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Tested: Sony’s trio of compact 24mm, 40mm and 50mm G prime lenses: Digital Photography Review

Earlier this year Sony announced a set of three compact full-frame E-mount prime lenses: the 24mm F2.8 G, the 40mm F2.5 G, and the 50mm F2.5 G. Their small, lightweight design makes them convenient for casual and on-the-move photographers, and their nearly identical sizes and weights make them ideal for gimbal movie shooters requiring the versatility of a few different focal lengths. All three lenses weigh roughly 170g, offer 49mm filter threads and come in at an MSRP of $599 USD.

We wanted to take a look at how they perform optically. But first, let’s start with the optical designs:

Optical designs of the 24, 40, and 50mm compact G primes from Sony

We’ve previously pored over and extrapolated as much as we could from the (theoretical) MTF figures of each of these primes: the 24mm, the 40mm, and the 50mm. Now that we’ve had them in our hands, we can take a closer look at how they perform in real-world usage.The Sony 24mm F2.8 G prime comprises 8 elements in 7 groups, while the 40mm and 50mm F2.5 G primes comprise 9 elements in 9 groups. All three of Sony’s latest G-series primes use aspherical elements (indicated in purple above) to maintain high resolving power across the frame and reduce common aberrations, according to Sony. The 24mm and 50mm lenses additionally employ one ED (extra-low dispersion) element each in their respective designs to reduce chromatic aberrations and fringing.

Sharpness and Lateral CA

One thing is clear up front: these lenses are already at their peak sharpness practically when shot wide open. So if you’re shooting in low light or trying to isolate your subject, you can shoot wide open without any worry of sacrificing sharpness. Below we examine lens performance for an infinity scene. All images have had distortion correction applied; however, lateral chromatic aberration and vignetting remain uncorrected.

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Sony 24mm F2.8 G

In the center, the 24mm F2.8 G is very sharp wide open, with little-to-no evidence of any ‘veiled soft’ look at wide apertures, thanks to nearly 100% MTF response for low contrast detail wide open. There’s only the tiniest increase in sharpness going from F2.8 to F4 in the center, and it’s hard to discern even in side-by-side A/B comparisons. The lens is sharp enough that you might notice a slight diffraction-induced softening going from 5.6 to F8 on a high-resolution sensor such as the a7R IV.

At the edges, you don’t really see an increase in sharpness until you get to F8, and it’s minimal at best, something confirmed from its theoretical MTF traces. There doesn’t seem to be much field curvature, as focusing out toward the edges doesn’t really help sharpen things up. Focusing at the edges does decrease center sharpness ever so slightly, though, so if you’re shooting a distant flat scene, you’re better off simply focusing at the center.

The 24mm F2.8 G has some lateral chromatic aberration that gets slightly worse as you stop down, but it’s easily removed automatically in JPEGs or in post-processing with the metadata embedded in the Raw file. The lens remains tack sharp at close-focus distances, too, and has a respectable maximum magnification of 0.19x in manual focus mode (0.13x with AF).

Sony 40mm F2.5 G

The 40mm F2.5 G is extremely sharp wide open, again with no dreamy softness thanks to a nearly 100% MTF response for low contrast detail wide open. While the sharpness MTF traces (30 lp/mm) increase noticeably upon stopping down, it’s so modest that it’s barely visible even in real-world side-by-side comparisons. Beyond F2.8, it’s difficult to note any increase in sharpness, which is a testament to its performance.

The lens is so sharp that it’s fairly easy to spot diffraction-induced softening by F8. Corner sharpness increases once you get to F5.6, but the increase in sharpness is fairly modest since the edges are pretty sharp to begin with wide open. There’s no increase in edge sharpness if you focus at the edge (as opposed to the center), suggesting very well-controlled field curvature that is low enough for you to not concern yourself with it.

The 40mm F2.5 G has no discernible lateral chromatic aberration. Close-up performance remains quite good wide open, with sharp results and little loss of contrast. The lens can focus down to 0.25m in manual focus mode, yielding 0.23x maximum magnification (0.2x with AF).

Sony 50mm F2.5 G

At the risk of sounding like a broken record, the 50mm F2.5 G is extremely sharp wide open, with no veiled look wide open thanks to nearly perfect contrast wide open. Like the 40mm F2.5 G, it gets a smidgen sharper going from F2.5 to F2.8 (predicted by the 30 lp/mm sharpness MTF plots), but it’s difficult to perceive any increase in sharpness as you stop down further from F2.8. A lens that’s diffraction limited by F2.8 to F4 is an incredibly sharp lens indeed, so kudos to Sony’s designers; this series of primes seem optimized for sharpness at or very near wide open.

