I have a Nikon D90, with 18-105 kit lens, 55-200 kit lens, Nikon 50mm 1.8 and a Tamron 70-300 lens. I went to a zoo yesterday and the 18-105 was good for 75% of the shots. But there were several times when I had to swap to the Tamron for some of the animals that were far away. I am new to photography (about 8 months), and found it difficult to swap lens. No place to sit camera or lens, trying to remove one lens, put cap on it to protect it, hold both lens at same time, etc. I am looking at the Tamron 18-270 lens, but I am giving up 30mm. Is there a great lens out there that'll give me a range from 18 to 300, 400, or more? I've seen a 50-500, but I still wouldn't be able to get some close shots with the 50mm, like inside with the insects and fish. Am I just asking for too much? Is this just part of the fun of SLR photography? I'd appreciate your thoughts.