Studio tests
We tested the Canon-mount version of the Tamron SP 85mm f/1.8 Di VC USD on the 21MP Canon EOS-1Ds Mark III. The results are shown below.
Sharpness
Tamron 85mm f/1.8 Di VC USD: MTF50 vs aperture
The results from our Applied Imaging MTF tests confirm that the lens has desirable characteristics for a short telephoto portrait prime. At f/1.8 the values are relatively low due to spherical aberration, but the lens sharpens up rapidly as the aperture is closed down. Peak sharpness is at f/4-f/8, but in truth all apertures are quite useable. The traces for the corners closely match the centre, indicating excellent cross-frame sharpness.
Vignetting
Tamron 85mm f/1.8 Di VC USD: Vignetting at f/1.8
Tamron 85mm f/1.8 Di VC USD: Vignetting at f/2.8
Tamron 85mm f/1.8 Di VC USD: Vignetting at f/5.6
Some vignetting is visible wide open, with the corners of the frame 1.3 stops darker than the centre. However the very gradual falloff profile means that this is visually not unattractive; indeed it can often add to the look of your shots. Stop down to f/2.8 and the vignetting practically disappears.
Distortion
Tamron 85mm f/1.8 Di VC USD: Distortion. SMIA Tv = 0.4%
Curvilinear distortion is extremely low, with just the barest hint of pincushion distortion detectable from our test chart shots, which is typical for short telephoto primes. However while this is measurable in the lab, you’ll never see it in real-world shots; instead the lens draws subjects in a very lifelike fashion.
