Sony FE 40mm F2.5 G Lens Review

The Sony FE 40mm f/2.5 G is an ultra-compact prime lens that features an extremely light weight despite its rugged metal exterior construction. The 40mm focal length provides a natural-appearing angle of view, and the f/2.5 aperture is ready to tackle the low light venues and create a nicely blurred background. The price of this aesthetically beautiful lens is especially attractive.

In a single announcement, Sony introduced three compact, lightweight prime lenses that appeared to differ externally by only the numbers etched on the side.

These three lenses are highly complementary, providing a nice range of focal lengths while sharing the same filter size and consuming the same storage footprint. Attractive from a video perspective are the same dimensions and weight that minimize or eliminate gimbal rebalancing, and the geared rings are additionally beneficial for movie capture.

This review focuses on the 40mm version. Still, the non-optical attributes of these lenses are practically identical, and, aside from the angle of view coverage, the optical ones differ little.

Focal Length

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When selecting the ideal lens for a particular use, the focal length is always a primary consideration. The focal length determines the angle of view, which determines the subject distance required for the desired framing, and the distance from the subject determines the perspective.

When Sony introduced the trio of compact prime lenses covering 24mm, 40mm, and 50mm focal lengths, my first thought was, "Why 40mm?" 35mm is a far more common option, including in Sony's lineup. Perhaps that fact had something to do with the 40mm choice.

On a full-frame body, the 40mm focal length provides an angle of view that seems natural, and that aspect brings great general-purpose usefulness.

Modestly wider than the ultra-popular 50mm focal length, the 40mm focal length can be used for fashion, portraiture, weddings, documentary, street, lifestyle, sports, architecture, landscape, commercial, around-the-home, and general studio photography applications, including product photography. As you likely noted, a number of good applications for this lens include people as subjects. A 40mm lens (on a full-frame body) provides an angle of view too wide for tightly framed headshot portraits (a too-close perspective is required), but 40mm is an excellent choice for wider portrait framing, especially full-body portraits.

The 40mm focal length is greatly appreciated for video uses, including the entire above list.

To visualize where 50mm fits among other common focal lengths, I'll borrow a focal length range example from a zoom lens review.

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On an ASP-C/1.5x sensor format body, the 40mm focal length provides an angle of view similar to a 60mm lens on a full-frame sensor format body. Uses for this angle of view coincide with most uses of the 40mm focal length, with modestly tighter framing or modestly longer perspective for the same framing being the difference.

Max Aperture

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The lower the aperture number, the wider the opening, and the more light the lens will allow to reach the imaging sensor. Each "stop" in aperture change (full stop examples: f/1.4, f/2.0, f/2.8, f/4.0) increases or decreases the amount of light reaching the sensor by a factor of 2x (a substantial factor).

When you buy a prime lens instead of a zoom, you expect at least one strong advantage to offset the loss of zoom range versatility. Common prime lens advantages include smaller size, lighter weight, lower price, better image quality, or a wider aperture. The lens checks those boxes, with that last advantage being a modest one.

The three simultaneously-announced Sony compact primes feature similar aperture openings with the 24mm option slightly darker at f/2.8 vs. f/2.5. An f/2.5 max aperture is relatively wide. At review time, no Sony zoom lenses have a wider aperture at 40mm, though some reach f/2.8. Kit zoom lenses typically have considerably narrower apertures at 40mm. Few normal/standard prime lenses have a narrower max aperture (and most of these are macro or tilt-shift lenses). So, this lens opens wide relative to zoom lenses and not wide relative to prime lenses.

Use a wider aperture to stop action in less light and enable handholding in similarly lower light levels. Increasing the amount of light reaching the imaging sensor improves low light AF performance. In addition to allowing more light to reach the sensor, permitting faster shutter speeds or lower ISO settings, increasing the aperture opening permits a stronger subject-isolating background blur at this focal length. Wide-normal focal length lenses can blur the background reasonably well, though far behind what a telephoto lens can produce.

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The f/2.8 example above illustrates the maximum blur this lens can create. Here is another look.

