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Lens review

Tamron SP 24-70 mm f/2.8 Di VC USD

23 June 2012
Szymon Starczewski

3. Build quality and image stabilization

Traditionally let’s start with comparing the tested lens to its direct rivals with the same or very similar parameters. The following chart will make it easier. It is evident that the Sigma is physically the lightest and the smallest lens of them all but it must be emphasized that the Tamron is very close behind. The Sigma had it easier to keep the dimensions and weight in check because it doesn’t feature any stabilization so there are just 14 elements in its optical construction. The number of Tamron’s elements is higher – small wonder it is also a bit heavier. What’s interesting, the Canon, the Nikkor and the Zeiss, although heavier than the tested lens, don’t have any optical stabilization, the Canon being optically the most complex instrument of them all. Three lenses, namely the Canon, the Sigma and the Tamron, make it necessary to use filters of a huge diameter - that of 82 mm. All devices feature an ultrasonic autofocus motor. The Zeiss sticks out because of the shortest minimum focus distance. The photo below shows the tested Tamron positioned next to the Nikkor of the same parameters and the Sigma 30 mm f/1.4 EX DC HSM

Tamron SP 24-70 mm f/2.8 Di VC USD - Build quality and image stabilization

The Tamron SP 24–70 mm f/2.8 Di VC USD starts with a metal mount which surrounds a plastic insert; inside it you can find contacts and a rear element, 30 mm in diameter. The rear element changes its position with the change of focal length; it is on the same level as the mount at the minimum focal length and it hides about 2.5 centimeters inside the casing at the maximum focal length. The movement exposes the interior of the lens so you can see a lot of shiny electronic parts. It means the device is rather not completely air-tight or perfectly darkened.

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Tamron SP 24-70 mm f/2.8 Di VC USD - Build quality and image stabilization


Moving to the proper body of the lens you can notice that its outer casing is made of plastics. Immediately behind the mount, on the left, there are two switches. The first of them is used to select the focusing mode (AF/MF) and the second one switches the stabilization on and off (VC Off/On).

Tamron SP 24-70 mm f/2.8 Di VC USD - Build quality and image stabilization

Looking at the lens from above the first thing you see are two inscriptions: „Ultrasonic Silent Drive” and „VC”, meaning that this lens was equipped with an ultrasonic autofocus motor and optical stabilization. Over the inscriptions you can also find a distance scale behind a window, expressed in feet and meters. The next part is a rubberized, ribbed manual focus ring. It works in the MF and the AF mode but it is quite narrow - just 1 cm wide – so practically the narrowest ring in all modern 24-70 mm class lenses. Still it moves smoothly and is well-damped so its work quality is beyond reproach. Running through the full distance scale needs a turn through about 110 degrees.

The next element of the casing features a gold stripe with the name and the parameters of the lens. A rubberized, ribbed zoom ring, 4 centimeters wide, can be found immediately behind. It includes focal lengths markings at 24, 35, 50 and 70 mm and an inscription „Made in Japan”. The ring works smoothly and well-damped in the whole range. When passing to 70 mm focal range a homogeneous tube with the front element system is pulled out so the lens becomes longer by a bit over 3 centimeters.

The device ends with a hood mount which surrounds a non-rotating filter thread, 82 mm in diameter. The front element is relatively flat, with a diameter of 7 cm.

When it comes to the optical construction we deal here with 17 elements set in 12 groups. It is evident the producer didn’t save on special elements. We have here three elements made of low dispersion LD glass, three aspherical and one hybrid-aspherical element plus two elements made of glass with a high refractive index (XR). Inside you can also find a circular aperture with nine blades which can be closed down to f/22.

Tamron SP 24-70 mm f/2.8 Di VC USD - Build quality and image stabilization

Buyers get two caps and a petal type lens hood in the box. It is a pity that the producer didn’t add a case which, when it comes to the rivals in this class of equipment, is often a standard issue. It is worth reminding though that buying a Tamron you get a significant warranty period, as long as five years.

Tamron SP 24-70 mm f/2.8 Di VC USD - Build quality and image stabilization

Stabilization

Tamron started to equip its lenses with an optical stabilization system not so long ago. In the case of the 24-70 model the system was implemented in the lens itself - that feature sets the tested device apart from other, not stabilized rivals.

The efficiency test was conducted at 70 mm using the Canon EOS 50D body. For every exposure time, ranging from 1/125 to 0.5 of a second, we made several dozen photos with the stabilization switched on and off. The results of our experiment can be seen on a graph below – it presents a percentage of blurred photos depending on the exposure time, expressed in EV. The value of 0 EV is an equivalent of 1.80 of a second.

Tamron SP 24-70 mm f/2.8 Di VC USD - Build quality and image stabilization

A maximum distance between two obtained curves is recognized by us as the measure of the stabilization efficiency. In this case it reaches 3 EV which is a very good result, gaining our recognition.