You’ll start to see diffraction-induced softening by F8 and definitely by F11. Edges sharpen up slightly at F5.6 and more so at F8, but it’s a modest improvement over the already sharp results wide open. There’s no increase in corner sharpness if you focus out there; in fact, a decrease if anything. This indicates the lens likely has a very flat field of focus, an attribute it shares with the 24mm and 40mm primes.

Lateral chromatic aberration is extremely well-controlled: we can’t see even a hint of it at 1:1 magnification. Images shot at close-focusing distances remain sharp wide open, with a close focus distance of 0.31m and a maximum magnification of 0.21x in manual focus mode (0.18x with AF).

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All three lenses vignette significantly when shot wide open, which isn’t too surprising given their compact sizes.

The 24mm F2.8 G has significant vignetting wide open, and continues to vignette until F11 where it is barely noticeable. Yet there is still a small decrease in vignetting going from F11 to F16. At its worst, at F2.8, we measure the vignetting to be 1 stop at the corners relative to F16.

The 40mm F2.5 G fares a bit better in the vignetting department, with most of the vignetting clearing up by F5.6. However, F8 still shows less vignetting in the corners than F5.6, and there’s a slight increase in brightness in the extreme corners even at F11. At F2.5 we measure a 1.2 EV drop in corner brightness relative to F16.

It’s a similar story with the 50mm F2.5 G: most of the vignetting clears up by F5.6, but the corners brighten up a bit more at F8, while the extreme corners don’t reach their peak brightness until F11. At F2.5 we measure a 1.1 EV drop in corner brightness relative to F16.

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We don’t worry too much about distortion these days simply because of how easily corrected it is in JPEGs or during the Raw conversion process, but it’s insightful to look at in understanding why some edge softness may never sharpen up even upon stopping the lens down.

24mm F2.8 G

The 24mm F2.8 G exhibits a high degree of barrel distortion. While it’s easily corrected for, the stretching of the edges of the image upon correction may account for some of the edge softness that persists even up on stopping the lens down.

Slide the circle with the arrow carrots right to view the corrected image, and left to view the uncorrected image, below.

40mm F2.5 G

The 40mm F2.5 G lens also shows some barrel distortion, but it’s far less severe than the 24mm F2.8 G. It’s not too surprising, then, that edge sharpness does increase upon stopping the lens down, as there isn’t a lot of stretching occurring at image edges upon correction of distortion.

50mm F2.5 G

The 50mm F2.5 G lens shows very little distortion; in fact the corrected and uncorrected images appear nearly identical. The low level of distortion means that edges and corners of the image aren’t stretched at all after distortion correction, and so these areas of the image remain quite sharp especially upon stopping the lens down.

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Bokeh characteristics vary across the three primes. All three lenses exhibit some cats eye effect out towards the image edges, and while the effect isn’t too distracting, it’s a bit more than we might expect for lenses with such moderate maximum apertures. Have a look at cats eye effect by following these links for the 24mm, 40mm, and 50mm lenses.

Taking a closer look, the 24mm F2.8 G has the smoothest bokeh discs (or circle-of-confusion/CoC) of the pack, with little to no apparent texture or onion rings. However, it exhibits a bit of ‘soap bubble’ effect, visible as bright edges around the CoC. Although this can lead to a slightly busy appearance where bokeh discs start to overlap, we didn’t find it too much of an issue in real-world usage. Stopping the lens down to F4, however, leads to a polygonal-shaped CoC, as the 7-bladed aperture has too few blades to retain a circular shape.

The 40mm and 50mm F2.5 G lenses have similar bokeh characteristics: both lenses exhibit texture and onion ring patterning to their CoCs. We should mention, though, that we’ve only tested one copy of each lens, and it’s possible that other units of these lenses may have more or less texture in out-of-focus specular highlights. However, in our years of testing we have noted that lenses with small elements and longer focal lengths are more prone to textured CoCs, due to small defects in element surfaces presenting over a greater proportion of the image- compared to similar sized defects in lenses with larger elements. Hence we do expect the the 24mm F2.8 G to yield smoother out-of-focus bokeh discs relative to the 40mm and 50mm lenses.

Wide open there’s not much of an issue at all with bright edges to the CoC, but stop the lenses down to F4 and you’ll notice a similar bright edge to the CoC as with the 24mm F2.8 G. Again, we didn’t find this to negatively impact bokeh significantly in real-world usage (follow the gallery links at the bottom of the page to judge for yourself).

