70-200mm f2.8 users...

[fracster]

My sigma 1.4 would not work on my nikon lenses, my Nikon 1.7 would not work on my Sigma 120-300.

I would be inclined to try it before you buy Phil.

 

[Phil Young]

My sigma 1.4 would not work on my nikon lenses, my Nikon 1.7 would not work on my Sigma 120-300.

I would be inclined to try it before you buy Phil.

Blast.

That throws a spanner in the works...

 

[Phil Young]

I thought of another option...

Nikon J1 with FT1 adapter.

My 200mm lens will have the same FOV as a 450mm on my D7000.

OK - I'd have to keep the ISO down to below 800-1600 I imagine, but this could be an option...

 

[Soda Farl]

My sigma 1.4 would not work on my nikon lenses, my Nikon 1.7 would not work on my Sigma 120-300.

I would be inclined to try it before you buy Phil.

This is correct unfortunately the sigma teles will only work with sigma glass. Kenko do teles that work with both but not having used them I don't know how good they are although the 1.4 seems to get good reviews.