We have purchased a Nikon D70, been using it for a few months to try to get used to the camera. I have the regular wide angle lens and a 100/300 zoom. I am probably going to buy a doubler for the 100/300 lens and possibly a fixed 500 mm lens. I specifically want to be able to take great pictures of birds. Would it be worth it to go ahead and get the 500 mm lens also??? (I'm talking about one that's relatively cheap--maybe $150 or so--as opposed to the fully autofocus one, which I couldn't afford, under any circumstances....) Any thoughts on photography on safaris and on the D70 in particular would be appreciated...