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Longitudinal CA / Bokeh Fringing

While the 40mm and 50mm F2.5 G lenses show no observable lateral chromatic aberration (LCA), the 24mm F2.8 G does. Funnily enough, the situation is precisely reversed when it comes to longitudinal chromatic aberration (LoCA)! Both the 40mm and 50mm F2.5 G exhibit a fair degree of LoCA, visible as purple and green fringing in front of, and behind, the focus plane, respectively. Meanwhile, LoCA is quite well controlled on the 24mm F2.8 G.

Longitudinal chromatic aberration (LoCA) of the 24mm F2.8 G (left), 40mm F2.5 G (center), and 50mm 2.5G (right) lenses. The 40mm and 50mm F2.5 G lenses exhibit a significant amount of LoCA, visible as green fringes around out-of-focus highlights behind the focus plane. The 24mm F2.8 G controls this type of CA fairly well.

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Flare / Ghosting

If you point the lenses directly at the sun or similar bright light sources, you may notice some loss of contrast due to flare, particularly when shooting wide open and more so with the 40mm and 50mm F2.5 G lenses. The 24mm F2.8 G fares a bit better in this regard, but it’s not entirely immune to contrast-reducing flare. The good news is that for each lens, the contrast loss is fairly minimal. All three lenses show a fair degree of ghosting, caused by repeated reflections off of internal lens surfaces. When the reflections occur in front of or behind the lens aperture, the ‘ghosts’ take on the shape of the aperture. Compare all three lenses shot into the sun wide open below.

Stopping the lenses down to F16, the ghosts becomes more apparent and better defined, particularly with the 40mm and 50mm F2.5 G lenses. Stopped down, the image artifact can be distracting, but keep in mind that in the scenario here we purposefully adjusted the angle and composition to maximize flare and ghosting, and it’s unlikely to be an issue in most situations.

The sunstar performance of all three lenses is quite similar. The 7-bladed apertures yield 14-ray sunstars. They’re nice, but they won’t blow you away: the rays aren’t as sharply defined as we tend to like, and we appreciate the 18 and 22-point sunstars that 9-bladed and 11-bladed apertures, respectively, yield.

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Sony’s G ‘mini primes’ are a welcome addition to the full-frame E-mount lineup. They perform well optically, focus nearly instantaneously thanks to their double linear motors, and cover useful focal lengths while featuring relatively fast apertures. Their physical similarity makes them great for video work where you may wish to swap focal lengths without having to re-configure or re-balance your gimbal or drone. That said, they’re not without their flaws.

In terms of resolving power, the sharpness of these lenses doesn’t disappoint: you can happily shoot them wide open without any worry of sacrificing much, or any perceivable, image quality. Their linear motors focus nearly instantaneously, so you can keep up with fast action. Lateral CA simply isn’t an issue for the 40mm and 50mm primes, and the relatively minor amount that’s there on the 24mm F2.8 G is easily removed in post-processing. Distortion is a bit extreme on the 24mm but easily corrected for; however, it’s possible that the need for correction negatively impacts image sharpness at the edges even at smaller apertures. It’s only extreme edges affected, though, so it’s nothing we’d be concerned about.

Sony’s G compact primes are optically well-performing, fast-focusing lenses of useful focal lengths

Bokeh is arguably a bit smoother on the 24mm F2.8 G, with the 40mm and 50mm primes suffering from textured out-of-focus highlights with onion rings and significantly magenta and green bokeh fringing. That fringing is caused by a fair bit of longitudinal CA that can impact real world images, particularly in areas of the image just falling out of focus. None of these primes are immune to flare and ghosting, which is somewhat expected for this type of lens at this price point.

If you don’t find yourself chasing the shallowest depth-of-field or needing the extra light available from F1.2 – F2 lenses, these primes are a great way to save some money and some weight and space in your camera bag. We imagine most users will choose between the 40mm and 50mm primes, and will benefit from knowing there really isn’t a significant difference in optical performance. The 24mm F2.8 G appears to be a cut above the 40 and 50mm primes optically, and we imagine it finding its way into at least a few camera bags. Meanwhile, the 50mm F2.5 G is an attractive alternative to the more expensive Sony/Zeiss 55mm F1.8, thanks to its excellent sharpness and relatively similar bokeh and longitudinal and lateral CA performance compared to that lens. The 40mm F2.5 G leaves us scratching our heads a bit: it’s not quite in between the 24mm and 50mm lenses and we have a feeling most people will opt for the excellent 35mm F1.8 lens instead.

Sample galleries

Please do not reproduce any of these images without prior permission (see our copyright page).

Sony 24mm F2.8 G gallery

Sony 40mm F2.5 G gallery

Sony 50mm F2.5 G gallery

Sony mini primes sample gallery (DPReview TV)

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