Shooting with the Sony A7R V, which has an excellent autofocus system, meant I didn’t encounter any occasions when I had to switch focusing manually. The AF system gets the subject sharp quickly and quietly. However, there are times when it’s helpful to focus manually, and the Sony FE 20-70mm F4 G’s manual focus system is very responsive to any rotation of the focus ring. As usual, the movement of the ring can trigger the area under the AF point to magnify in the viewfinder and on the main screen, which makes it easy to ensure the subject is sharp.
Further good news is that focus breathing is controlled very well for most of the focal length range, but you’re likely to spot a slight shift in the framing at the wide-angle end when the focus moves from infinity to the closest point. However, this is pretty effectively addressed, albeit with a slight crop, by activating the Focus Breathing Compensation feature found on Sony’s latest cameras, including the Sony A7 IV and A7R V.
My images shot throughout the focal length and aperture ranges reveal that the Sony FE 20-70mm F4 G delivers excellent detail resolution, even when the aperture is wide open. There’s a slight fall-off towards the corners at the widest apertures, but the corner sharpness is generally very good, especially when zoomed in to 50mm or longer.
While the results at f/4 are excellent, closing down to f/5.6 raises the bar a notch, while f/8 ensures superb corner sharpness. By f/22, there’s slight softening due to diffraction, but it’s not unusually problematic, and I would use the setting if I needed to get the maximum depth of field.
Getting close to a subject and shooting at a wide aperture gives some subject separation, but I longed to open up to f//2.8 when shooting head and shoulder portraits. That said, the background blur is attractive, and the bokeh isn’t especially ‘busy’ or distracting; the out-of-focus highlights also look pleasantly round.
It’s now standard practice to use correction profiles to iron out issues like vignetting and curvilinear distortion. These corrections are baked into the Jpegs files, but they can be deactivated when processing the raw files if you wish. Turning off the profiles applied to raw files captured with the Sony FE 20-70mm F4 G mounted on the A7R V reveals that there’s relatively significant barrel distortion at focal lengths shorter than around 35mm, and there’s mild pincushion distortion at focal lengths longer than 35mm. This distortion makes straight lines bend one way or another, but the lines are straight when the profile is applied.
Correcting curvilinear distortion involves some cropping, so, for example, a shot captured at 20mm will contain more at the corners without the profile than with. However, the profiles are applied in-camera, and their impact is visible in the viewfinder, so you compose accordingly.
Turning off the profile also introduces pronounced corner shading at the very outer corners of images shot at 20mm. But it’s not apparent at 24mm, and the correction profile is very effective at 20mm.
Naturally, you can force the issue, but the Sony FE 20-70mm F4 G controls flare well, so it’s not a significant problem even at the widest end. Chromatic aberration is also kept in check.
