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As we mentioned in our introduction, lenses which focal range starts from 70-100 mm and end at 400 mm are offered by the majority of producers; that’s why preparing the following chart was a very easy task. As you see the Tamron is a device optically the simplest and it is one of the reasons why it is also physically the lightest. Still the difference between the weight of the Tamron and the Sigma is very slight. However, the tested lens is a tad faster aperture wise than the Sigma. Both the Sigma and the Tamron are slower than their brand name rivals at the longest focal length.

In the photo below the Tamron 100–400 mm is positioned next to the first version of the Canon with almost the same parameters so the Canon EF 100–400 mm f/4.5–5.6L IS USM.

The tested lens starts with a metal mount surrounding a contact plate and a nice, properly matted and ribbed tube. Inside the tube you see a movable lens, 23 mm in diameter. At 100 mm focal length it is situated about 1 cm inside; when you pass to the maximum focal length it hides over 5.5 cm, revealing the rest of the inner tube, as meticulously matted and blackened as the rest. Glancing inside you cannot spot any electronic parts.

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The first part of the proper body of the lens is a rubber gasket joined with a metal, silver ring which doesn’t move. That ring turns into a smooth, black casing with a white marker, making an attachment to a camera easier.

The next ring features a distance scale, expressed in meters and feet, which is protected by a pane. On its left (looking from above) you find a focusing mode switch (AF/MF/LIMIT) and a stabilization switch (VC OFF/MODE1/MODE2). Right next to them there is a big inscription “DESIGNED IN JAPAN”, and then, a bit further on, it is written “MADE IN CHINA” and the letters are smaller. Then you see an inscription with the filter diameter, that of 67 mm, and other parameters of the lens.

A manual focus ring is the next part of the lens. It is 28 mm wide and its surface is completely ribbed. It moves smoothly with a slight but still completely acceptable resistance. Running through the whole distance range takes a turn through an angle of 120 degrees.

Further on, you find a smooth part of the barrel on which there is a LOCK switch which blocks the whole mechanism at 100 mm. We record its presence but we have to add we didn’t have to use it at all during our test. The lens had absolutely no gravity zoom tendency, not even after several sudden movements. The top-notch mechanics of Tamron is obvious at that point.

A zoom ring, 59 mm wide, is the biggest part of the barrel. Most of its surface is covered by ribbing and below you see focal length markings at 100, 135, 200, 300, and 400 mm.

The front element is 60 mm in diameter and surrounded by a non-rotating filter thread, 67 mm in diameter, and a hood mount. After passing from 100 to 400 mm the whole front element system extends on a plastic tube and so the length of the lens can be increased by 73 mm.

When it comes to optical construction, you deal here with 17 elements positioned in 11 groups. Three of them are made of low dispersion LD glass. Inside, you can also find a round aperture with nine diaphragm blades which can be closed down to a value ranging from f/32 to f/45 at the maximum, depending on the focal length you employ.

Buyers get both caps and a hood in the box. The accessory kit is the same as that of the rival Sigma but a bit modest if you compare it to the accessories of the Canon 100-400 mm II and the Nikkor AF-S 80-400 mm VR. In the case of these two brand name lenses you also get tripod adapters and hard cases.

Optical stabilization

In order to check how efficient the optical stabilization mechanism is we set the lens at 400 mm and took several dozen photos with exposure times ranging from 1/400 to 1/5 of a second and the stabilization switched on and off. For every set of photos was determined a percentage of out-of-focus shots; then we presented it in a form of a graph of exposure time which was expressed in EV (with 0 EV being an equivalent of 1/320 of a second).

The maximum distance between both curves, measured by us, reaches about 3.5 EV and such is, in our opinion, the real efficiency of the new Tamron’s Vibration Compensation system. It is a good result. Still, we must say the Tamron fares a bit weaker than the Sigma and other brand name rivals in this category. The Sigma 100-400 mm could reach about 3.7-3.8 EV, the result of the Canon EF 100–400 mm f/4.5–5.6L IS II USM was on a level of 4 EV, and the Nikkor AF-S 80–400 mm f/4.5–5.6G ED VR could even get to 4.3–4.5 EV.