How does the first third-party standard zoom for Sony full frame mirrorless cameras shape up? Michael Topham had the privilege to test the first working sample in the UK
Tamron 28-75mm f/2.8 Di III RXD review: Image Quality
To understand how the lens performs optically, it was tested with both Sony’s high-resolution A7R III as well as the more recent Sony A7 III. Within a short space of time I found the lens was delivering good results, even on the most demanding full-frame sensor currently made by Sony. To view a gallery of shots, including links to full-size images visit our Tamron 28-75mm f/2.8 Di III RXD sample image gallery.
This lens’s strength is its centre sharpness. When shooting wide open at f/2.8, I found my sharpest results were achieved around 50mm. Centre sharpness improves across the zoom range by stopping down to f/4 and our Image Engineering MTF50 tests reveal it’s marginally sharper in the centre towards the middle and far end of its zoom range than it is at wide angle. Corner sharpness, especially between f/2.8 and f/4, is this lens’s weakness. To achieve the best results from edge-to-edge you’ll want to use the lens around f/8. Useable results can be obtained by stopping down to f/11, but I’d recommend giving f/16 and f/22 a wide berth as diffraction significantly reduces overall sharpness at these settings.
Uncorrected files show considerable distortion. This, as typical of a standard zoom, is of the barrel type at wideangle and quickly changes to pincushion across most of the zoom range. The good news is that the lens is compatible with many of the advanced features that are specific to certain mirrorless cameras, including in-camera lens corrections for shading, chromatic aberration and distortion. Having tested the lens with in-camera lens corrections turned on and off, all users will want to ensure in-camera corrections are activated before shooting commences.
As for vignetting, this is very prominent in uncorrected files at f/2.8. It’s not quite as severe in the middle of the zoom range as it is at either end of the zoom and reduces considerably by stopping down to f/4 or f/5.6. Stop down to f/8 and vignetting completely vanishes.
A close study of raw files revealed the lens does exhibit chromatic aberration through its zoom range. After identifying traces of green and purple fringing along some high-contrast edges, I compared uncorrected raw files beside respective JPEGs that benefited from having in-camera corrections applied. This comparison clearly showed that the fringes of colour were effectively removed in the latter.