You can never have too much reach when photographing wildlife and birds. Long lenses are expensive (to put is politely). Lately both Tamron and Sigma released 150-600mm lenses (which I mentioned a few weeks ago when talking about bird photography gear). Now that I have spent a lot of time with the Sigma I would like to give you my impressions of this lens.

         There are lots to like:

• The price is very reasonable at just below $1,100.00

• Under good conditions the lens is very sharp

• The range from 150mm to 600mm is ideal especially coupled with a crop camera (I used a Canon 70D)

• The lens is manageable, yes it is heavy but not as much as you would imagine

• A tripod collar is included

• Subjectively, it is a beautiful lens

As you can see the lens is sharp.

          There are a few things that I don't like about the lens:

• F6.3 on the long end is often problematic. Now I know they had to compromise to get the price, size, and weight down. The best light to shoot in is often just after sunrise and before sunset. This kind of light is generally not as bright as the light later on in the day. When light is already low and you have to shoot at F6.3 with a long lens you run into problems. Firstly, your shutter speed is too low. Remember to get sharp images your shutter speed generally needs to exceed the focal range of the lens; in this case 1/600. Secondly, to get to 1/600 you now have to increase your ISO which introduces noise. F4 would have been much preferred. Thirdly, this kind of lens is going to be used to shoot moving objects more often than not. To freeze moving object faster shutter speeds are needed. Lastly, see the next point ...

• I find that the backgrounds are often not blurred enough. That can be attributed to the small F.Stop, but keep in mind that long lenses generally just don't have much depth of field anyway; yet with this lens it was really difficult to get the background smooth. I just don't like the bokeh of this lens.

• Focus! On the Canon 70D the focus is fast and I have no complaints - generally speaking. BUT, then there are times when it just will not focus; even when there are good contrast areas in the image. It just hunts without even coming close to focus. It then gives up. I press the focus button again and I get the same result. I have to go through the process three of four times before it locks on and then it works fine again; until it happens again. I had this happen about four times per day (shooting all day from 6am till 6pm). I never turned off the camera or changed lenses. Speaking of focus, I hate the small focus right; the one on the Sport model is much better (off course I don't want to pay twice the price and carry double the weight).

• Ghosting or image stabilization issues abound. I found disturbing ghosting in the background of many images. At this point in time I am not sure if the ghosting is due to internal reflections (which I doubt) or due to the image stabilization system (which I suspect). Further testing needs to be done to difinitively draw a conclusion. I did not use a tripod (they don't work well inside a car) so I don't think the issue relates to image stabilization on a tripod.

Look at the top left of the image. There is clear ghosting going on.

          If I can get the ghosting sorted out I am generally happy with the lens for the price. I hope my impressions help you to figure out which one of the three models (Tamron 150-600mm; Sigma 150-600mm Contemporary; Sigma 150-600mm Sport) is best for you.