Advantages
1. Light in Weight - the Canon EF 400mm f/5.6 L USM Lens is light in weight compared to the other Canon telephoto lenses . This is a huge advantage for bird photography, easy to maneuver when taking flight shots, not too tiring when trekking.
2. Excellent Optical Performance - as a member of the Canon L Lens Series, the Canon EF 400mm f/5.6 L USM Lens' overall optical performance is outstanding.
3. Fast focusing - thanks to the Ultrasonic Motor (USM), the 400 f/5.6 L internally focuses very fast and very quietly.
4. Sharp Images - the Canon EF 400mm f/5.6 L USM Lens performs superbly in the sharpness department. Even wide open, the 400 f/5.6 produces very sharp images.
5. Good Vignetting Performance - even the corners of full fame shots remain evenly colored without displaying any tendency to vignetting.
Disadvantages
1. Image Stabilisation - one of the compromises of this budget lens is that it doesn't have image stabilisation (IS). It can still be very successful for "handheld" or so-called "grab-shots" provided that a short exposure time and/or a higher ISO is used. When used together with the high quality EOS DSLR's recently introduced by Canon, this disadvantage can be compensated.
2. Water Resistance - another disadvantage of this lens is that it isn't 100% water resistant like its more expensive cousins.
Conclusion
The
Canon EF 400mm f/5.6 L USM Lens is hugely successful for bird and wildlife photography and especially for flight shots. It offers a good level of performance at a relatively low price. Check out the quality of sample images on
Ken Billington's Bird & Wildlife Photography