Measured on a 24Mpix Sony Alpha 900, the 500mm f4 G has a DxOMark score of 20, slightly lower than we might have anticipated in a high-grade lens like this. If you look at the Metric scores individually, the Sharpness score is a slightly disappointing 16P-Mpix, 30-percent below the 24P-Mpix potential maximum that could be achieved on the Alpha 900. But that’s a collective function of the camera sensor and lens, and a more efficient sensor may have produced a higher result.
Of course what matters on a lens like this, especially as one as pricey as this, is the performance at maximum aperture. While sharpness is a bit on the low side, it is extraordinarily homogenous across the imaging field at f/4; you won’t notice any difference in images at 100-percent on screen or in prints viewed up-close. In fact, the difference is less than 1% measured from the centre to the corners and an excellent result.
Slight pincushion distortion can be measured but it’s not noticeable in real world use, and neither vignetting nor chromatic aberration are likely to be problematic and well within expected tolerances.
The transmission score, measured at 4.3Tstops (on the Sony Alpha 900) is a little lower than expected and disappointing given the lower number of elements (11 elements in 10 groups) used. Both the Nikon and Canon lenses feature optical image stabilization and have a higher quantity of glass elements in their construction, 16 in 12 groups in the case of the Canon.