The 400 prime
After playing with both the Canon 100-400mm f4.5-5.6 IS and the Canon 400mm f5.6, I've decided to go with the fixed 400.
It was not an easy decision. Both lenses are very nice and in the same price range. They each have their pros and cons, which are well-discussed on internet forums. Here are some of the major points:
Pro zoom:
- versatility from 100mm to 400mm
- Image Stabilization
- close focus to 6 feet (versus 11.5 feet of the prime)
- better low-light performance thanks to the IS
Pro fixed:
- lighter and less bulky
- sharper at 400mm (though some on internet forums dispute this...my field tests showed the prime sharper, as expected)
- great image quality when shot "wide open" at f5.6
- fast autofocus (key for birds in flight)
- better built-in hood
- fewer moving parts, so fewer issues with dust, moisture, and breakdown
- better performance with a teleconverter than the zoom
Defenders of both lenses make convincing arguments:
Zoo...