After finding that my 80-200 f/2.8D lens backfocuses when at f2.8 and within 10-15'. See this thread:
decided it was time to get a lens that would work well for the butterfly shots that are on the first pic of the link. I like this lens it takes some great pics but is not so good wide open and close (for a 200mm).
One of the lenses I have been looking at is the Sigma 50-150 f/2.8 new version, it comes well rated. Decided against the 80-200 AFS with issues around parts, example focus motor is no longer available. Suppose the 70-200 f/4 may also fit into the range but but not sure about the f/4 part, photozone lists the equivalent aperture in terms of DoF as f/6 as compared to f/4.2 for an f/2.8 on FF.
Any other suggestions. Budget $1K ish.