Review of the Sigma 18-50mm f/3.5-5.6 DC HSM lens
With an official price that sits under £100, this is a very affordable lens that steers clear of the flimsy feel normally associated with such a low price-point. Its size is best described as ‘comfortable’: it is neither so small as to be awkward to use nor so large that it becomes a milestone when carried all day.
The optical construction might be called old-fashioned since it uses a mere eight elements, each of which provides its own group. With so few glass-air surfaces it would be reasonable to expect good transmission and image clarity but, potentially, visible chromatic and spherical aberrations. In fact the lens turns-in a remarkably good performance and although there is chromatic aberration towards the edge of the frame, especially at short focal lengths and wide apertures, the results are very acceptable overall.
The foremost manual-focus ring is narrow but usable: although the zoom-ring is wider it is also positioned so much closer to the camera body that some users find themselves using its leading edge rather than the full width of the grip. This is made more significant by the fact that the focusing ring rotates in AF mode and carelessly-placed fingers might obstruct its movement.
Inevitably, on a lens as inexpensive as this one, there must be compromises. Partly these come in an unremarkable overall specification but mostly they are to be seen in the very modest maximum aperture, which ranges from f/3.5 at the 18mm setting to f/5.6 at the 50mm setting. Low-light use will be limited by these apertures but more important is the unavailability of narrow depths-of-field, which will limit creative picture making.
Within its own limitations, and especially with such a low recommended retail price, Sigma’s 18-50mm f/3.5-5.6 zoom is an impressive lens. It is probably not a long-term purchase but it would make an excellent initial choice.
The entry-level 18-50mm f/3.5-5.6 does look a little bare. It doesn't have a focused-distance window (and therefore no depth-of-field indication) but the entry-level Sigma doesn't even have any external distance markings. It is, however, exceptionally affordable and that is an important consideration these days!