When I was looking for a walkabout lens around the range of 80-400mm with image stabilizer, I had several choices. It was either the Sigma 120-400 OS, 150-500 OS or the Nikkor 80-400vr. After initial testing of the three lenses, I narrowed down to either the 150-500 OS or the Nikkor 80-400vr.

There were two factors that I deem as priorities for choosing the lens. First, sharpness wide open. Second, focus speed for flight/action.

In the store, I compared the two lenses with the Nikon D3 in the following areas.

1. Focus speed (Sigma Wins)
2. Sharpness (Tied – wide open)
3. Colour (Nikon wins)
4. Image stabilizing (Tied) (lowest speed tested being 1/160th)

Based on the above results, and of course, the price tag, I chose the Sigma. The Nikon costs about $1000 more than the Sigma.

Here are some results over the last month shooting with the Sigma 150-500f/5.6-6.3 HSM DG OS and Nikon D3/D300.

Nikon D3 + Sigma 150-500f/5.6-6.3 HSM DG OS
Picture 1(Scarlet backed flowerpecker)

Picture 2(Stork billed Kingfisher)

Nikon D300 + Sigma 150-500f/5.6-6.3 HSM DG OS

Picture 3

Picture 4

Disclaimer
The findings above are the sole experience of mine and the copy I possess and does not represent all the Sigma lenses in the market. As such, I expect results to differ.