Sony NEX-5N Optics
Sony NEX-5N Optics
The Sony NEX-5N is available either body-only, or bundled with an 18-55mm f/3.5-5.6 zoom lens that offers 35mm-equivalent focal lengths from 27 to 83mm. With the kit zoom mounted, the NEX-5N is rather too bulky to be considered pocketable, although it's still a fair bit smaller than the typical consumer SLR with a similar lens. Sharpness is about average, while autofocus is fairly quick, quiet and well-suited to movie capture, and the Optical SteadyShot image stabilization proves useful, especially towards the telephoto end of the zoom range. In the in-depth tests performed at our sister site, SLRgear, we did find some issues with chromatic aberration towards the middle of the zoom range, as well as distortion at most focal lengths, however. More details can be found in our SLRgear.com review.
Like all NEX-series cameras, the Sony NEX-5N features a Sony E lens mount. Thanks to its use of an APS-C sized image sensor, the NEX-5N has a 1.5x focal length crop.
Although it's still a fairly young system, there's quite a healthy selection of glass available for E-mount cameras. As of this writing (November 2011), Sony offers seven E-mount lenses: three zooms that together cover a range from 18-210mm (27-315mm equivalents), and four primes from 16mm to 50mm (24mm to 75mm equivalents.) For the zoom lenses, all are stabilized. Among the primes, only the 50mm lens offers stabilization. There's also one lens carrying Carl Zeiss branding, the Sonnar 24mm f/1.8, which is tied with the 50mm prime as brightest first-party lens available for the E-mount.
In full, the list of E-mount lenses available from Sony is as follows:
|Sony E-mount lenses|
Sony E 18-55mm f/3.5-5.6 OSS (27-83mm equivalent)*
Sony E 18-200mm f/3.5-6.3 OSS (27-300mm equivalent)
Sony E 55-210mm f/4.5-6.3 OSS (83-315mm equivalent)
Sony E 16mm f/2.8 (24mm equivalent)
Carl Zeiss Sonnar T* ZA 24mm f/1.8 (36mm equivalent)
Sony E 30mm f/3.5 (45mm equivalent)
Sony E 50mm f/1.8 OSS (75mm equivalent)
* available as a kit lens
In addition, two conversion lenses which can be mounted on the front of the 16mm prime increase the wide-angle possibilities for E-mount photographers still further, to either 15mm or 18mm equivalents. It's also possible to use Alpha-mount lenses (including older glass from Minolta and Konica-Minolta) with the NEX-5N, using either the LA-EA1 or LA-EA2 mount adapters.
Beyond the optics and adapters provided by Sony themselves, a wide variety of third-party options are also available. Sony has been uncommonly open with its E-mount, providing basic specifications to lens and mount adapter manufacturers without fee, and while that hasn't yet resulted in a flurry of third-party lenses, there are a vast array of mount adapters available that allow use of lenses from most common mounts. If you have a lens from a mount that's at least reasonably well-known, chances are an adapter will be available; there are so many that it's really beyond the scope of this review to attempt to cover them all. Suffice to say that there will be limitations in their use, however -- most notably with the lack of autofocus, and with vignetting on lenses designed to provide an image circle smaller than the NEX-5N's APS-C sized image sensor.
Third party lenses, at this time, are all completely manual, and include an 8mm fisheye from Korea's Samyang Optics, plus three primes (28mm f/2.8, 35mm f/1.7, and 50mm f/0.95) from Hong Kong's SLR Magic / Noktor. Japan's Sigma Corp. showed prototype lenses for the E-mount in early 2011, but has yet to release any products. A number of other manufacturers have expressed interest, but likewise have yet to release any E-mount lenses.
There are two approaches to mechanical image stabilization in compact system cameras: lens-based, or in-body (sensor shift). For the NEX series models, including the 5N, Sony has opted for a lens-based system, branded as "Optical SteadyShot". One of the main advantages of lens-based stabilization in SLRs--the fact that the optical viewfinder image is also stabilized--doesn't apply in compact system cameras, since they're always operating in live-view mode, thus allowing sensor shift systems likewise to provide a stabilized preview. Still, lens-based stabilization typically performs better at longer focal lengths than do sensor-shift systems. There is a drawback, though: with a lens-based system, you must decide whether to opt for a stabilized version of each lens, and pay a premium for the stabilization, where in-body systems offer stabilization with pretty-much any lens.
