Following Fujifilm’s strategy Sony started the FE system by releasing mostly high priced lenses first. Regarding their comparatively expensive full-format cameras, this was certainly a sensible approach. However, now that the initial quality rush is over, Sony is beginning to offer more affordable lenses for the rest of us. The Sony FE 50mm f/1.8 is one of them. That being said, Sony lenses have never been really cheap. In this case we are talking about the double price tag of its Canon/Nikon counterparts or about 300US$/EUR. That’s quite a bit considering the fact that the lens has a simple optical and mechanical design. However, it is 3(!) times cheaper than its in-house mate, the Zeiss FE Sonnar T* 55mm f/1.8 ZA, so there’s still a certain point for Sony users.
The build quality of the Sony lens is pretty good. The lens body is made of the good quality plastics based on a metal mount. Typical for its species it is very light-weight at just 186g. The focus ring operates smoothly. The inner lens tube extends by about 1cm when focusing to the minimum focus distance (0.45m) – thus rather than using an inner focusing mechanism, it uses a so-called “linear extension” approach. A barrel-shaped lens hood is also part of the package.
Regarding the AF system – let me cite Sony first: “A new DC motor drive system has been carefully designed and implemented for optimum focus precision and speed as well as quiet operation.”. My turn: it’s crap! I’m sorry to say but there is no other word for that. Upon first contact I thought Sony made a joke there. These days AF motors are usually noiseless and pretty speedy but the Sony FE 50mm f/1.8 just isn’t. The (admittedly moderate) noise level may be acceptable but the AF speed is downright dismal. Some accountant in Sony seems to have thought that spending 5 dollars more for a decent AF motor was just not worth it. Message to Sony – at least certain key aspects should not be left to accounting really. As usual manual focusing works “by wire” thus you are driving the (slow!) autofocus motor by turning the focus ring (did I mentioned it’s slow?).
| Specifications | |
|---|---|
| Optical construction | 6 elements in 5 groups inc. 1x aspherical element |
| Number of aperture blades | 7 (circular) |
| min. focus distance | 0.45m (1:7.1) |
| Dimensions | 68.6×59.5 mm |
| Weight | 186g |
| Filter size | 49mm |
| Hood | supplied, barrel-style, bayonet mount |
| Other features | – |
Distortion
Standard lenses are usually pretty much free of image distortions and this also applies to the Sony lens. The numeric figure (below) determined by Imatest is quite impressive for sure.
Vignetting
At fully open aperture, the light falloff reaches a very hefty ~2.8EV (f-stops) – this is immediately noticeable. To be fair, this is simply the typical amount of vignetting for such lenses on full-format cameras. Stopping down to f/2.8 results in a substantial improvement (1.1EV) but if it’s an issue it’s best to stop down to f/4 from where on the vignetting isn’t objectionable anymore.
Please note that vignetting can be auto-corrected both in the camera or via various RAW converters out there. Due to the signal amplification this comes at cost of increased sensor noise noisy in the corners though.
MTF (resolution)
The resolution is a bit of mixed bag. The good news is the very impressive center performance. It’s very good at f/1.8 and that’s including high (local) contrast. The near-center is still good but the outer image region is downright dismal with heavily smeared corners. Stopping down to f/2.2 has little effect here. The first substantial improvement is visible at f/2.8 resulting in an excellent center and very good borders whereas the extreme corners remain very soft. f/4 provides a massive gain in performance across the image field – including very good corners. The peak quality is reached around f/5.6. Visible diffraction effects reduce the quality perception from f/11 onward again.
The centering quality of the tested sample was acceptable.
Please note that the MTF results are not directly comparable across the different systems!
Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure of sharpness. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations.
Chromatic Aberrations (CAs)
The Sony lens produces a very low amount of lateral CA (color shadows at harsh contrast transitions) with an average CA pixel width around 0.6px at the image borders. This is impressive on a 42mp sensor.
Bokeh
The bokeh describes the rendition of out-of-focus blur in the focus transition zone – thus the area just beyond the depth-of-field. This is sometimes misunderstood – it is NOT about the blur of the far background. If the focus spread between your main object and the surroundings are big enough, pretty much any lens can produce a smooth blur.
The Sony FE 50mm f/1.8 has a fairly decent bokeh quality.
Out-of-focus highlights have a circular shape at f/1.8 to f/2.8 (just) with a very smooth the inner zone albeit slight outlining. The outlining effect is emphasized when stopping down.
As usual the highlight discs deteriorate to “cat’s eyes” towards the corners but this is a rather normal behavior in the full format scope and somewhat less pronounced than usual.
Stopping down helps to tame this aspect – at the expense of more edgy highlight discs.
The general blur is reasonably smooth. The two sample crops below (background vs foreground) are positioned to the left and right of the image center respectively. If you look closely, you may spot that the blur is smoothing towards the center rather than symmetrically (visible at the black clubs and red diamonds). There is some smearing in the image corners.
Bokeh Fringing / Longitudinal Chromatic Aberrations (LoCA)
So-called bokeh fringing is an effect that occurs around the focus point (on the Z-axis). It’s visible as halos of different colors in out-of-focus areas – magenta (red + blue) in front of the focus point and green beyond.
The Sony lens exhibits a significant amount of bokeh fringing at f/1.8 and it’s still obvious at f/2.2 and f/2.8. An substantial improvement can be seen at f/4 and the effect is essentially gone at f/5.6.
On the downside you may spot that the focus point moves to the back when stopping down. These are so-called residual spherical aberrations or in plain English – focus shifts.
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Some readers were a bit astounded by the following image from our sample image section.
Please note that this was a STRESS TEST with extreme contrasts!
You may spot the rather excessive degree of fringing in there – greenish in the background and purplish in the foreground. This is primarily bokeh fringing/LoCAs although there’s certainly also a hint of “purple fringing” in there (a blooming effect). Please note that you can push many lenses into this behavior if you just want to.
Sample Images
It is a bit difficult to come to a conclusion about the Sony FE 50mm f/1.8. It has its moments but there's also darkness. The resolution characteristic is fairly solid. The outer image field is very soft at large apertures but to be fair - your main subject tends to be near the image center so it's probably not all that of a deal-breaker in the real life. The center itself is already very sharp and contrasty at f/1.8. The situation is very different between f/4 and f/8 where the quality is impressive indeed. Lateral CAs are generally not an issue.
The lens produces some heavy vignetting at maximum aperture. Some may like this effect as a creative element but those who don't may prefer to correct this either via camera setting or in your favorite RAW converter. Otherwise you should stop down by about 2 f-stops. The quality of the bokeh is fairly good with smooth highlight discs, albeit with a bit of outlining, and a smooth albeit asymmetric general blur. A fair share of bokeh fringing is also present (see one rather extreme example in the sample image section).
The mixture of good and bad continues on the mechanical side. The build quality is actually very decent and in line with most modern 50mm f/1.8 lenses. There's a pain point though - the auto-focus. Some lenses get nicknames and we'd like to call this one "Captain Slow" (we hope James May doesn't mind …). It is embarrassing to witness such an AF in a brand new lens really.
Which brings us the question whether this lens is worth it? We are not convinced.
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Optical Quality
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Build Quality
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Price / Performance