Yup I've discuss with MM about the 100-400 F4L IS too but if I sell my lens now I probably be at a loss. Bought $1636 less than month i if u let go $1300 sure got people make if ex. Mist probably like what MM said to me. Understand the lens and my body for the time being when got extra $$$ then upgrade. Btw dies lens filter size big small make any different? Is it the bigger the better light going into the lens? Keke.