As with all currently-available E-mount zoom lenses from Sony, the 18-55mm kit lens is stabilized. With the exception of the 50mm f/1.8, none of the current primes are stabilized. When using Alpha-mount lenses with the optional mount adaptors, stabilization is not available, since Sony's Alpha-series image stabilization relies on sensor shift ("SteadyShot Inside") technology inside the camera body, something that's not available in NEX-series bodies.
Like any compact system camera, the NEX-5N's lack of a mirror box means that there's nowhere in the optical path to put a dedicated phase detection sensor. Instead, the NEX-series cameras are reliant on the image sensor itself for autofocus. This means using contrast detection autofocus, by default, as do all mirrorless models except Nikon's J1 and V1. (Those cameras don't have a dedicated phase detect sensor, but include phase detection AF points on the main imaging sensor.) Sony's E-mount lenses were designed from the ground up with contrast detection autofocus performance in mind, with the weight and positioning of the focusing group tuned appropriately, and focus drive is provided by a near-silent stepper motor. This, along with the increased processing power of modern cameras, means that contrast detection autofocus is a much more useful proposition than was the case a couple of years ago, although it's typically still somewhat slower than phase detection. The advantage of contrast detection, though, is that it negates problems with front or back focusing, and generally provides higher autofocus accuracy.
Some Alpha-mount lenses attached via the LA-EA1 mount adapter that's running current firmware can also be used with the NEX-5N's contrast detection autofocus system, but only if they use an in-lens autofocus motor. That rules out screw-drive lens models, which must be focused manually when using this adapter. Since Alpha-mount lenses weren't designed with contrast detection autofocus operation in mind, performance may suffer to varying degrees--depending on the lens model--both in terms of AF speed and power consumption. If shooting video, lens drive noise may prove objectionable.
With the alternate LA-EA2 mount adapter, the NEX-series cameras are uniquely able to provide for phase detection autofocusing with Alpha-mount lenses, courtesy of a dedicated phase detect sensor. They do this in basically the same way as Sony's Translucent Mirror-based SLT-series cameras. A partially reflective mirror is placed in the optical path, sending a portion of incoming light to the dedicated 15-point autofocus sensor. Unlike the earlier mount adapter, the LA-EA2 provides support for screw-drive lenses, thanks to a built-in autofocus motor. Since it doesn't rely on the stepped motion of contrast detection AF, it should also provide significantly better AF performance even with lenses that include their own AF motors. Of course, AF drive noise may still prove an issue, depending on the lens model in use.
When using the LA-EA2 mount adapter, the NEX-5N offers a focus micro adjustment feature, allowing an adjustment within an arbitrary -20 to +20 step range to be dialed in for up to 30 separate lenses. The adjustment is specific to the lens model, and not to the serial number -- that is to say, if you have two identical lenses, the adjustment dialed in for one will also apply to the other.
The Sony NEX-5N includes a bright orange LED lamp, just inside the top of the hand grip, which serves as an AF assist illuminator. With relatively limited space available on the body, it's quite easy to accidentally obscure with your fingertips, especially if you have large hands. It's also likely to be obscured by larger lenses, and can't be used with Alpha-mount lenses attached via the LA-EA2 mount adapter. It serves its purpose quite well for nearby subjects with the kit lens, however.
The Sony NEX-5N features an electromagnetic vibration dust-reduction system, coupled with a charge protection coating on its low-pass filter that aims to prevent dust adhering -- especially important since the NEX-5N's shutter is normally open for full-time Live View. The vibration seems to be at a higher frequency than in past NEX cameras, because it's no longer clearly audible when operating. (At launch, Sony described the dust reduction system as being new, and used the term "ultrasonic vibration" for the first time, backing up--but not definitively confirming--this assumption.) The system automatically runs only at power-off, meaning that it doesn't delay camera startup. It can also be triggered at any time while using the camera, should you notice that dust specks are present in your images.
Sony NEX-5N Optical Test Results
Below are the results of our optical tests with the Sony NEX-5N and the bundled E 18-55mm f/3.5-5.6 OSS kit lens. The test images shown on most other pages of this review were taken with very sharp references lenses, so we use this page to explore kit lens quality.
Lens Test Results
Typical performance with the E 18-55mm OSS kit lens.
|18mm @ f/8||55mm @ f/8|
The Sony NEX-5N is available bundled with an E-mount 18-55mm f/3.5-5.6 OSS lens. This lens possesses a very typical optical zoom ratio of about 3x, with a 35mm equivalent focal range of about 27-83mm because of the NEX-5N's 1.5x "crop factor". Sharpness and contrast at wide-angle were pretty good at f/8. Chromatic aberration is very low, but that's because the NEX-5N corrects for it by default (see below), though some flare is visible around the building's white surfaces. Results at the 55mm setting were also pretty good at f/8, with just a touch of flare. See below for comments on macro performance, geometric distortion, corner softness, etc.
