Best lenses for the Olympus OM-D E-M1: Short telephoto and standard focal lengthsBy Kevin Carter - Friday November 29 2013 Lens Recommendations
Although the Leica designed 25mm f1.4 has a DxOMark score of 24, compared with 21 points for the new 20mm f1.7 II upgraded model from Panasonic the image quality is closer than you might think. The same goes for the Sigma 30mm f2.8. It's a good performer optically when compared with the 20mm f1.7 but there’s quite a gap when comparing the Sigma with the Leica 25mm.
|Panasonic Leica Summilux DG 25mm F1.4||579||24||11|
|Panasonic Lumix G 20mm F1.7 ASPH||400||22||11|
|Panasonic Lumix G 20mm F1.7 II ASPH||400||21||10|
|Sigma 30mm F2.8 DN A Mount 43||199||18||8|
|Sigma 19mm F2.8 DN A Mount 43||199||18||7|
|Sigma 19mm F2.8 EX DN Micro 4/3||166||16||6|
Be that as it may, the Sigma may not have the benefit of a large maximum aperture but it’s sharp wide-open, albeit in the center.
At the same aperture the other two are sharper still and Leica is far ahead in corner sharpness by then. As well as the advantage in Transmission of the Leica it has good control of vignetting unlike the new 20mm, however that has the lowest chromatic aberration of the three.
In fact CA is somewhat troublesome on the Sigma with it being noticeable in the outer 50% of the field (i.e. the periphery, edges and corners). Based on price and performance, the new 20mm f1.7 might not perform quite as well as its illustrious predecessor but out of the three models it’s probably the best value.