Narrow aperture advantages are typically related to reduced lens element size that permits smaller overall lens size, lighter weight, and lower cost. We all can appreciate those factors, and this lens was designed for those advantages. The f/2.5 max aperture is part of the formula required for the ultra-light weight and tiny size of this lens.

When recording video, only 1/60 second shutter speeds (twice the framerate) are typically needed (assuming you're not capturing high framerate slow-motion video), and wide apertures are not often required for 1/60 second rates in normally encountered ambient lighting.

As usual for Sony FE GM and G prime lenses, the FE 40mm f/2.5 G Lens features an aperture ring, permitting a manually chosen aperture to be selected. With the ring in the A (Auto) position, the camera controls the aperture setting. All other settings electronically force the aperture to the chosen opening. A 2-position switch on the bottom right side of the lens toggles the aperture ring between 1/3 stop clicks and smooth, quiet, non-clicked adjustments, ideal for video recording. Note that this switch's orientation is rotated 90° from Sony's full-size lens design, better-utilizing the limited space.

Aside from a slightly more complicated design, I find inadvertent aperture changes the primary disadvantage of an aperture ring (especially when photographing in the dark). Incorporating a lock for this ring would eliminate that issue, and learning not to grasp the aperture ring when mounting to the camera reduces the issue.

Image Stabilization

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Sony has been omitting image stabilization, OSS (Optical SteadyShot) in their recent wide-aperture prime lenses, and not surprising is that this little lens also lacks OSS. Addressing that omission is Sony's Steady Shot IBIS (In-Body Image Stabilization) featured in their Alpha mirrorless cameras. In addition to reducing camera shake, the stabilized imaging sensor provides a still viewfinder image, enabling careful composition. Sensor-based AF takes advantage of the stabilized view for improved accuracy.

With no IS switch on the lens, the camera menu must be used to enable or disable IBIS, a slight impediment to working quickly, going from tripod to handholding, for example.

Image Quality

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We all care about image quality, and image sharpness is at the top of most of our requirements lists. Sony's MTF charts set the initial expectation, and I liked the expectations the charts for the three compact prime lenses promise.

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MTF (Modulation Transfer Function) describes how well a lens can reproduce fine details, measured as the degree of contrast achieved between finely spaced lines.
[1] Contrast (%) [2] Distance from optical center of lens (mm)
[3] Max. aperture [4] F8 aperture [5] Spatial frequency
[6] 10 lines pairs / mm [7] 30 line pairs / mm
[8] Radial values [9] Tangential values

As I said in the FE 24mm f/2.8 G Lens review, select your aperture for reasons other than contrast and resolution because this lens is sharp wide open at f/2.5. In the center of the frame, little sharpness improvement is realized by using a narrower aperture.

In general, lenses are not as sharp in the periphery, where light rays are refracted to a stronger angle than in the center. While this lens's corner performance is not quite as impressive as the center of the frame performance, the extreme image corners are rendered remarkably sharp at f/2.5. The improvements realized by stopping down are primarily related to reduced peripheral shading.

Taking the testing outdoors, we next look at a series of center-of-the-frame 100% resolution crop examples. These images were captured in RAW format using a Sony Alpha a1 and processed in Capture One using the Natural Clarity method with the sharpening amount set to only "30" on a 0-1000 scale. Note that images from most cameras require some level of sharpening, but too-high sharpness settings are destructive to image details and hide the deficiencies of a lens.

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These results are outstanding.

If present, focus shift, the plane of sharp focus moving forward or backward as the aperture is narrowed (residual spherical aberration or RSA), is often made apparent in such a comparison. Many modern lenses automatically correct for focus shift by adjusting the focus distance (this is made visible by focus breathing in aperture brackets), and a focus shift issue is not exhibited by this lens.

Next, we'll look at a comparison showing 100% corner crops captured and processed identically to the above center-of-the-frame images. The lens was manually focused in the corner of the frame to capture these images. The first row of examples is from the top right of the frame, and the next two rows are from the top left.

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Samples taken from the outer extreme of the image circle, full-frame corners, can be counted on to show a lens's weakest performance, but these examples again show the excellent performance delivered by this lens. Unlike with the FE 24mm f/2.8 G, this lens's geometric distortion does not require correction for all uses.

