Sony FE 40mm f/2.5 G (SEL40F25G) lens
Small, light weight and weather-resistant makes the Sony FE 40mm f/2.5 G a good general-purpose lens. It won’t take up much space in a bushwalker or traveller backpack and won’t weigh the photographer down.
It is also ideal for use on gimbals and with drone cameras.
The FE 40mm f/2.5 G (SEL40F25G) lens is the second of Sony’s trilogy of compact prime lenses announced in late March, 2021 for us to review, following the FE 24mm f/2.8 G (SEL24F28G) lens. One third of a stop faster and not quite as wide, it boasts similar features with a de-clickable aperture ring for video use, an AF/MF switch on the lens barrel and a focus hold button that gives rapid access to focus mode settings. All three lenses are dust-and moisture-sealed and have fluorine coatings on their front elements to repel water, dust and grease and make the lens easy to keep clean.
Angled view of the FE 40mm f/2.5 G (SEL40F25G) lens without the supplied lens hood. (Source: Sony.)
The optical design of this lens (shown below) is relatively simple, consisting of nine elements in nine groups, with three aspherical elements. The iris diaphragm has seven blades, which are curved to produce a near circular aperture as the lens is adjusted, creating pleasing bokeh quality.
This diagram shows the positions of the exotic glass elements in the optical design of the Sony FE 40mm f/2.5 G lens. (Source: Sony.)
A linear motor plus an internal focusing design ensure fast, quiet and accurate autofocusing allowing this lens to be used for video recording. In addition, the Linear Response manual focus control and AF/MF switch on the lens barrel allow more tactile control, while the focus hold button gives rapid access to focus mode settings.
Also for video use, the aperture ring can be de-clicked to allow smooth, silent aperture readjustment. All three lenses in the series are dust-and moisture-sealed and have fluorine coatings on their front elements to repel water, dust and grease and make the lens easy to keep clean.
The innovative ALC-SH166 lens hood for the FE 40mm f/2.5 G and FE 50mm f/2.5 G lenses. (Source: Sony.)
This lens is supplied with front and end caps plus the ALC-SH166 lens hood, shown above, which fits onto the front of the barrel with the normal bayonet mounting. Unusually, it pinches inwards instead of flaring out like many hoods for wide-angle lenses.
It can’t be reversed over the lens, but it is small enough for this not to matter and it provides excellent protection against both stray light and impact damage. Red index marks on both hood and lens make it easy to fit and remove.
Who’s it For?
It’s difficult to find a specific purpose for a 40mm lens; its angle of view isn’t quite wide enough for landscapes but too wide for portraits. It’s too short for sports – with the possible exception of indoor games where a general view of the action is needed. At a pinch it could be used for street photography and some photojournalism, although in both cases a short-to-medium zoom would be better.
As part of Sony’s matched trio, it could fill in the gap between the 24mm and 50mm lenses. But a fair amount of lens swapping would be required. It would also be usable with drone cameras and gimbals, where its small size and light weight would be advantageous. Sony also claims the 40mm angle of view is ideal for movie shooting as it corresponds to the natural field of vision.
Build and Ergonomics
Like its siblings the FE 40mm f/2.5 G is made mainly from aluminium alloy, with an engraved Sony logo and focal length designation on the barrel plus threading around the front of the lens that accepts the same 49 mm filters as the other two lenses. the three lenses look almost identical, as shown in the illustration below.
The main distinguishing feature for the trio of lenses is the focal length designation engraved on the lens barrel.
At the front of the lens barrel is the focusing ring, which is 8 mm wide and entirely covered with moulded ridging. Since focusing is driven from the camera, this ring turns through 360 degrees when power is off.
Roughly 2 mm behind the focusing ring is the aperture ring, which is marked in increments starting at f/2.5 on the right, followed by f/4 then with one-stop gaps to f/22 on the left, which click-stops at 1/3-stop intervals. A red ‘A’ mark beyond the f/22 setting denotes the auto aperture setting. It takes effect seamlessly when the camera is set to the P and auto shooting modes.
Side views of the FE 40mm f/2.5 G lens showing the locations of its controls. (Source: Sony.)
Behind the aperture ring is a 10 mm wide section of the lens barrel that carries the focus button and AF/MF slider switch around the left side of the barrel and the click On/Off switch around to the right. The white index line for the aperture settings is located on this band, along with the 40 an G branding logos.
