One problem with using a powerful lens like the Canon 100-400 L is that you cannot zoom back when the subject comes in close. The kit lens in most recent Canon DSLRs is a cheap 18-55 EF lens, which for the rigours of aviation photography is not really up to the job, partially because of its slow focusing and it's annoying habit of 'hunting' at the wrong moment. I needed a better lens, espically as a lot of my photography is conducted on the well known 'mound' at the 29 approach end at Mildenhall, where heavies like the C-17 and even the KC-135 are too close to frame with a 100mm lens on a digital conversion. I have just acquired a 28-135 IS USM which plugs the gap perfectly and this C-17 was the first subject taken with it. The quality compares well with the other C-17 (Travis markings) shot on the 100-400 L lens from a nearby location a hour earlier.