Olympus E-PL1s has a Micro Four Thirds lens mount and currently there are 132 native lenses available for this mount.
The latest released lenses that are compatible with the E-PL1s are the Brightin Star 60mm f2.8 II, the 7Artisans 50mm f1.2 APS-C and the Pergear 50mm F1.2 APS-C.
E-PL1s also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on the E-PL1s.
Since Olympus E-PL1s has a Four Thirds sensor, it has a focal length multiplier of 2× so you have to multiply lenses original focal length with this multiplier to find the Full Frame equivalent focal length of the lens when mounted on E-PL1s.
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Olympus E-PL1s Lenses with Image Stabilization
Olympus E-PL1s Lenses with Weather Sealings