Default SkyrimPrefs.ini settings (vanilla presets):
iBlurDeferredShadowMask = 3 ;higher values 'bur' shadows and decrease resolution, but also decreases edge pixellation ... ideally, this should remainl rather low, but who knows for sure?
iShadowMapResolutionPrimary = 2048
iShadowMapResolutionSecondary = 1024
iShadowSplitCount = 2
fShadowLODStartFade = 200.0000
bShadowMaskZPrepass = 0
fShadowBiasScale = 0.1500
iShadowMaskQuarter = 4