Introduction

Ease of Use

The Sony DT 50mm F1.8 SAM lens mounted on a Sony A77

Weighing in at a mere 170 grams, the plastic-bodied Sony DT 50mm F1.8 SAM is a lightweight prime A-Mount lens that is a little dwarved by the Sony A77 body that we tested it with, as shown in the photos below. It's therefore perhaps a better match for one of Sony's smaller APS-C cameras. Note that this lens is not compatible with Sony's full frame DSLRs.

The Sony DT 50mm F1.8 SAM lens mounted on a Sony A77

The Sony DT 50mm F1.8 SAM lens mounted on a Sony A77

The Sony DT 50mm F1.8 SAM lens alongside a Sony A77

Front of the Sony DT 50mm F1.8 SAM lens

Build quality is unexpectedly good considering the relatively low price of the lens. The Sony DT 50mm F1.8 SAM has a distance scale in feet and meters, useful when manually focusing, but there's no depth-of-field scale or infrared index.

Front of the Sony DT 50mm F1.8 SAM lens

Front of the Sony DT 50mm F1.8 SAM lens, isometric view

The Sony DT 50mm F1.8 SAM has a rather thin and smooth zoom ring. It takes a 120 degree turn to change the focus from close-up to infinity, with the lens extending by an extra 2cm when set to the closest working distance of 34mm. The focus ring is just over 1cm wide and features handy stops at either end of the distance scale.

Rear of the Sony DT 50mm F1.8 SAM lens

There's also a switch to change between auto and manual focus.

Rear of the Sony DT 50mm F1.8 SAM lens, isometric view

Focusing is usefully internal and the Sony DT 50mm F1.8 SAM lens has a plastic lens mount and accepts 49mm filters via plastic threads.

No lens hood is supplied with the lens or available as an after-market item, although the internal nature of the lens construction partly makes up for this omission.

Focal Range

At the 50mm focal length the angle of view is 83 degrees.

  Field of view at 50mm

Focusing

The Sony DT 50mm F1.8 SAM lens has quite a narrow focus ring. There are hard stops at both ends of the range, making it straight forward to set focus at infinity. Polariser users will be pleased to learn that the 49mm filter thread does not rotate on focus.

When it comes to auto-focusing, the Sony DT 50mm F1.8 SAM zoom is quite a quick performer, taking about 0.25 seconds to lock onto the subject when mounted on the Sony A77 that we tested it with. Note that it is noisy though, with an audible whirring, so it's not best suited to more candid shots in a quiet environment.

We didn't experience much "hunting" though, either in good or bad light, with the lens accurately focusing almost all of the time.

Chromatic Aberrations

Chromatic aberrations, typically seen as purple or blue fringes along contrasty edges, are only apparent in a couple of our test shots taken with the A77 body.

Light Fall-off

With the lens set to its maximum aperture, there is quite a lot of light fall-off in the extreme corners, as shown below.

Light fall-off at 50mm

Macro

The Sony DT 50mm F1.8 SAM isn't claimed to be a macro lens, offering a minimum focusing distance of 34cm and a maximum magnification of 0.2x. The following example demonstrates how close you can get to your subject, in this case a Compact Flash memory card.

Close-up performance

Bokeh

Bokeh is a word used for the out-of-focus areas of a photograph, and is usually described in qualitative terms, such as smooth / creamy / harsh etc. In the Sony DT 50mm F1.8 SAM lens, Sony employed an iris diaphragm with seven rounded blades, which has resulted in very appealing bokeh in our view. We do realise, however, that bokeh evaluation is subjective, so we've included several 100% crops for your perusal.

Sharpness

In order to show you how sharp this lens is, we are providing 100% crops on the following page.