I used the Sony FE 40mm F2.5 G on the Sony A7R IV, which, with 61-million effective pixels, is the highest resolution full-frame camera currently available. That means that the lens’s resolving power had every chance to show itself, and I’m very impressed by the amount of sharp detail visible at the centre of its images.
Even at maximum aperture, f/2.5, there’s a very high level of sharpness and nice micro contrast. However, closing to f/2.8 ups the game slightly and at f/4 and f/5.6, the sharpness is stunning – it’s hard to imagine that there can be more detail in an image.
When images are sized to fill a 27-inch screen, there’s a slight fall-off in sharpness apparent at f/2.5 but it’s not problematic. Closing to f/2.8 improves the situation and by f/4 the fine details are crystal-clear.
Sharpness levels stay very high up to around f/11 and beyond, but by f/16 there’s a suggestion of the impact of diffraction and if you examine images at 100%, you’ll see the corners soften again fractionally. Diffraction means that the results at f/22 suffer in comparison with those captured at mid-range apertures. They’re not bad, but it’s worth sticking to f/16 or wider if you can.
Out of focus areas generally look good from the Sony FE 40mm F2.5 G, they’re pleasantly smooth and rounded. However, scrutinising the ‘bokeh balls’ created by pinpoint highlights reveals that some have a hint of bokeh chromatic aberration and concentric circles (onion skin effect) within. Also, the highlights towards the edges of the frame take on a ‘cat’s eye’ shape.
If the in-camera or post-capture correction profiles aren’t applied, very slight barrel distortion is visible in images with lots of straight lines. There’s also a little vignetting at f/2.5, but it’s well within an acceptable range and using the correction profile or closing to f/4 eliminates it if you find it troublesome.
Even with the correction profiles applied, I found a few examples of chromatic aberration causing purple fringing along backlit edges. However, it’s not a major problem and it’s dealt with in a matter of seconds using Adobe Camera Raw’s ‘Defringe’ tool.
Sony supplies a conical or inverted type lens hood with the FE 40mm F/2.5 G and this does a great job of keeping flare at bay. If the hood if removed and the lens is angled so light skims across its surface or the sun is towards the edge of the frame you can force the issue and introduce a little flare, but that’s inevitable and its controlled well.
As you’d expect, the Sony FE 40mm F2.5 G is fully compatible with Sony’s latest autofocus systems, including Eye AF. It gets subjects sharp very quickly and silently. However, adjusting the focus from the closest focus point to the furthest, or vice-versa results in a change in the framing, which could be an issue for some videographers or photographers looking to focus stack.