So I now have a 70-200 L IS f4, a Sigma 150-600, and a Tokina 11-16. Next I need a good walking around lens for when I can't carry all my gear with me. I shoot landscapes, wildlife and birds. My current lens is the kit 18-55 which is ok but not as good as I'd like. Any suggestions that don't cost a fortune and would give me a good range? It's for a crop sensor camera.