Sony DT 16-50 mm f/2.8 SSM
3. Build quality
As you can see the Sony, when it comes to dimensions and weight, can be placed in the middle of the whole group. It is worth mentioning, though, that, next to the Tamron, it is optically one of the most complicated devices. When it comes to the number of diaphragm blades it lags behind the whole group with the Tamron as well – it has just seven of them whereas its competitors have nine.
In the photo below the Sony DT 16-50 mm f/2.8 SMM is positioned next to the Sony 50 mm f/1.4 and the Sigma 30 mm f/1.4 EX DC (the Sony mount version lacks an HSM motor).
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The lens starts with a metal bayonet mount with contacts which surrounds a rear element with a diameter of 24 mm. The element is positioned almost on the same level as the mount at 16 mm and it hides about 3 centimeters inside when we pass to 50 mm. At that point you can glance inside the lens. It is darkened well but unfortunately you can glimpse electronic parts as well.
The proper tube starts with a narrow ring on which you can find an orange dot which makes attaching the lens to a body easier, and a plate with a name and a serial number. There is also an inscription that the lens was made in China.
A zoom ring is the next, noticeably wider element of the tube. It is 27 mm wide and most of it is occupied by rubber ribbing. In the part situated closer to the mount we can find focal lengths markings at 16,24,35 and 50 mm and a LOCK switch which makes it possible to lock the lens in the folded position. I didn’t use it one single time, though, because the tube doesn’t have a tendency to extend under its own weight. The ring itself works correctly although you can feel a slightly bigger resistance in the middle of the focal range and the ring is a bit loose at both ends.
Further on you see a distance scale, expressed in feet and meters, behind a window. Below there are parameters of the lens and on the left there is a focusing mode switch (AF/MF); you can also find the SONY inscription on the right.
A manual focus ring, covered by rubber ribs, is the next element. It is 12 mm wide and it works smoothly both in MF and AF mode. Running through the whole distance scale takes a turn through 90 degrees.
Further on you can find a front element set which extends on a solid but plastic tube. The ring which surrounds the front element, on which you can see the name of the lens and its filter diameter, is made of metal, though. A hood mount and a non-rotating filter thread, 72 mm in diameter stick out from it. The front element has a diameter of as much as 62 mm. On passing from 16 to 50 mm the lens increases its length by almost three centimeters.
When it comes to the inner construction we deal here with as many as 16 elements positioned in 13 groups. The producer didn’t spare special elements – there are two aspherical ones and three made of low-dispersion ED glass. Inside the lens there is also an aperture with seven diaphragm blades which can be closed down to f/22.
In a set with the Sony SLT A77 camera which you can find in retail shops, apart from the lens itself there are also two caps and a lens hood.