Sony DT 50mm f/1.8 SAM review

At the risk of making the rest of this review redundant, it is worth saying at the outset that Sony's DT 50mm f/1.8 SAM is a fantastically affordable lens that produces some very impressive results indeed. Admittedly it has a fixed focal-length so falls short in terms of all-round flexibility but that doesn't stop it from being an absolute bargain.

There was a time when almost every photographer owned a 50mm f/1.8 prime lens and in many cases it was the lens with which a camera body was sold. Key to the success of such lenses was the fact that their coverage, on a full-frame camera, matched that of the human eye. This same advantage does not apply to Sony's latest lens owing to the fact that it is designed exclusively for APS-C coverage: this restricts its angle-of-view to that of a 75mm lens on a full-frame camera, turning the 50mm lens into one that is ideal for environmental portraiture.

Sony has packed its 50mm f/1.8 lens into a tiny and lightweight, yet very usable, package. The only problems relate to the focusing ring; its small size hampers manual use and its rotation in AF mode forces the user to take a more rearward grip than is truly comfortable. Unlike its 50mm f/1.4 sibling, this lens has a selector on its barrel for switching between AF and manual mode. However, despite the addition of a Smooth AF Motor (SAM) automatic focusing remains a little noisy although manual focusing has an even smoother feel than on the f/1.4 lens.

MTF testing produced some impressive results. There is a slight dip wide-open but stopping down to f/2.8 is sufficient to boost the resolution to nearly 0.3 cycles-per-pixel. The lens peaks above 0.35 cycles-per-pixel at f/5.6 and remains above 0.25 cycles-per-pixel right out to f/22. Just as importantly, the colour curves are very tightly grouped and there is not even a hint of chromatic aberration. Slight distortion can be detected numerically but this is neither significant nor visible in real-world pictures.

It is a shame that there is no lens hood supplied with the lens and absence of an external bayonet, owing to the concertina nature of the lens extension, means that a separately-purchased hood will have to be screwed onto the lens and stowed separately when not in use. Nikon used to offer (and maybe still does) a collapsible rubber hood that would be ideal for lenses such as this were it not for the fact that Nikon standardised on a 52mm filter thread and Sony's lens features an even smaller.