Panasonic Lumix G 20mm f/1.7 ASPH VS 30mm f/2.8 EX DN Lens sharpness comparison by Fredrik Gløckner

From my own findings, there's the issue of Sigma's much lower CA and purple fringing when used on Olympus bodies. In any case, the Sigma is an automatic buy anyway, due to its current very low price.

"We see that the Lumix G 20mm f/1.7 has an impressive level of sharpness, even wide open. The Sigma 19mm, on the other hand, needs a bit of stopping down before reaching the same level of sharpness. At f/2.8, the 19mm lens is a tad bit dull, even in the centre of the image frame. This finding is consistent with other tests I have seen. Generally, it is observed that the Sigma 19mm lens is not the sharpest at f/2.8, and improves when stopped down to f/4 and f/5.6. Stopping down beyond f/5.6 does generally not add anything to the overall sharpness, but does give you more depth of focus (DoF). If you need a deep DoF, it may still be wise to stop down to f/8 or even further, but this will give you slightly worse sharpness at pixel level.


Still, it makes sense to say that both lenses are sharp. Comparing the Sigma lens with the Lumix G 20mm f/1.7 is perhaps a bit unfair, since the latter is known to be very sharp. For most uses, the Sigma lens is certainly sharp enough.

On the positive side, the Sigma 19mm f/2.8 EX DN appears to handle flare a tad bit better. There is less flare effects around the strong highlights"

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