i'm having trouble with this lens, for some reason when i go to 300mm, its REALLY hard to take sharp picture unless i'm in full sun, which THEN i still need a lens hood, because the picture gets screwed up from the sun up top. once the shutter speed goes above 1/250, its impossible for me to take a shot. any recommendation? any exercise or something you guys do to keep the camera steady? even the cheap tripod i have shake when its at 300mm. help please.