A little test shot at the full 300mm, with a Sigma DL F/4.5-6.7 100-300mm zoom lens, at 1250 ISO on my K1. This lens was bought as a set of 2 (with the DL 28-80mm Macro from the same series), both in mint condition, for £20 on ebay, so you could say the lens stands me to £10. It's pretty remarkable considering the price and is sharp from 100mm all the way to 300mm, as long as you're sensible with the aperture setting.