Is the Sony FE 24-70mm f/2.8 GM the standard zoom lens Alpha 7-series users have been waiting for? Michael Topham finds out
Sony FE 24-70mm f/2.8 GM – Image quality
Those contemplating buying this lens will be pleased to read that it performs as well as its price suggests it should. It resolves a mesmerising level of detail and comparing the results taken on this lens against those taken on the Sony FE 24-70mm f/4 ZA OSS revealed there’s no contest as to which is the superior optic. In isolation, the detail resolved by the 24-70mm f/4 lens seems acceptable, but it’s not until shots are viewed side by side that you realise the sharpness of this lens is in an entirely different league.
Running the lens through our lab produced a strong set of MTF curves that tell us it’s super sharp at the widest end of the focal length and only slightly softer when you push through the zoom range. Centre sharpness peaks around f/4 at 24mm, with corner sharpness improving all the time the lens is closed down towards f/8. The sharpness in the centre at 70mm doesn’t quite match the figures recorded at 24mm or 50mm, but it improves when the lens is closed down towards f/5.6. As a general rule, the sweet spot of sharpness is found between f/5.6-f/8 and it’s only as you start to push beyond f/11 that the introduction of diffraction sees the level of detail tail off.
With all lens compensation switched off on the camera, I did identify some purple and green aberrations, but the fringing that appeared along branches of trees were quickly dealt with in Lightroom. Vignetting isn’t a major cause for concern at mid to full telephoto lengths, but is more obvious when the lens is used wide open at 24mm. Corners appear approximately 1.5EV darker than the centre of the frame when the lens set to f/2.8 at 24mm and to banish this from wideangle images you’ll ideally want to stop the lens down by one or two stops. Barrel distortion at 24mm disappears quickly as you move through the zoom range, but is replaced by pincushion distortion as you push towards 50mm and 70mm.
Our Applied Imaging tests show the lens is super-sharp in the centre at 24mm, with corner sharpness peaking at f/8. Sharpness in the centre isn’t quite as high at 50mm or 70mm, but a close inspection of the graph reveals that edge sharpness improves considerably when it’s closed down towards f/5.6 and f/8. The sharpest results on this lens will be captured between its f/5.6-f/8 sweet spot, with diffraction softening the finest details beyond f/11.
The lens displays obvious vignetting when the lens is wide open at 24mm, with the corners appearing approximately -1.5EV darker than the centre of the frame. This improves to -0.8EV at f/4 and beyond this it shouldn’t be a concern. Vignetting is less dramatic at longer focal lengths, with corners appearing approximately 0.5EV darker than the centre at f/2.8 and is absent at f/4 and beyond.
At 24mm, there’s some noticeable barrel distortion present, with the straight lines of our test chart bowing outwards. This distortion starts to disappear around 30mm, with pincushion distortion becoming ever more prevalent as you push towards 50mm and 70mm. Users will want to tick the Enable Lens Profile Corrections option in Lightroom and Camera Raw to remove curvilinear distortion, but at the time of writing a profile for the lens wasn’t currently available.