Corner sharpness does not always matter, but it does matter for many disciplines, including landscape photography. This lens is landscape-ready.

When used on a camera that utilizes a lens's entire image circle, peripheral shading can be expected at the widest aperture settings. This lens shows nearly three stops of shading in the corners at f/2.5, an often noticeable amount, but not an extreme amount. Peripheral shading slowly decreases as the aperture narrows, with just under two stops showing at f/4, and about one and a half stops at f/5.6. At f/8, just over a stop of shading remains, and stopping down produces no additional benefit.

APS-C format cameras using lenses projecting a full-frame-sized image circle avoid most vignetting problems. In this case, the just under one stop of shading showing at f/2.5 may be visible in some images, especially those with a solid color (such as a blue sky) showing in the corners.

One-stop of shading is often used as the visibility number, though subject details provide a widely varying amount of vignetting discernibility. Vignetting is correctable during post-processing with increased noise in the brightened areas being the penalty, or it can be embraced, using the effect to draw the viewer's eye to the center of the frame. Study the pattern showing in our vignetting test tool to determine how your images will be affected.

Lateral (or transverse) CA (Chromatic Aberration) refers to colors of the spectrum being magnified differently. Lateral CA shows as color fringing along lines of strong contrast running tangential (meridional, right angles to radii) with the mid and especially the periphery of the image circle showing the most significant amount as this is where the most significant difference in the magnification of wavelengths typically exists.

With the right lens profile and software, lateral CA is often easily correctable (often in the camera) by radially shifting the colors to coincide. However, it is always better to avoid this aberration in the first place.

Color misalignment can easily be seen in the site's image quality tool, but let's also look at a worst-case example. The image below is a 100% crop from the extreme top left corner of a Sony a1 frame showing diagonal black and white lines.

There should only be black and white colors in these images, with any additional colors indicating lateral CA. While I can see some slight corner separation, this performance is good.

A relatively common lens aberration is axial (longitudinal, bokeh) CA, which causes non-coinciding focal planes of the various wavelengths of light. More simply, different colors of light are focused to different depths. Spherical aberration along with spherochromatism, or a change in the amount of spherical aberration with respect to color (looks quite similar to axial chromatic aberration but is hazier) are other common lens aberrations to observe. Axial CA remains somewhat persistent when stopping down, with the color misalignment effect increasing with defocusing. The spherical aberration color halo shows little size change as the lens is defocused, and stopping down one to two stops generally removes this aberration.

In the real world, lens defects do not exist in isolation, with spherical aberration and spherochromatism generally found, at least to some degree, along with axial CA. These combine to create a less sharp, hazy-appearing image quality at the widest apertures.

The examples below look at the defocused specular highlights' fringing colors in the foreground vs. the background. The lens has introduced any fringing color differences from the neutrally-colored subjects.

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At the f/2.5 end of the aperture range, the color separation is relatively strong, and by f/8, the separation is mostly gone.

Bright light reflecting off of lens elements' surfaces may cause flare and ghosting, resulting in reduced contrast and sometimes interesting, usually destructive visual artifacts. The shape, intensity, and position of the flare in an image are variable, dependant on the position and nature of the light source (or sources), selected aperture, shape of the aperture blades, and quantity and quality of the lens elements and their coatings. Aided especially by the low 9-element count, this lens produced practically no flare effects even at narrow apertures in our standard sun in the corner of the frame flare test, reflecting excellent performance.

Flare effects can be embraced or avoided, or removal can be attempted. Removal is sometimes challenging. High flare resistance is a welcomed trait of this lens.

Two lens aberrations are particularly evident when shooting images of stars, mainly because bright points of light against a dark background make them easier to see. Coma occurs when light rays from a point of light spread out from that point instead of being refocused as a point on the sensor. Coma is absent in the center of the frame, gets worse toward the edges/corners, and generally appears as a comet-like or triangular tail of light which can be oriented either away from the center of the frame (external coma) or toward the center of the frame (internal coma). Coma clears as the aperture is narrowed. Astigmatism is seen as points of light spreading into a line, either sagittal (radiating from the center of the image) or meridional (tangential, perpendicular to sagittal). Remember that Lateral CA is another aberration apparent in the corners.