An average sized minimum coverage area, with very good detail. Flash throttled down well.
|Macro with 18-55mm kit lens
(55mm @ f/8)
|Macro with Flash
(55mm @ f/8)
As with zoom performance, the Sony NEX-5N's macro performance will depend entirely on the lens in use. However with the E 18-55mm kit lens set to 55mm, the NEX-5N captured an average sized minimum area measuring 2.98 x 1.98 inches (76 x 50 millimeters). Detail was quite good in the center, though corners and edges were quite soft (most lenses have some softening in the corners at macro distances), and the NEX-5N's Auto white balance rendered the shot with a yellow/green cast. The flash did a very good job throttling down resulting in a well-exposed image, and had no trouble clearing the lens as there is no detectable shadow.
Higher than average geometric distortion at wide-angle and telephoto.
|Barrel distortion at 18mm is 1.1 percent|
|Pincushion distortion at 55mm is 0.5 percent|
The Sony NEX-5N's E 18-55mm kit lens produced about 1.1 percent barrel distortion at wide-angle, which is higher than average and noticeable in some of its images. At the telephoto end, there's about 0.5% pincushion distortion, also higher than average and noticeable in some images. This is the tendency for the lens to bend straight lines outward (like a barrel -- usually at wide-angle) or inward (like a pincushion -- usually at telephoto).
Unlike previous NEX models, the NEX-5N can apply geometric distortion correction to JPEGs. See the Lens Corrections section below.
Chromatic Aberration and Corner Sharpness
Moderately low chromatic aberration at wide-angle; even lower levels at full telephoto. The lens produced some soft corners wide-open, though corner sharpness was quite good stopped-down.
Chromatic Aberration. Chromatic aberration in the corners with the NEX-5N's 18-55mm kit lens at wide-angle (18mm) is moderate in terms of the number of pixels, but not very bright, so the effect isn't very noticeable in some shots. At full telephoto (55mm), CA is also moderate in terms of pixels, but the colors in the fringes are even more muted, partially due to a loss of contrast. Color fringing gradually reduces in brightness and width as it approaches the center of the image, where it is very low at wide-angle and telephoto. Note that the NEX-5N corrects for CA by default though. See the Lens Corrections section below for details.
Corner Softness. Wide-open at full wide-angle, the copy of the 18-55mm kit lens that came with our NEX-5N was a little soft in all four corners, with the the left corners slightly softer than the right. What little softness there was extended pretty far into the frame. The center of the image was sharp with very good contrast. Some vignetting (corner shading) is also noticeable at full wide-angle, as indicated by the darker corner crop. At full telephoto, corners were also soft and the lens had lower contrast overall.
"Stopped-down" to f/8, performance in the corners at wide-angle improved quite a bit compared to wide-open at f/3.5, with noticeably better sharpness in the corners. At telephoto, corners were also much sharper, with better contrast than wide-open. Very good results here.
When shooting in JPEG mode, the Sony NEX-5N includes the ability to automatically correct for geometric distortion, chromatic aberration, and lens shading (vignetting), as images are captured. Only E-mount lenses are supported, and RAW files are not corrected.
|Barrel distortion at 18mm is 0.3 percent|
|Pincushion distortion at 55mm is <0.1 percent|
Above, you can see with Distortion Correction enabled (set to Auto), the kit lens shows significantly less distortion (+0.3% at wide-angle, <-0.1% at telephoto) than with it disabled (+1.1% at wide-angle, -0.5% at telephoto). The default setting is Off.
|CA Correction Auto||CA Correction Off|
|18mm@f/3.5: Lower left
C.A.: Moderately low
|18mm@f/3.5: Lower left
|55mm@f/5.6: Upper left
C.A.: Very low
|55mm@f/5.6: Upper left
Above, you can see a significant increase in CA at wide-angle with CA Correction disabled, though the difference at telephoto is minimal because CA is low at telephoto to begin with. The default setting is Auto.
|18mm @ f/3.5|
Mouse-over the links above to see the difference Lens Shading correction makes at wide-angle when wide-open at f/3.5 (the worst-case scenario for most lenses). The default setting is Auto.
The images above were taken from our standardized test shots. For a collection of more pictorial photos, see our Sony Alpha NEX-5N Photo Gallery .
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