Sony FE 50mm f/1.8 SEL50F18F
Lab Test Results
June 15, 2016
by Andrew Alexander
Sony has had various 50mm lenses in A-mount configurations for a number of years, including a couple 50mm ƒ/1.4 offerings and an APS-C-specific 50mm ƒ/1.8. However, there wasn't an affordable "nifty fifty" lens for Sony's full-frame mirrorless cameras, until the FE 50mm ƒ/1.8 debuted in March 2016.
The lens design is 6 elements in 5 groups, with a single aspherical lens. Seven rounded aperture blades make up the diaphragm, which should give pleasing results for out-of-focus elements in a captured image.
The Sony FE 50mm ƒ/1.8 accepts 49mm filters, ships with th ALC-SH146 round lens hood, and is available now for around $250.
Given the lens' maximum aperture of ƒ/1.8, it's likely that many people will want to shoot at that aperture setting. If you're looking for edge-to-edge sharpness, you won't find it at ƒ/1.8; you have to stop down significantly. At ƒ/1.8, the lens provides decent results for sharpness in a very small central region of the frame, and on a full-frame camera, the corners are decidedly soft. On an APS-C camera, the soft corners are excluded from capture simply because the sensor isn't wide enough to see them.
Stopping down is necessary to extract maximum sharpness from this lens. Going to ƒ/2.8 produces much more central sharpness, but soft corners are still present; only by ƒ/4 do we start to see excellent sharpness from corner to corner. There's further improvement at ƒ/5.6, and by ƒ/8, an image is tack-sharp from one corner to the other.
Diffraction limiting begins to set in at ƒ/11, but it's not really noticeable until until the aperture is fully stopped-down at ƒ/22 and we see a generalized softness across the frame.
According to our test graphs, the Sony FE 50mm ƒ/1.8 does an excellent job of controlling lateral chromatic aberration, and our review of the sample images bears this out. We've noticed in the past that fast prime lenses sometimes exhibit exaggerated spherical chromatic aberration when the lens is used at its widest aperture, and to a small extent that's present with the Sony FE 50mm ƒ/1.8:
With the Sony FE 50mm ƒ/1.8 mounted on a sub-frame camera, corner shading isn't really an issue -- we only note corners which are 1/3 EV darker than the center, when the lens is set to ƒ/1.8.
Mounted on a full-frame camera, however, we see some serious corner shading: at ƒ/1.8, the corners are over a full stop darker than the center. Stopping down to ƒ/2.8, this corner shading is around a half-stop, and by ƒ/4, corner shading is negligible.
There's very little image distortion to speak of when using the Sony FE 50mm ƒ/1.8.
The Sony FE 50mm ƒ/1.8 employs a new DC motor which provides "optimum focus precision and speed as well as quiet operation." It's not a fast motor -- it can take well over a second to go from close-focus to infinity -- but small changes in focus are relatively speedy. It's also not as quiet as other autofocus systems, and Sony cautions that "Focus motor sound may be recorded when shooting movies." The front element doesn't rotate during autofocus, which is good for polarizer users.
Build Quality and Handling
The FE 50mm ƒ/1.8 follows the same design aesthetic as Sony's other new mirrorless lenses, with a sleek, matte black barrel design with modern, sharp edges. The lens barrel is constructed out of sturdy yet lightweight plastic. There are no external markings or features like a focus distance scale or AF/MF switch -- the only thing on the lens other than the focusing ring is the lens' denomination - FE 1.8/50.
The 3/4-inch-wide focus ring has many fine grooves, which provide an excellent feel and a secure grip. The focus system is all electronic, so the focus ring itself rotates continuously with no stops on either end. The rotational action is very smooth with just the right about of resistance for controllable and precise focus adjustments. Focus adjustments don't rotate the front element of the lens (and thus any attached 49mm filters), and since the lens employs internal focusing, the size of the lens doesn't change.
The ALC-SH146 lens hood ships with the lens -- a round, bayonet-mounted hood that adds over an inch to the lens' length when attached. It can be reversed and mounted for storage, and the interior is a matte black to help reduce lens flare.
Sony FE 55mm ƒ/1.8 ZA Carl Zeiss Sonnar ~$900
Optically, the performance is almost identical between this lens and the Sony FE 50mm ƒ/1.8; for sharpness, the Carl Zeiss 55mm has much better corners at wider apertures, but it's slightly bigger and more expensive.
Sigma 50mm ƒ/1.4 DG HSM Art ~$950
Sigma offers a 50mm ƒ/1.4 in its Art lineup in the Sony A-mount, meaning you'd need to use an adapter. It is substantially more expensive than the $250 Sony FE 50mm ƒ/1.8, however optically, the Sigma lens is a real winner: it's tack-sharp at ƒ/2, for example.
As an economical way to get a "nifty fifty", the average Sony user probably won't complain about the Sony FE 50mm ƒ/1.8: at $250, it's one of Sony's least expensive lenses, though compared to other manufacturers, there is still a premium price.
Optically, the lens can perform extremely well, but for edge-to-edge sharpness you have to stop down to ƒ/8, which runs against the lens' allure as a fast prime lens offering a wide-open aperture of ƒ/1.8. Personally, I don't necessarily see this as a failing, as most images require some form of subject isolation, and the extra softness on the edges actually works for you in this regard. Just be aware that if you need absolute image sharpness, you'll need to stop down to ƒ/8. And if you're shooting on something like the A7r II, with 42 megapixels, your technique has to be rock-solid.
Otherwise, there's a lot to like in this small, inexpensive package, and Sony's done well here.
The VFA target should give you a good idea of sharpness in the center and corners, as well as some idea of the extent of barrel or pincushion distortion and chromatic aberration, while the Still Life subject may help in judging contrast and color. We shoot both images using the default JPEG settings and manual white balance of our test bodies, so the images should be quite consistent from lens to lens.
As appropriate, we shoot these with both full-frame and sub-frame bodies, at a range of focal lengths, and at both maximum aperture and ƒ/8. For the ''VFA'' target (the viewfinder accuracy target from Imaging Resource), we also provide sample crops from the center and upper-left corner of each shot, so you can quickly get a sense of relative sharpness, without having to download and inspect the full-res images. To avoid space limitations with the layout of our review pages, indexes to the test shots launch in separate windows.
Sony FE 50mm f/1.8 SEL50F18F
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