The image below is a 100% crop taken from the top-left corner of an a1 frame.

While this example shows the FE 40 G's image quality to not be amazing in the corner, it is not bad from a relative standpoint.

Overall, this lens shows a relatively low amount of geometric distortion — a slight amount of barrel distortion. However, the extreme full frame corners appear tucked in slightly, showing stronger barrel distortion in this area. Note that the camera will correct for this distortion regardless of the lens aberration correction setting.

Most modern lenses have lens correction profiles available (including in-camera), and distortion can easily be removed using these. Still, geometric distortion correction requires stretching which is detrimental to image quality.

As seen earlier in the review, the amount of blur a lens can produce is easy to illustrate. Assessing the bokeh quality is more challenging due to the infinite number of variables present among all available scenes. Here are some f/8 (for diaphragm blade interaction) examples.

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The first example is a 100% crop showing defocused highlights. These are relatively smoothly filled, though the shape is more polygonal vs. circular. The other example is a full image reduced in size and looking nice.

Except for a small number of specialty lenses, the wide aperture bokeh in the frame's corner does not produce round defocused highlights, with these effects taking on a cat's eye shape due to a form of mechanical vignetting. If you look through a tube at an angle, similar to the light reaching the frame's corner, the shape is not round, and that is the shape seen here.

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From a relative standpoint, these results appear nice. As the aperture narrows, the entrance pupil size is reduced, and the mechanical vignetting absolves with the shapes becoming rounder.

With a 7-blade count diaphragm, point light sources captured with a narrow aperture setting and showing a sunstar effect will have 14 points. In general, the more a lens is stopped down, the larger and better-shaped the sunstars tend to be. Wide aperture lenses tend to have an advantage in this regard, and this lens is capable of producing beautiful stars.

The example above was captured at f/16.

The design of this lens is illustrated below in a comparison featuring the sibling compact primes.

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[1] Aspherical lens [2] ED (extra-low dispersion) glass

"Impeccable Sony G Lens design emphasizes a graceful balance between high resolution and gorgeous background bokeh that can enhance the artist’s vision." [Sony]

A strong Sony FE 40mm f/2.5 G Lens selling point is the image quality it produces. Aside from the distortion in the corners and the wide aperture color fringing, this lens leaves little to desire.

Focusing

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"Two linear motors deliver fast, precise AF with superb tracking performance that maximizes camera body performance to capture vital moments in street snaps and the like. The fast, precise and quiet AF with superb tracking performance is ideal for shooting movies as well as stills." [Sony]

While Sony is not promoting the use of the "XD" version of their linear motors, this lens has small elements to move. The Sony FE 24mm f/2.8 G Lens focuses internally, essentially silently, and with good speed.

The AF accuracy from this lens has been excellent (like the rest of the FE lenses), and low light AF performance from this f/2.8 lens is also excellent.

Normal is for the scene to change size in the frame as the focus is pulled from one extent to the other, referred to as focus breathing, a change in focal length resulting from a change in focus distance. Focus breathing negatively impacts photographers intending to use focus stacking techniques, videographers pulling focus, and anyone critically framing while adjusting focus. This lens produces a moderate change in subject size through full extent focus distance adjustment.

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Despite the tiny size of this lens, a customizable AFL button is provided. While in continuous focus mode, this button can be pressed to lock focus at the currently selected focus distance, permitting a focus and recompose technique, perhaps to grab a quick pano. This button also acts as a custom button and can be programmed to another function using the camera's menu.

FTM (Full Time Manual) focusing is supported via Sony's DMF (Direct Manual Focus) AF mode.

This lens has an AF/MF switch, allowing this frequently used camera setting to be changed without using the menu system. Different is that this switch is rotated 90° of the usual orientation, better-utilizing space on the small lens barrel.

The all-metal exterior construction of this lens extends to the focus ring. The gear-like focus ring is easy to grasp, including by follow focus rigs. However, the small size of this lens, along with the other included features, permits only a slim focus ring size. In addition to its small size, the focus ring is positioned close to the similarly ribbed aperture ring, adding slight complication to finding the focus ring. Find the end of the lens or back of the lens hood to find this focus ring tactilely.

