ever since i bought my canon eos 5d mark II i thought about upgrading my telephoto zoom lens to something "appropriate". also with the upcoming trip to canada and the loss of the 1.6 crop factor when switching to the full frame body my old 300mm was only a 300mm lens, not the 480mm i was used to. so i searched the internet for good second hand lenses, and i found the canon L-series EF 100-400mm (f/4.5-5.6L IS USM) for a good price on a consumer-to-consumer sales services website. a thing i never had before was the "IS", the image stabilizer. i was amazed how cool this tool works and how much it can improve pictures under bad conditions - this is really awesome. also i am back to my 400mm focal length, and the maximum aperture of 4.5 to 5.6 is also quite okay. the ultrasonic motor for focusing also works like a charm. i'm super happy with lens and cannot wait to take it out for some test pictures. the only downside is the weight of 1.4 kg. this will add up to approximately 2.5 kg for my camera gear. luckily i also bought the "carry-speed prime" sling strap, so that the weight will be on my shoulder, not on my neck. having all the stuff on my shoulder feels way better than before with the old sling that came with the camera. another wonderful tool i can totally recommend for people with heavy camera gear.