Fujifilm GFX 50S has a Fujifilm G lens mount and currently there are 15 native lenses available for this mount.
The latest released lenses that are compatible with the GFX 50S are the Fujifilm GF 20-35mm F4 R WR, the Fujifilm GF 35-70mm F4.5-5.6 WR and the Fujifilm GF 80mm F1.7 R WR.
Fujifilm GFX 50S doesn't have a sensor based image stabilization system but
4 of these lenses already comes with optical image stabilization.
Since Fujifilm GFX 50S has a Medium format sensor, it has a focal length multiplier of 0.79x 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 GFX 50S.
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Fujifilm GFX 50S Lenses with Image Stabilization
Fujifilm GFX 50S Lenses with Weather Sealings