Electronic focusing (vs. gear driven) AF can enable a variable rate of focus adjustment based on the focus ring rotation speed. However, this feature must be properly tuned to avoid frustration when rocking the ring back and forth to obtain a precise focus setting, and the variable rate can be problematic when pulling focus during video capture. Those issues do not apply to this lens, featuring a linear focusing system, my preference.

This ring is smooth, has an ideal amount of resistance, and the 155° of MF rotation linearly adjusts focusing at an ideal rate, allowing precise manual focusing even at close distances.

Manual focusing provides a minimum focus distance of 9.8" (250mm), with a respectable 0.23x maximum magnification. If using AF, this lens's minimum focus distance increases slightly to 11.0" (280mm), with the maximum magnification spec dropping to a still reasonable 0.20x.

Model	Min Focus Distance "(mm)		Max Magnification
Sigma 35mm f/2 DG DN Contemporary Lens	10.6	(270)	0.18x
Sony FE 24mm f/2.8 G Lens	7.1	(180)	0.19x
Sony FE 35mm f/1.8 Lens	8.7	(220)	0.24x
Sony FE 35mm f/2.8 ZA Lens	13.8	(350)	0.12x
Sony FE 40mm f/2.5 G Lens	9.8	(250)	0.23x
Sony FE 50mm f/2.5 G Lens	12.2	(310)	0.21x
Tamron 35mm f/2.8 Di III OSD Lens	5.9	(149)	0.50x

A subject measuring approximately 6.3 x 4.2" (160 x 107mm) fills a full-frame imaging sensor at this lens's minimum focus distance (MF). The evening primroses below were photographed at the minimum focus distance.

Close distance image quality remains nice.

Need a shorter minimum focus distance and higher magnification? An extension tube mounted behind this lens should provide a significant decrease and increase, respectively. Extension tubes are hollow lens barrels that shift a lens farther from the camera, allowing shorter focusing distances at the expense of long-distance focusing. Electronic connections in extension tubes permit the lens and camera to communicate and otherwise function as normal. As of review time, Sony does not publish extension tube specs, nor do they manufacture these items, but third-party Sony compatible extension tubes are available.

This lens is not compatible with Sony teleconverters.

Build Quality & Features

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"The metal (aluminum) exterior finish of the lens body and hood contributes to reliability through increased strength and durability." [Sony]

The little Sony FE 24mm f/2.8 G Lens's design is unlike any FE lenses before it. The appearance, including etched letters and numbers, is classy. The all-metal construction coupled with this design provides a high-grade feel.

Here is a closer look at the 40mm f/2.5 G lens.

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With a focus ring, aperture ring, click switch, AF/MF switch, and AF stop button, this small lens barrel has a lot going on. However, these controls are useful, and I especially appreciate the AF/MF switch remaining present. With the cameras able to perform that function, this AF/MF switch becomes an omit-able feature.

This lens features dust and moisture resistance, including a slim mount gasket.

There are few lenses smaller or lighter than this one. This lens can easily be carried all day, and it consumes little space in the case. Notice the size and nearly identical weight of the trio of Sony compact prime lenses. Swap these lenses in cases or on a gimbal with little or no reconfiguration.

Model	Weight oz(g)		Dimensions w/o Hood "(mm)		Filter	Year
Sigma 35mm f/2 DG DN Contemporary Lens	11.5	(325)	2.8 x 2.7	(70.0 x 67.4)	58	2020
Sony FE 24mm f/2.8 G Lens	5.7	(162)	2.7 x 1.8	(68.0 x 45.0)	49	2021
Sony FE 35mm f/1.8 Lens	9.9	(281)	2.6 x 2.9	(65.6 x 73.0)	55	2019
Sony FE 35mm f/2.8 ZA Lens	4.2	(120)	2.4 x 1.4	(61.5 x 36.5)	49	2014
Sony FE 40mm f/2.5 G Lens	6.1	(173)	2.7 x 1.8	(68.0 x 45.0)	49	2021
Sony FE 50mm f/2.5 G Lens	6.1	(174)	2.7 x 1.8	(68.0 x 45.0)	49	2021
Tamron 35mm f/2.8 Di III OSD Lens	7.4	(210)	2.9 x 2.5	(73.0 x 63.5)	67	2019

For many more comparisons, review the complete Sony FE 40mm f/2.5 G Lens Specifications using the site's lens specifications tool.

