My First L lens Advise

[Mick5]

Hi i just bought my first L lens 70-200mm IS F/4
when i try to take Shot i can hear IS sound keep coming even i got Focused Beep sound but IS sound still coming
is it normal or some problem with lens?
One more question i was double minded whether to go for 70-300L or 70-200 IS f/4 because i like nature and bird, But sales man told me 70-300 has one more gap only and 70-200 is more sharper then 70-300L
I still have 14 days to decide.
What you guys suggest ?
Thanks in advance

[TomTomTuning]

The lens will continue to stabilize even after you've "half-clicked" and got your focus.

I don't know anything about the 70-300, but from what I have read the F4 version of the 70-200 is very sharp.

[jeppoy]

Yes, the F4L IS is loud not like the 2.8L IS II which has a dead silent stabilizer. In comparison on both the F4 and 2.8 II, you can hardly tell the difference.

[gonzogolf]

The 70-200 isnt long enough for bird shots. Its a better lens, but not long enough for birds. You need a minimum of 300 for a good birding lens.