Im really new to dslr and im wondering if anyone can explain to me the detailed lens spec that people in the buy/sell trade alway use? I know f1.8 (lowf) means the aperture can open real wide enabling a brighter picture and making foreground and background image look focused and f25 (high f) means darker image and more focused to an object and the mm range liek 25-200mm is the zoom effect with 25mm as the least to 200mm the max range it could reach or am i wrong? the rest of the lens spec i dont understand