This little lens provides adequate finger clearance on the Sony Alpha a7 III, a7R III, a7 IV, and similarly designed cameras.

Here is a visual comparison:

Positioned above from left to right are the following lenses:

Sony FE 35mm f/2.8 ZA Lens
Sony FE 40mm f/2.5 G Lens
Sigma 35mm f/2 DG DN Contemporary Lens
Tamron 35mm f/2.8 Di III OSD Lens
Sony FE 35mm f/1.8 Lens

The same lenses are shown below with their hoods in place.

Use the site's product image comparison tool to visually compare the Sony FE 40mm f/2.5 G Lens to other lenses.

All three simultaneously introduced Sony compact prime lenses utilize relatively small and inexpensive 49mm filters. While this size is not especially common, seven current Sony FE lenses feature 49mm filter threads. With the three compact primes functioning especially well as a kit, their shared size is especially welcomed.

A plastic lens hood on a lens featuring an all-metal exterior would not be right, and the Sony engineers behind this lens design knew that. The Sony FE 40mm f/2.5 G Lens's round-shaped aluminum ALC-SH166 hood, shared with the 50mm G lens, is compact like the lens. This hood is compactly efficient.

Note that the FE 24 G and FE 40mm G hoods fit on both lenses — remember that 40mm lens logically gets the narrower hood.

A lens case is not included in the box, but finding somewhere to stow this lens's small footprint should not be challenging.

Price, Value, Compatibility

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The FE 40mm f/2.5 G Lens is one of the most affordable Sony FE lenses. This lens is a great value for the price with the as-expected good image and build qualities.

As an "FE" lens, the Sony FE 40mm f/2.5 G Lens is compatible with all Sony E-mount cameras, including full-frame and APS-C sensor format models. Sony provides a 1-year limited warranty.

I purchased the Sony FE 40mm f/2.5 G review lens online-retail.

Alternatives

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At review time, there are no other 40mm lenses in the Sony lineup. Sigma has a impressive 40mm lens, the Sigma 40mm f/1.4 DG HSM Art Lens, but this lens is in a different class. 40mm is close to 45mm, and the Tamron 45mm f/1.8 Di VC USD Lens is another nice option, but a mount converter is required to use it on a Sony camera.

Stepping up to 50mm or down to 35mm provides a plethora of options.

At 35mm, the Sony FE 35mm f/2.8 ZA Lens carries similar primary specifications, with the G lens having a modest max aperture advantage.

In the image quality comparison, the G lens is modestly sharper than the ZA lens. The ZA lens has stronger peripheral shading, including at narrow apertures, and less geometric distortion.

The Sony FE 40mm f/2.5 G Lens vs. Sony FE 35mm f/2.8 ZA Lens comparison shows the ZA lens remarkably weighing only about 2/3 as much as the G lens and measuring slightly less as well. The G lens features an aperture ring, has various switches, including AF/MF, and has dual vs. single linear AF motors. The G lens also nearly doubles the ZA lens's maximum magnification, 0.23x vs. 0.12x. The ZA lens has a larger focus ring and costs moderately more than the G.

Another lens in the small and light 35mm category is the Sony FE 35mm f/1.8 Lens, with this lens having a significantly wider aperture opening. In the wide-open aperture image quality comparison, the G lens takes the easy win. With the apertures equalized at f/2.8, the sharpness difference is mostly erased, with the G lens holding the peripheral advantage. The G lens has less peripheral shading. The G lens has barrel distortion, and the f/1.8 lens has pincushion distortion. When compared, the difference appears significant, but the f/1.8 lens may hold only a slight advantage in this respect.

The Sony FE 40mm f/2.5 G Lens vs. Sony FE 35mm f/1.8 Lens comparison shows the f/1.8 lens, a small and light model, weighing and measuring slightly more than the G lens. The G lens features an aperture ring and dual vs. single linear AF motors. The f/1.8 lens has 9 aperture blades vs. 7, has a larger focus ring, takes 55mm filters vs. 49mm, and costs modestly more.

