I second this question... I always avoid swapping lenses in the open. When ever I can, I carry two bodies with the glass I think I will be using or swap lenses inside my car or a building (some buildings are not so clean!!!). I always try to keep the camera bodies facing down and keep the rear lens cap at hand as to cover theexposedrear element as fast as I can. It will beinterestingto hear from others to shoot in the field all the time.