Wow!! I am surprised, 13 responses before mine and no one yet said that you should get the 1.4 because it's 2/3 stops faster than the 1.8. Especially shooting with the D300, the 2/3 additional stops of the 1.4 can be had by a simple ISO boost.
I think the benefits of the 1.4 over the 1.8 are these, but I am sure others can find more:
- Better focusing - lenses are by default wide open, so the more light they "see" the more it helps the focusing system of the camera
- Better build quality - 1.4 is mostly metal and 1.8 is mostly plastic
- Smaller depth of field for creative effect - this could also be a dissadvantage because with such razor thin DOF wide open it could be easy to miss focus altogether.
- Bokeh - I have only shot with the 1.4 or the 1.8, but never the same shot with both to compare, but already chimed in about that.
- Dissadvantage - 3X more expensive than the 1.8
Advantages of the 1.8 over the 1.4
- 1/3 the cost of the 1.4
- f1.8 is plenty fast for most use and @ 1.8 it's a full stop faster than the f2.8 zooms.
You will need to make a decision if spending 3X more for the 1.4 is worth the benefits you get from it. The biggest advantage I see in the 1.4 is the larger aperture as it relates to making it easier for the camera to focus.
Greg, that is a great shot.