Excellent wildlife lens for the price

I have this Sigma 100-300 f/4 EX APO HSM lens for almost two years now and I just love it. It is the sharpest lens I own, sharper than all three of my Nikkor lenses: the 180 mm f/2.8, the 35-70 f/2.8 and the 18-200 VR. It has worked well on both my Nikon D70 and D300 bodies.

The lens is an internal focus lens; therefore, it maintains the same length (8.8 inches) whether you're shooting at 100 mm or 300 mm. It is well built and reasonably priced. This lens is very well balanced with a nice collar. But any fast lens like this will come with some weight (51 oz), most people may like to have a monopod and a nice ball head to help alleviate the weight for long outings. But handholding the lens is definitely possible.

Image quality and focusing speed both hold up well with a Sigma 1.4X teleconverter. With the Sigma TC, focal length is automatically converted in EXIF, a bonus. Using the TC with this lens is the cheapest option for professional-like wildlife photography. I also own the Sigma 50-500 lens, aka, Bigma. But image quality is so much better with the 100-300 f/4 + the 1.4X TC, I rarely use the Bigma anymore.

I have a Kenko Pro 300 DG TC as well. But the Sigma TC works better. The Kenko TC does not convert focal length information.

You can see samples of my pictures with this lens at
http://www.flickr.com/photos/guywong/tags/sigma100300f4/