Hi
@Moose - First of all, thank you very much for all your help. I learned so many things from this forum. I am interested in bird watching and I am very much interested in photography. Recently I had bought the D3100 with kit lens and added the 55-200mm non VR lens recently. I tried taking photos of some birds, but the 55-200mm lens doesn't have enough reach. Could you suggest some other lenses with better reach. I am bit constrained with budget (cheaper would be great).
Comments
In addition to the Sigma, you might also take a look at the Tamron AF 70-300mm f/4.0-5.6 Di LD Macro (see here). These lenses are nearly identical in terms of sharpness, focusing speed and overall performance. Check to see which lens is more affordable in your area, I would give either one a try. Happy shooting! :)
Then theres teleconverters - you would have to make sure it is compatible with your lens. I have a Sanyo x1.7 lens which attaches to the front of the main lens, and thats nicely effective, altough theres a bit of drop in quality with the D3100.
I treat (treated?) myself to the new Fujiflm HS30 (I already have the HS10 and thought I'd upgrade) and that is excellent for stuff like birding, especially with the Sanyo attached, its as if they were made to go together! The lens on the HS30 gives about 30x, so I suppose I'm getting about 45/46 times zoom with it. Worth considering if you want extra zoom? (Tip: genuine spare battery is £60! Get a 'copy' for £12 on ebay - they work OK!)
"Nikon D90 + Tamron 70-300 VC USD + Kenko 1.4x TC"
I have the lens you mention and I find it excellent, not just for birding but for general use as well.
You can read about the 55-300 here:
http://www.kenrockwell.com/nikon/55-300mm.htm
and he also mentions the 70-300 and gives a link to it.
Also, if you go to Moose's 'old' D3100 page, you can search (Ctrl-F) for references to lenses:
http://www.cameratips.com/d3100/nikon-d3100-forum