two special questions about GI in yafray


i have to specific questions about yafray:

first: i realized that only when i turn shadow treshold off (1)
i get everywhere clean edges and shadows.

for example here
you see not only the shadow along the blade but also the edge along the handle shows some blotches.

i noticed that treshold off rendertime also increases a lot.

second: i read that using additional helper like the photon panel in the GI panel or additional photon lamps will help out. i tried it but never got any different render result. do i miss a point here?