from experimenting with the various options.
White balance presets perform well in both artificial and daylight situations. It is only where clearly we are outside the norm, such as using AWB in incandescent lighting, that we exceed the ability of the system. When using flash it is also worth experimenting, just to see if the flash setting is actually the one that gives the result that is preferred.
Fill-in flash works very nicely using the inbuilt unit. Results are well balanced and with no tendency to blow out highlights, even when used quite closely.
The dynamic range of the camera is obviously extremely wide as detail is well retained in the highlights, even given the light exposures given, as noted above. I would still reduce exposure slightly from that indicated, but for matters of taste in the gradation of the image.
The battery provided is an infoLithium NP-FW50 rated at 1020 mAh. This seems to be quite a small battery for such a power hungry camera. After all, we have to switch on even to glance through the viewfinder, so the camera is constantly being switched on and off and either Live View or the EVF are in continuous use. The instruction book tells us that the battery will run out quickly in some circumstances, basically normal use.
My estimate is that with virtually no flash use a charge may be expected to last for some 250 shots, approximately. This is of course used over a day and with my style of use. Yours may be different, but in any event a couple of spare battery packs would seem to be a good idea.
The camera is highly responsive and is ready for use virtually instantaneously after being switched on. Normal use does not cause any particular delay, with the exception of very long exposures where the noise reduction systems perform dark frame subtraction. A delay equal to the exposure time ensues. High ISO noise reduction also has a similar effect.
In my test it took 38 frames at high speed for the buffer to fill and the camera to slow to a standstill. At that point a delay ensues whilst the buffer is cleared. Considering that we are talking here about the highest quality JPEG files, this is an excellent performance.
The GPS module is an interesting inclusion and this could be invaluable in a number of circumstances. In a way it's a pity that in the UK this cannot be converted into an Ordnance Survey grid reference, as this has a more immediate relevance to most users. Probably very few of us can readily equate our location to latitude and longitude.
Vibration is also an interesting feature of this camera design, or rather the lack of it. This should reduce the amount of shake in any image, but especially in the “hot spot” of shutter speeds that many DSLRs exhibit, where the effect of mirror slap is at its maximum. No mirror equals no vibration, only the minimal inertia of the focal plane shutter. There are definitely potential benefits of these new mirror-free designs.
The Sony DT 18-55mm f/3.5-5.6 SAM lens is typical of the modern, compact kit zoom lens. It is very light, being constructed mainly of plastics, even the mount, but it is well put together and clicks slickly into place on the camera body.
The pattern of performance is also well known – the lens is actually a very good performer and an excellent general purpose or introductory choice. Images are best when stopped down to f/8-f/16, but very acceptable at all apertures. The softer images wide open are most suitable for portraiture as models do not always appreciate lenses that are too sharp.
Performance is fairly even across the zoom range, clearly better at the centre of the field as we might expect. Detail close up is still good, and commendably so even wide open. Best aperture when close is around f/11-f/16.
Chromatic aberration is well controlled at the centre of the field, but under high magnification, quite obvious in branches against sky at the edges.
In terms of distortion, 18mm sees distinct barrelling, so architectural subjects need to be handled with care. By 35mm the distortion has almost cancelled out, but soon asserts itself again as pincushion. This becomes stronger as we zoom towards 55mm and is quite obvious.
Flare is very well controlled, but even so I feel it would be a good idea at this price level to include a lens hood. As well as reducing flare this can help to protect the lens and front element from knocks. I would suggest buying either the Sony bayonet lens hood or a suitable alternative.
In summary, I would be happy to use this standard kit zoom. It is well made, performs well and is a useful introduction to the range of Sony and Carl Zeiss optics.
|DxOMark provides objective, independent, RAW-based image quality performance data for lenses and digital cameras to help you select the best equipment to meet your photographic needs.
Visit the DxOMark website for tests performed on the Sony Alpha A55.
Sony Alpha A55: Verdict
There is no doubt that this is an enjoyable and versatile photographic tool, capable of very fine results. Access to the range of Sony/Carl Zeiss lenses has to be a major plus point, and at a reasonable cost too. The lack of mirror slap reduces potential vibration and also enables very high frame rates.
Competition therefore comes from other mirrorless interchangeable lens cameras and from conventional DSLRs. Professionals needing rugged workhorse cameras may well stick with the DSLR. Those wanting something more compact will be looking to dispose of the mirror system.
Bearing in mind that none of the mirrorless cameras are truly pocketable and that therefore we need to carry a camera bag, albeit a reduced size, this Sony probably ends up being the best of both worlds rather than the master of neither. There is a slight question mark over whether or not users will take to the new EVFs, but it could be a very good choice for those tempted by other mirrorless systems that have far less selection of lenses. Others may be more comfortable with the entry level conventional DSLR, but the battle has definitely been engaged.
In that middle battle ground the Sony Alpha A55 performs well and is good value for money.
Sony Alpha A55: Pros
High resolution images
Access to high quality lens range
High Frame Rate
AF in Movie Mode
GPS Module built in
Sony Alpha A55: Cons
Metering gives very light images
Loss of quality at high ISO values
Resistance to concept of EVF
|VALUE FOR MONEY|
Sony Alpha A55: Specification
|Sensor size||23.5 x 15.6mm|
|Max. Image size||4912 x 3264|
|Viewfinder||Electronic 100% coverage|
15 points (3 points cross type)
|Focus types||Continuous, Single Shot, Automatic, Manual Focus|
|File types||JPEG, DPOF, RAW, RAW & JPEG, AVCHD, MP4|
|ISO sensitivity||ISO100 - 12800|
|Metering system||TTL phase detection system|
|Metering types||Multi segment, Centre weighted|
|White-balance||Daylight, Shade, Cloudy, Incandescent, Fluorescent, Flash|
|Exposure compensation||+/-2.0 EV, 1/3 EV step|
|Shutter speed range||30 - 1/4000 sec.|
|Continuous shooting||Up to 7fps|
|Movie mode||AVCHD (1920 x 1080) / MP4 (1440 x 1080)|
|Monitor||3in Xtra Fine TruBlack LCD|
|Media type||Memory Stick PRO Duo/PRO-HG Duo, SD/SDHC/SDXC Memory Card|
|Interface||USB 2.0 Hi-Speed, HDMI mini connective, BRAVIA Sync, PhotoTV HD|
|Power||NP-FW50 rechargeable battery
|Size (wxdxl)||124.4 x 92.0 x 84.7mm|
|Weight (with battery)||441g|
The Sony Alpha A55 costs £599 and is available from Warehouse Express here:
Sony Alpha A55