Lens review

Sigma 30 mm f/2.8 EX DN

29 March 2012
Arkadiusz Olech

3. Build quality

When it comes to lenses with a focal length near 30 mm for mirrorless cameras featuring an APS-C/DX sensor, apart from the Sigma, tested here, we’ve got two or three other possibilities. If you extend the focal length to 40 mm there will be actually three of them. The appropriate comparison is presented in the following chart. The Sony is optically the most complex and the biggest in this group but, as a Macro construction, it is a law unto itself. The Pentax is an extreme system for a change – its constructors had clearly the minimization of dimensions in mind. It would be difficult to compare it to the Sigma. It seems the Samsung remains the most similar and the easiest to compare – its focal length and the angle of view are the same but, while a bit faster, the Samsung is smaller and physically lighter than the Sigma. Its optical construction is surprisingly simple and efficient at the same time – it got very good results in our tests. The Sigma, slower, being bigger and more optically complex, should defeat the Samsung in all optical categories then. Whether or not it is true you can find out in the next chapters.

In the photo below the tested Sigma 2.8/30 is positioned next to the Samsung NX 2/30 and the Sigma 1.4/30. All of these instruments are designed for an APS-C sensor.

Sigma 30 mm f/2.8 EX DN  - Build quality

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The Sigma starts with a metal mount with contacts. The mount surrounds a rear element, about 2 cm in diameter, and is hidden ca. 1 cm deep inside the casing.

Sigma 30 mm f/2.8 EX DN  - Build quality

The casing itself is very ascetic. First you see a narrow, immobile and ribbed ring behind which there is a smooth part with the name of the lens, its serial number and the focusing mechanism range. The next part is a manual focus ring. It is almost 18 mm wide and is covered by rubber ribs. It works with new linear AF motor without the need of gears – after detaching the lens from the body the movements of the ring don’t make elements change their position. When attached to a camera and set in the manual focus mode the ring is well-damped and allows you precise settings. Running through the whole distance scale takes a turn through about 140 degrees.

The focus ring is the final element of the lens. In the front there is also a non-rotating filter thread, 46 mm in diameter, which is surrounded by an inscription with the name of the lens and the information that it was produced in Japan. The front element is immobile and small – its diameter amounts to just 7 mm.

It is a pity the Sigma constructors didn’t include some space for a distance scale and a depth of field scale on the casing. A fixed-focal lens of this class could really do with both of them.

When it comes to the inner construction we deal here with 7 elements positioned in 5 groups. Two elements are aspherical. Inside there is also an aperture with seven diaphragm blades which can be closed down to the value of f/22.

Sigma 30 mm f/2.8 EX DN  - Build quality

Buyers get both caps and a stylish case in the accessory kit.

Sigma 30 mm f/2.8 EX DN  - Build quality