I am of some opinion about Canon's "AI Servo AF". However, I am aware that it is a question-and-answer forum, not a discussion forum. Therefore, I will ask my question as follows:
Does any one have an objective test (or a series of tests) that clearly shows the limitations (or failures) of the Canon AI Servo AF autofocus to track and maintain focus on moving subjects?
I do not have much experience in animal photography. Maybe the "failures and limitations" are mine alone. When one looks for reports or blog posts that document the "limitations" of AI Servo AF, there is virtually nothing that is critical of his performance. Still, I have the feeling that in a relatively short time I have gathered objective evidence suggesting that Canon's Phase Detected AF system is not quite ready for prime time – in at least some applications.
I'm trying to catch small birds in flight. Difficult? Yes of course. But does that mean that Canon is receiving absolution from the community because the task is arduous? On the contrary, many online articles sponsored by Canon claim that the Canon system can handle moving subjects and flying birds. Exceptions to Canon's claims seem to be rare and pronounced in passing.
I wondered if people were reluctant to express themselves – perhaps because reviewers could not risk criticizing their sponsors, or perhaps as in this old story. I have knowledge that make bird photography for many years. When I shared my thoughts with them, the only memorable comment was: "You simply do not know how much better the current systems are than the old ones." It may be fine, but complacency and progress rarely go hand in hand!