The barrel then slopes inwards and extends for another 10 mm section, which carries the index mark for mounting the lens on the camera plus additional branding data. The solid metal mounting plate is surrounded by a thin rubber gasket that seals the joint against ingress of moisture and dust.
Our Imatest tests were taken with the Sony α7 II camera to provide consistency across all three lenses in the series. Like the other lenses, the 40mm f/2.5 G lens performed well and achieved centre resolution that was comfortably above expectations for JPEG files, although resolution declined towards the periphery of the frame. Measurements taken roughly half-way towards the edges of the frame fell a little short of expectations with JPEGs, although they were above expectations for ARW.RAW files captured at the same time and converted into 16-bit TIFF format with Adobe Camera Raw.
Edge softening was common to both JPEG and ARW.RAW files with measurements taken three quarters of the way to the corner falling short of expectations – although only just short with ARW.RAW files. The best performance was at f/3.2 although, as shown in the graph of our test results below, central resolution remained high until f/6.3 when diffraction began to create a gradual reduction in sharpness.
Peripheral resolution rose gradually throughout the aperture range, with some softening evident at aperture settings through to about f/5.6. This performance can be seen as a good overall result.
Lateral chromatic aberrations in JPEG files recorded with all in-camera corrections disabled were well down in the low band, as shown in the graph of our test results above, in which the red line marks the boundary between ‘negligible’ and ‘low’ CA. We found no signs of coloured fringing in either JPEGs or raw files in our test shots and the in-camera corrections would generally correct any potential problems.
Both vignetting and rectilinear distortion could be seen in uncorrected files, although the in-camera corrections addressed them effectively. Most signs of vignetting had gone by f/4 but traces remained through to f/5.6. Very slight barrel distortion was present at all aperture settings but you had to look hard to notice it.
The review lens handled backlit subjects quite well and resisted flaring under most conditions. Flaring could be forced by pointing the camera at a bright light source but it was relatively slight, thanks in part to the effective lens hood. Nice, 14-pointed sunstars were possible at f/22.
The minimum focus is not close enough to make this lens useful for close-up work, although with careful framing it can produce acceptable close-ups of larger flora and fauna. Bokeh in wide-aperture shots is influenced by background lighting, becoming fragmented and choppy in uneven illumination. Highlight outlining was common and circular highlights became a little oval-shaped towards the edges of the frame.
We found no issues with autofocusing, save for slight focus breathing which made the image a little larger at close distances. It’s debatable whether this would be significant for most users.
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Picture angle: 57 degrees
Minimum aperture: f/22
Lens construction: 9 elements in 9 groups (including 3 aspherical elements)
Lens mounts: Sony FE
Diaphragm Blades: 7 (circular aperture)
Weather resistance: Yes; dust and moisture resistant
Focus drive: Linear motor with internal focusing
Stabilisation: Relies on IBIS in Sony’s cameras
Minimum focus: 28 cm (AF), 25 cm (MF)
Maximum magnification: x 0.2 (AF),x 0.23 (MF)
Filter size: 49 mm
Dimensions (Diameter x L): 68 x 45 mm
Weight: 173 grams
Standard Accessories: Front and rear caps plus ALC-SH166 lens hood
Distributor: Sony Australia; 1300 720 07
Based on JPEG files recorded with the Sony α7 II camera.
Based on RAW-RAW files recorded simultaneously and converted into 16-bit TIFF format with Adobe Camera Raw.
All test shots taken with the Sony α7 II camera.
Vignetting at f/2.5.
ISO 100, 1/100 second at f/14.
Crop from the above image magnified to 100% showing little evidence of coloured fringing.
Close-up at f/2.5, 1/640 second at ISO 100.
Close-up at f/2.5 showing choppy bokeh and outlined highlights, 1/2000 second at ISO 100.
Backlit subject; ISO 100, 1/50 second at f/22.
Sunstar with slight veiling flare; ISO 100, 1/100 second at f/22.
ISO 100, 1/60 second at f/16.
ISO 200, 1/60 second at f/11.
ISO 100, 1/100 second at f/11.
ISO 100, 1/320 second at f/5.6.
ISO 200, 1/80 second at f/5.
ISO 160, 1/60 second at f/9.
ISO 160, 1/100 second at f/4.5.
ISO 160, 1/100 second at f/5.
ISO 250, 1/60 second at f/16.
RRP: AU$999; US$599
- Build: 8.9
- Handling: 8.9
- Image quality: 8.9
- Autofocusing: 8.9
- Versatility: 8.8