The following chart presents a comparison between basic properties of the tested lens, its two predecessors and rivals with a range of 18-300 mm. What’s interesting, the Tamron 18-400 mm is hardly the most optically complex instrument in this group. Still physically it remains the heaviest and the longest for sure.
In the following photo the tested lens is positioned next to the Sigma EX 17–50 mm f/2.8 OS HSM and the Canon EF 35 mm f/2 IS USM.
The tested lens starts with a metal mount which surrounds contacts and a rear element, 21 mm in diameter. That element is situated on the same level as the contacts with the focal length set at 18 mm. After changing the focal length to 400 mm it hides inside about 6 cm deep. The interior of the tube is nicely matted and blackened – it would be difficult to have any reservations here.
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A rubber gasket joined with a metal, immobile, silver ring is the first part of the proper body of the lens. That ring turns into smooth, black casing with a white mark making an alignment with a camera easier. Above that mark you see a focusing mode switch (AF/MF) and a stabilization unit switch (VC ON/OFF). Right next to them there is a big inscription “DESIGNED IN JAPAN” and then “MADE IN CHINA” in smaller print, along with the filter diameter which is 72 mm. Looking the other way round you see an inscription TAMRON and a LOCK switch on its right. That switch is used to block the tube of the lens at 18 mm. Fortunately we didn’t have to use it often; neither the pull of gravity nor sudden movements of the photographer could trigger any tendency to creep.
Then you see a zoom ring, 43 mm wide, with most of its surface covered by rubber ribs. Under the ribbing you see focal length marks at 18, 35, 50, 70, 100, 200, 300 and 400 mm, along with an inscription with the name and parameters of the lens. The ring doesn’t move evenly – the most pronounced resistance you feel in the middle of the focal range, the smallest on both edges.
Further on you see a ribbed manual focus ring, 14 mm wide. It comes without any distance or depth of field scale. It moves smoothly but with its tension we found a bit too small to make us satisfied. Running through the whole distance scale needs a turn through an angle of about 70 degrees. It is a very low value, making the entire process of manual focusing moot especially at the longest focal lengths.
The front element is 61 mm in diameter, surrounded by a non-rotating filter thread, 72 mm in diameter, and a hood mount. The whole front element system extends with the increase of the focal length so by 400 mm the lens is 9.5 cm longer. The tube is of telescopic kind and made entirely of plastics.
The optical construction of the Tamron 18-400 mm consists of 16 elements positioned in 11 groups. Among them you can find three LD low dispersion glass elements, two moulded aspherical ones, and one hybrid aspherical element. Inside there is also an aperture with seven blades which can be closed down to values ranging from f/22 to f/40, depending on the focal length. All of these are hidden in a stylish casing, clearly modelled after the newest SP and G2 series. The construction is supposed to have moisture resistance with several seals throughout the body.
The lens is also compatible with the Tamron TAP-in Console for connecting it to a PC. That way you can upgrade its software easily and adjust the AF and VC systems with great precision.
Buyers get in the box two caps and a petal-type hood.
Optical stabilization
The Tamron 18–400 mm f/3.5–6.3 Di II VC HLD is equipped with an optical stabilization unit and its producer claim 2.5 EV stops improvement (according to the CIPA standard). It is interesting because usually producers declare a four-stop efficiency. Of course we decided to check it. With the lens set at the maximum focal length, we took several dozen photos at every exposure time ranging from 1/640 to 1/10 of a second with the stabilization switched on and off and then we determined a percentage of blurred photos for each set. The appropriate graph showing that percentage, correlative with the exposure time expressed in EV (with 0 EV being an equivalent of 1/500 of a second), you can find below.
The maximum distance between both curves reaches a bit higher than 3 EV and such is, in our opinion, the efficiency of the optical stabilization unit of the tested lens. It is a result a tad higher than declared and very good at the same time, especially if you take into account the fact that this lens is aimed at amateur photographers.
