Tamron SP AF 17-50mm F2.8 XR Di II LD (IF)

BACKGROUND
I had been looking to replace the so-so kit lens on my Canon 400d and agonised over the possible options for several weeks. I wanted a lens to broadly replace the kit lens range of 18-55mm - with a good wide angle and some telephoto zoom, but not too much of a range so that optical quality would be compromised. Oh, and not too expensive please!

The Tamron 17-50mm f2.8 soon became a front runner from the scraps of user comments I found on the web. Hopefully my review below can fill in the gaps for other potential purchasers.

TECHNICAL DETAILS
Range 17-50mm (on 400d: 27-80mm)
Aperture f2.8 to f32
Physical Length at 17mm - 9cm
Physical Length at 50mm - 12cm
No USM or Image Stabilisation
No macro mode
Zoom lock switch prevents barrel movement when stored
Filter diameter 67mm
Included items - Lens caps and hood
Warranty - one year

DECODING THE NAME
You could accuse Tamron of just trying to cram in every letter of the alphabet and they have done a good job, but it does mean something. The 2.8 obviously refers to the maximum f2.8 aperture, constant throughout the whole focal range. XR, LD and ASP (aspherical) refer to the glass elements having characteristics to reduce aberration and distortions. To the normal user this boils down to good optical quality in an unusually compact design.

FEATURES AND OPERATION
The first thing you notice if you are only used to the kit lens is that the Tamron is appreciably heavier and this will be apparent after a whole day with the camera around your neck. With lenses though, weight usually equals quality glass and good build quality and the Tamron is no exception. The rubberised focus and zoom rings are smooth in operation but it's worth pointing out that the zoom rotates in the opposite direction to Canon lenses. There is a distance scale marked on the focus ring.

Although the focus motor is noisier than the kit lens, it is no more so than the popular Canon 50mm 1.8 (or "nifty fifty") and shouldn't be an issue for most users. The only time you will really notice it is when changing focus over a long range - then you will hear it's distinctive “whizzing”. Despite the sound effects, focussing is quick and accurate and even in low light against relatively plain backgrounds there is very little 'hunting'.

This lens does not have a close-up macro capability as such, but it can accurately focus at 9cm from an object at full telephoto (50mm) increasing to about 12cm at wide (17mm). This is considerably less than the 27cm that Tamron advertises. (I measured from the front of the lens to the object).

The constant aperture of f2.8 is of particular use in low light conditions but you will also need to increase the ISO to make most use of it due to the lack of any stabilisation function. The rather dim viewfinder image that you got with the kit lens is also brightened up owing to this wider aperture. With 7 aperture blades, background blur (or "bokeh") on wide aperture shots is pleasantly soft.

IMAGE QUALITY
No problems with build or operation, but what do the pictures come out like? The amazing sharpness is what strikes you first, even when viewed on the camera's LCD screen. Pictures are razor sharp, especially with an aperture around f8. For the first time with a digital camera, I can crop sections and display at 100% of their size on screen and still be amazed at the sharpness. In fact on some occasions I have had to REDUCE the level of sharpening applied during raw processing.

This sharpness is pretty even across the whole of the image though there is slight degradation in the extreme corners at the wider end. Away from the very widest focal lengths though the edge to edge sharpness and lack of distortions can give the 50mm a run for it's money, so much so that I don't think I really need to bother with it (I don't need to go down to a 1.8 aperture - the only reason left for getting it).

On the downside, there is some noticeable chromatic aberration at the widest focal length, which exhibits itself as purple fringes around contrasting objects (eg a white window frame against a dark wall). This can be easily corrected in software, as can the barrel distortion that is common to many wide angle lenses. This distortion however is not severe and quickly disappears as the focal length increases.

ACCESSORIES
Supplied as standard is a hood useful for shooting in sunny conditions. The hood can be reversed and sit over the lens body when not required, this only partly obscures the zoom ring although the focus ring is not accessible. A nice touch is that the front lens cap has a release in the centre as well as the edge - making it easier to remove and replace the lens cap with the hood fitted.

OTHER CONTENDERS
Sigma 17-70 f2.8-4.5 macro (Around £240)
Around the same price and offers a macro capability in addition to the longer zoom. However the f2.8 aperture only applies at the 17mm wide end, it soon rises to f4 at 50mm and f4.5 at 70mm. Internet forums also appear to contain many comments from people with quality control and focus issues with their Sigma lenses.

Sigma 18-50 f2.8 Macro (Around £300)
I have no information on this one.

Canon 17-85 f4.5-5.6 with IS & USM (Around £340 including Canon £100 rebate)
More expensive but with Image Stabilisation and an Ultrasonic motor for quiet focussing. The longer zoom would be useful, but overall I wasn't too impressed with image samples or reviews that I saw.

OVERALL
It is difficult to fault the Tamron (or "Tammy" to it's friends). It packs good quality glass into a compact design, can produce wonderfully sharp pictures and carries pretty much a bargain price tag. Apart from some chromatic aberration and barrel distortion at the widest setting there isn't really anything to complain about.

I touched on Sigma quality control issues above, and Tamron has suffered some negative comments in this department, although not specifically related to this lens. The general consensus seems to be that the chances of getting a duff copy of a Tamron lens is lower than that of a Sigma, but higher than a Canon. This isn't to say however, that sticking with Canon will guarantee you a perfect lens every time.

I would always recommend to buy your lenses from a bricks-and-mortar shop, rather than online. That way you can fully examine their suitability, as well as ensuring you get one that operates as it should. It needn't be that much more expensive if you are prepared to travel.

As a kit lens replacement, I don't think you could reasonably find a better lens, especially at this price level, indeed more expensive lenses would be hard pushed to match it's image sharpness.

FINAL THOUGHT
It may not have a red ring around the front, but it does have a nice gold one!