Hands-on with Sony's compact G primes
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Sony recently announced a set of three compact full-frame E-mount prime lenses: the 35mm F2.8G, the 40mm F2.5G, and the 50mm F2.5G. 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.
Size and weight
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All three lenses measure 64mm (2.5") in diameter and 45mm (1.8") in length. The 24mm F2.8G weighs 162g (5.8oz), the 40mm F2.5G weighs 173g (6.2oz), and the 50mm F2.5G weighs just a gram more at 174g. All three lenses have 49mm front filter threads.
These lenses compare favorably in terms of size and weight next to their most obvious competitors. For example, the Tamron 35mm F2.8 lens is 37g – or 18% – heavier than the FE 40mm F2.5G, and 19mm, or 42%, longer too.
Build quality and sealing
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All three lenses are described as being dust and moisture resistant, and have rubber gaskets around their respective lens mounts to help protect against moisture and other contaminants entering the camera body. Additional seals are indicated for the 24mm F2.8G lens in orange above (here are similar diagrams for the 40mm and 50mm lenses).
Build quality and sealing
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Both the lens bodies and hoods have a metal (aluminum) exterior finish for increased strength and durability. Speaking of the lens hoods, all lenses come with bayonet-style ones. The 40mm and 50mm hoods additionally offer front 49mm filter threads of their own, as their design makes it difficult to mount filters on the lens itself.
External controls
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Despite the compact size, all three G primes offer a good degree of manual control. On all three models, an AF/MF switch offers quick control over focus mode, and a focus hold button right above it can be customized to any assignable function. The focus ring, located at the front of the lens barrel on each lens, offers linear focus response for intuitive focus pulling in stills and video.
External controls
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A physical aperture ring with 1/3 EV detents offers quick control over f-stop on each of Sony's new primes. They can be clicked or 'de-clicked', with the latter option allowing for smooth depth-of-field changes when shooting video.
Optical design
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The 24mm F2.8G lens is optically comprised of 8 elements in 7 groups, while the 40mm and 50mm F2.5 primes are comprised of 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.
MTF - 24mm F2.8G
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All three new lenses offer very high contrast across the frame wide open (left graph), indicated by the orange traces hugging the 100% (or, perfect) line for much of the frame. The 24mm is probably the standout here though, as it never dips below 90%. Stopped down (right graph) contrast is nearly perfect, but we've come to expect this of most lenses.
The 24mm is also the standout of the three lenses when it comes to center sharpness, which is at or near 95% wide open. Although the MTF curves indicate the lens sharpens up as you stop down - right up to 100% at center by F8 (right graph) - it's fairly difficult to tell in real world shooting due to how sharp the lens is at F2.8. In our aperture progression included in our sample gallery, there's a very slight increase in central sharpness going from F2.8 to F4, but by the time you reach F8 on a 60MP sensor, there's some softening due to diffraction.
While the MTF curves indicate the lens sharpens up peripherally upon stopping down, the increase in sharpness is fairly subtle (from ~70% to 80% at the edges), and visually rather difficult to discern. A likely reason for why stopping down doesn't improve resolution more significantly at the corners is the rather extreme amount of stretching that occurs at the edges to correct the high levels of distortion left behind in the optical design.
A note on reading these graphs: sagittal or radial traces are solid while tangential traces are dotted. Orange traces are for 10 lp/mm detail, often indicative of lens' contrast performance. Green traces are for 30 lp/mm detail, often indicative of lens' sharpness performance. The horizontal axis ranging from 0 - 24 at the bottom of each graph represents radial distance (mm) from the optical center of the lens, while the vertical axis represents % contrast. The higher the traces, the better.
MTF - 40mm F2.5G
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The 40mm F2.5G also exhibits outstanding contrast (orange) across the frame wide open (left graph), which improves to essentially perfect performance upon stopping down (right graph). Sharpness (green) is also very high centrally and for much of the frame - though not as high as the 24mm prime - hovering around 85 - 90% for much of the imaging circle. Like the 24mm F2.8G, sharpness drops as you reach the peripheries of the image, and improve more significantly upon stopping down to F8. In fact, by F8, contrast and sharpness across the frame is outstanding, essentially at 90% or higher for both figures across the entire frame.
The 40mm prime requires less digital distortion correction than the 24mm, albeit significantly more than the 50mm, so we're not surprised to see more of an increase in edge sharpness upon stopping down.
A note on reading these graphs: sagittal or radial traces are solid while tangential traces are dotted. Orange traces are for 10 lp/mm detail, often indicative of lens' contrast performance. Green traces are for 30 lp/mm detail, often indicative of lens' sharpness performance. The horizontal axis ranging from 0 - 24 at the bottom of each graph represents radial distance (mm) from the optical center of the lens, while the vertical axis represents % contrast. The higher the traces, the better.
MTF - 50mm F2.5G
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From a contrast and sharpness perspective, the 50mm F2.5G behaves very similarly to the 40mm F2.5G. Contrast is essentially perfect centrally wide open (left graph), and only fractionally less so at the corners, reaching perfect performance upon stopping down to F8 (right graph). Central sharpness is at 90% or better for the first 10mm of the imaging circle, only dipping below an average (or the radial and tangential traces) of 70% well out at the image peripheries. Stopping down to F8 yields outstanding performance, with ~90 - 98% contrast across the entire frame.
The 50mm lens requires little to no digital distortion correction, so the significant improvement in edge and corner sharpness upon stopping down isn't surprising.
A note on reading these graphs: sagittal or radial traces are solid while tangential traces are dotted. Orange traces are for 10 lp/mm detail, often indicative of lens' contrast performance. Green traces are for 30 lp/mm detail, often indicative of lens' sharpness performance. The horizontal axis ranging from 0 - 24 at the bottom of each graph represents radial distance (mm) from the optical center of the lens, while the vertical axis represents % contrast. The higher the traces, the better.
Auto / manual focus
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The all-internal focus groups are driven by dual linear motors for nearly instantaneous autofocus: we measure less than 0.5s to rack focus from infinity to minimum focus distance. It's difficult for us to measure speeds faster than 0.5s, but we suspect actual focus speed to be faster. Lenstip measures 0.3-0.4s for the 24mm, and 0.4-0.5s for the 40mm. Focus is silent, as well.
Minimum focus distances range from 0.18m (7.1") for the 24mm to 0.25m (9.8") for the 40mm to 0.31m (12.2") for the 50mm. These numbers increase slightly to 0.24m, 0.28m and 0.35m, respectively, when using autofocus. That works out to pretty respectable magnification ratios of 0.19x, 0.23x and 0.21x for the 24mm, 40mm, and 50mm lenses, which increase slightly to 0.13x, 0.2x and 0.18x when autofocus is engaged.
Pricing and availability
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The Sony FE 24mm F2.8, 40mm F2.5 and 50mm F2.5 trio will be available in mid-to-late May for $599 each.
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