50mm lens test – Introduction

For many years, the 50mm focal-length lens was a staple of photography. Not only was it the optic of choice for many photographers, but with virtually every new SLR coming paired with a 50mm lens it was also many people’s first – and sometimes only – lens.

The reason for the popularity of such optics was that the 50mm focal length best replicates the focal length and central field of view of the human eye. The design was usually simple, with a minimal amount of glass, so, as a result, 50mm lenses are among the sharpest ever made, and virtually free from curvilinear distortions. This focal length also means that large apertures are possible without
the need for gigantic glass optics.

The reign of the 50mm lens ended in the 1980s when manufacturers began to offer SLRs with modest zoom lenses, and as these became more affordable they were soon the norm. However, despite the fact that many photographers now opt for complex zooms, the 50mm prime is still often the sharpest lens in a manufacturer’s range, and the f/1.8 varieties are also usually the cheapest. For instance, an f/1.8 can be bought new for less than £200, and used prices can even be under £100. With the 50mm focal length great for documentary, landscape and portrait images, there really is no excuse not to own one, but the question is, which one do you choose?

We have tested 12 lenses from Canon, Nikon, Pentax, Sigma, Sony and Zeiss to find out which 50mm optic is sharpest, which handles the best and which shows the least distortion. Each has been tested on an appropriate enthusiast-level camera, so the results reflect how they will work on that system.

50mm lens test – Which aperture?

Image: Lenses with an f/1.8 aperture are not only the most affordable, but also the best compromise

With a few different apertures available when choosing a 50mm lens, it can be tricky to know which one to go for. Lenses with an f/1.8 aperture are usually the cheaper, followed by the f/2.8 lenses, which are usually macros. The most expensive lenses are generally the f/1.4 models. This is due to their larger size and the fact that they require more glass.

Obviously, the difference in aperture affects the amount of light passing through the optic. A large aperture increases the ability to shoot in low light, or at a short shutter speed, but it has other advantages. Lenses are generally at their sharpest when the aperture is reduced by 2 stops. Two stops down from f/1.4 is f/2.8, meaning that an f/1.4 lens should be far sharper at f/2.8 than a lens with a f/2.8 maximum aperture. It’s a similar story with an f/1.8 lens, which should be sharper at f/2.8.

Depth of field is also affected. The f/1.4 lens offers an extremely shallow depth of field, but it won’t necessarily be very sharp at its maximum aperture. Stop it down 2 stops and not only will it have the same depth of field as a f/2.8 lens, but it should also be sharper.

The downside of lenses with a f/1.4 maximum aperture is their expense and size. In practice, the f/1.8 aperture only reduces light by 0.3EV, which for most photographers is not a significant difference.