Sony DT 18-55mm f/3.5-5.6 SAM

Replacing Sony's 18-70mm as the standard kit lens bundled with their digital SLRs, the 18-55mm was released as a better quality replacement that is also more compact and lightweight. If you were to buy one on its own, as a replacement or an upgrade, it would set you back just under £130.For a few extra pennies - actually 600 extra pennies as it costs £190 - will get you Sigma's 18-50mm f/2.8-4.5 DC OS, which has optical stabilisation you can see through the viewfinder and a brighter maximum aperture.

Sony DT 18-55mm f/3.5-5.6 SAM: Handling and features
Sony's 18-55mm is typical of similar lenses in terms of size and weight. The lens barrel is constructed from lightweight plastics, but the finish is good. A silver band around the front of the zoom ring finishes off the look rather nicely.

In terms of features, this lens is fairly basic. Focusing is performed by rotating the front element, which may pose problems when using polarisers or ND grad filters. The lens accepts 55mm filters, which are fairly common and cheap to purchase. Sony's Smooth Autofocus Motor powers the focus action. The motor isn't silent like Sony's SSM models, but AF is pretty responsive all the same.

Sony DT 18-55mm f/3.5-5.6 SAM: Performance
It was quite a pleasant surprise when I started to get the results through for this lens. For a kit lens it is really rather good - and much better than others I have tested.

At 18mm, sharpness in the centre is already excellent from f/3.5, and peak quality is achieved at f/4 where the centre is still excellent, but the edges are very good. Diffraction starts to reduce the resolution slightly after f/5.6 but the lens still performs well down to f/16 at this focal length.

It is a similar story when zoomed to 35mm, except the sharpness towards the edges of the frame suffers a little at maximum aperture. Peak quality is achieved at f/8 here where the centre is excellent and the resolution towards the edges is still very good.

Finally at 55mm, the overall performance of the lens drops a little, which is typical of this kind of lens, but it still produces images with good resolution at f/5.6 and f/8. At smaller apertures, diffraction takes a bite out of the sharpness.

Resolution at 18mm	Resolution at 35mm
Resolution at 55mm
	How to read our graphs The blue column represents readings from the centre of the picture frame at the various apertures and the green is from the edges. Averaging them out gives the red weighted column. The scale on the left side is an indication of actual image resolution. The taller the column, the better the performance. Simple. For this review, the lens was tested on a 12Mp Sony Alpha A500 using Imatest.

Chromatic Aberrations are very well controlled by this lens with the highest levels never exceeding half a pixel width. This should pose few issues under normal picture taking conditions.

Chromatic Aberrations at 18mm	Chromatic Aberrations at 35mm
Chromatic Aberrations at 55mm
	How to read out charts Chromatic aberration is the lens' inabiity to focus on the sensor or film all colours of visible light at the same point. Severe chromatic aberration gives a noticeable fringing or a halo effect around sharp edges within the picture. It can be cured in software. Apochromatic lenses have special lens elements (aspheric, low dispersion etc)  to minimise the problem, hence they usually cost more.

Fall-off in image illumination towards the corners is reasonably well controlled. At 18mm and f/3.5 the corners are 1.53 stops darker than the image centre. Stopping down to f/5.6 achieves uniform illumination. The amount of fall-off at 55mm is even less apparent. Imatest recorded that the corners are only 0.64 stops darker than the image centre at f/5.6. Stopping down to f/8 will provide even illumination.

Lenses of this type typically suffer from noticeable barrel distortion at 18mm and his lens is no exception. Imatest recorded barrel of 4.48% which may pose problems if straight lines are important. At 55mm the barrel distortion diminishes. Here Imatest recorded only 1.6% barrel. At both ends of the zoom the distortion pattern is uniform, so it should be easy to straighten things up afterwards in editing software.

Click on the thumbnails for a high resolution image
The resolution in the centre is very good. Every last detail of this donkey has been rendered sharp.	No CA is visible, even on this high contrast building.

Strong point sources of light within the frame may cause quite prominent flare patterns and loss of contrast if the light is strong enough. No hood is supplied with the lens, and as the front filter ring rotates, it is impossible to use a highly efficient petal-shaped hood. The lens is as prone to flare from bright light sources outside of the frame as it is from those within the frame.

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 DT 18-55mm f/3.5-5.6 SAM.

Sony DT 18-55mm f/3.5-5.6 SAM: Verdict
Kit lenses are usually nothing special, but this lens has proved itself a very capable performer during testing, especially in the areas of resolution and control of colour aberrations.

Although the features of this lens are basic, if you can live without the luxuries of internal focusing, a wider maximum aperture, or a silent focus motor, then this lens could well meet your needs, especially in terms of image quality.

Sony DT 18-55mm f/3.5-5.6 SAM: Pros
Good resolution performance
Good control of CA
Compact and lightweight

Sony DT 18-55mm f/3.5-5.6 SAM: Cons
Rotating front element
Barrel distortion at 18mm
Can be prone to flare

FEATURES
HANDLING
PERFORMANCE
VALUE
OVERALL

Sony DT 18-55mm f/3.5-5.6 SAM: Lens specification

Price	£130
Contact	www.sony.co.uk
Filter size	55mm
Format	APS-C
Construction	8 elements in 7 groups
Angle-of-view	76-29 degrees
35mm equivalent focal length (on APS-C body)	27-82.5mm
Internal focusing	No
Image stabilisation	No
Minimum focus	25cm
Maximum aperture	f/3.5-5.6
Minimum aperture	f/22-36
Weight	210g
Size	69x69.5mm

The Sony DT 18-55mm F/3.5-5.6 SAM costs around £130 and is available from Warehouse Express here:

Sony DT 18-55mm f/3.5-5.6 SAM

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