Hi I was just wondering if anyone has any experience using this lens. I bought it a few months ago and have only really got started properly with wildlife photography. I have played around with settings a bit now and can get acceptable results but still nothing great. I mostly shoot handheld with ISO around 800 shutter speed of at least 1/500 F5.6 but still most of my shots are a bit blurry. Has anyone used this lens with good results or is it time to save and upgrade my lens?