Sigma 150-500 mm f/5.0-6.3 APO DG OS HSM
3. Build quality and image stabilization
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From the side of the mount onwards we find a clear distance scale, conventionally in feet and meters, behind a glass window, next a collar for a tripod adapter, which is included in the set. Above, there is a notice with the name and the lens’s symbol and on the left, we see an auto/manual focus mode selector (AF/MF) and a stabilization mechanism mode switch (OFF,1 – for normal photos, and 2 – for photos of objects in motion).
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Next, we find a comfortable and precise manual focus ring, which can work in both MF and AF modes. Above there is a notice “OPTICAL STABILIZER” and on the left we’ll find a zoom lock switch. It is a very useful feature, as the front element moves in and out under its own weight.
In the next part of the tubus we see a wide focus ring, which moves smoothly but with due resistance. On zooming to 500 mm, the lens’s front element extends as much as almost 33 cm; it is surrounded by a filter thread which does not rotate on autofocusing, with a diameter of 86 mm so very huge. Such significant dimensions mean that the filters won’t come cheap. If you want to buy a, let’s say, Sigma UV filter, you will have to pay 460 PLN. If you need a polarized filter, there will be 800 PLN less in your wallet.
Because of the stabilization, there is significantly more optical elements inside the lens. We have as many as 21 elements in 15 groups. Three of them (two from three big front elements) are made of the low dispersion glass SLD. A circular aperture diaphragm with nine blades, which can be closed down, depending on the aperture, to f/22 or f/29 complements the picture.
It’s worth notice, that the lens, compared to its rivals or even to the Sigma 120-400 mm, is quite slow. The f/5.0 aperture remains only in the 150-165 mm range. From 165 mm to 290 we get f/5.6 and above 290 mm – only f/6.3 In the most interesting focal range, from 300 mm upwards, the lens is slower than the Sigma 120 – 400 mm or even than the 70-300 mm class zooms which, at 300 mm have the relative aperture value of f/5.6…
The Sigma 150-500 mm buyer gets a lens hood, a tripod adapter and a hard case in the set.
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Stabilization
The stabilization inside the Sigma 150-500 mm is supposed to work with the efficiency of 4 EV. A similar assurance was made in the case of the Sigma 120 –400 mm, tested not so long ago but the measurement results were more closer to the 2 EV level. When we look at the measurements made for the 150 –500 mm model at 300 mm focal length, presented in the picture below we see that the efficiency is indeed about 2 EV.
The zero point in the EV scale corresponds to the exposure time of 1/640 second. It can be noticed, that the curves, showing the dependence between the number of bad pictures and the expossure time, are about 2 EV apart.