Sigma has an entry in the 35mm compact prime lens class. The Sigma 35mm f/2 DG DN Contemporary Lens is a great little metal-constructed lens with image quality that should challenge the Sony G lens at comparable apertures. That the Sigma opens up to f/2 is a top-of-the-list advantage.

In the wide-open aperture image quality comparison, the Sony lens holds a center of the frame sharpness advantage. Equalize to f/2.8, and the Sony lens advantage is at least gone. The Sigma lens has slightly stronger peripheral shading at narrow apertures.

The Sony FE 40mm f/2.5 G Lens vs. Sigma 35mm f/2 DG DN Contemporary Lens comparison shows the compact Sigma lens's weight approaching 2x as much as the Sony's weight and measuring modestly longer. Figure that difference the price to be paid for the wider aperture. The Sigma lens has 55mm filter threads vs. 49mm. The Sony lens has a higher maximum magnification, 0.23x vs. 0.18x. The Sigma lens has a slightly higher price.

One lens in Tamron's matched set of compact prime lenses has a 35mm focal length, and the Tamron 35mm f/2.8 Di III OSD Lens is a good performer, turning in sharp images at f/2.8. The wide-open aperture image quality comparison shows the Sony lens delivering sharper results. At f/4, the results from these lenses appear nearly equal.

The Sony FE 40mm f/2.5 G Lens vs. Tamron 35mm f/2.8 Di III OSD Lens comparison shows the Tamron lens weighing a tiny amount more and measuring modestly larger. The Tamron compact prime trio uses 67mm filters vs. 49mm, and the Tamron lens's 0.50x maximum magnification far surpasses the Sony lens's 0.23x figure. The Sony lens offers a variety of switches, including for AF/MF, along with a manual aperture ring, and has a modestly wider aperture. A key factor is that the Tamron lens is much less expensive.

The other two Sony compact prime lenses, the FE 40mm f/2.5 G and FE 50mm f/2.5 G could be compared here. However, these lenses are basically equals aside from their focal length, and that is the factor that should be used in the decision between these three lenses. These lenses are complementary, with the longer two lenses offering a slightly wider aperture and a slightly higher maximum magnification.

What about a zoom lens for comparison? The Sony FE 24-70mm f/2.8 GM Lens offers the 40mm f/2.8 focal length and aperture combination along with the versatility of a long-range of focal lengths.

In the image quality comparison (40mm vs. 35mm), the prime lens shows a primary reason why you might opt for a prime lens over a zoom lens — sharper imagery. The zoom lens has less distortion (at 35mm) and less peripheral shading at f/2.8.

The Sony FE 40mm f/2.5 G Lens vs. Sony FE 24-70mm f/2.8 GM Lens comparison shows another dramatic difference between these lenses: size and weight. Add the filter size to those differences — 49mm is far smaller than 82mm. The three compact G primes combine to weigh only 2/3 of the zoom lens's weight. The in-the-hand weight difference between one prime and the zoom lens is huge, especially after a long period of use. Of course, if the shot is missed because the right focal length was not mounted, all the prime lens advantages are gone.

The zoom lens has two additional aperture blades, 9 vs. 7. The prime lens has a 1/3-stop wider aperture available. If the zoom lens is on sale, the three prime lenses combine to match the zoom lens price.

Use the site's comparison tools to create additional comparisons.

Summary

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As I said at the beginning of this review, the Sony FE 40mm f/2.5 G lens is a highly attractive, ultra-compact prime lens that features an extremely light weight and a rugged metal exterior construction. The 40mm focal length is useful, and the f/2.5 aperture is ready to tackle the low light venues and create a nicely blurred background. That this is one of the most affordable Sony FE lenses will aid its popularity.

Image quality-related downsides are strong color fringing at wide apertures and relatively strong barrel distortion in the corners of the frame. Especially for the size, weight, and price, the image quality this lens produces is excellent.

Create a kit of the three simultaneously announced compact prime lenses for convenient coverage of a wide range of needs.