Once one makes the major camera choice, generally either Canon or Nikon (Canon for me), you will confront the large world of lenses with varying functions, designs, weights, costs, etc. The oft repeated question in the bird photography world is which is the best or ultimate birding lens. I can’t answer this for everyone, but I have come to a conclusion for me. Here were my criteria: 1) I wanted a lens that I could carry and use without a tripod. One of the joys of birding for me is mobility; the ability to hike several miles through various habitats. Remember, in addition to camera and lens one will be carrying binoculars, guidebook, water, etc. I feel sorry for the birders I see on the trail so heavily burdened the the endless additional gear and large telephotos. 2) I wanted a lens I could afford. Yes, you can take out a second mortgage or dip into retirement savings for a lens, and some do, but I did not. Having said this, I believe the lens quality is the single greatest factor in getting great photos, even more important than the camera. I recommend the best your budget allows. 3) How will use the lens–is it soley for birding or will you be using it for travel, landscapes, people, etc.?
My current lens that meets these criteria is the Canon 4oomm F5.6L. This is a old Canon model that they seemingly cannot terminate due to its popularity. It, along with their 100-400 zoom lenses, is just about the heaviest and largest lens you can carry and shoot hand-held. Although it is not cheap its price is at the low end of their L series, available for about $1200. The quality, (sharpness, build, etc.) is superb. Various sites can tell you the exact quality testings specs, but you’ll see the resulting shots are great. Its shortcomings are minor in my experience but include absent zoom function, absent weather sealing, absent image stabilization, and F5.6 aperture. This lens performs superbly in conditions with good light, but you’ll struggle in poorly lit (deep forest or cloudy) settings to get your exposure speeds fast enough for bird photography. In well lit settings, with exposure speeds >1/800 sec., the images will be great.
I came to this lens after first using the Canon 70-200mm F4L, without and with an 1.4 extender. This also is a sharp, well-constructed lens, but just did not have the “reach” I wanted for birding. I also have the Canon 70-300mm F4-5.6L. I bought this lens and took it to Argentina, leaving the 400 home, as a “combo lens” suitable for birding and also general sightseeing, landscapes, and people. Again Canon makes a superb product in their L glass series and I got some great shots, but there were numerous occasions when I missed the great bird shot due to the reach. Some have called this lens the best African safari lens, and it may well be, but when I go birding I invariably take the 400.
Canon has just released the new version of its 100-400mm F4.5-5.6L IS II for $2200. For a reasonable price increase it has addressed and corrected the shortcomings of the 400 prime. Just when you thought you had it all figured out, they get you again, and “lens envy” again rears its ugly head. I’ll try to resist for as long as possible, but the handwriting is on the wall, C’est la vie.