New Sigma C 100-400mm Lens OR 2x Teleconverter for 70-200 f2.8 boost?

hi Guys,

So I mainly do travel photography and mostly day time shooting.

I have the Sigma 70-200 f2.8 Full Fame v2 lens which is great and it performed really well but as I do not use the 2.8 apature day time so I was thinking of getting a 2x teleconverter to boost the lens to 400mm.

This will be only a £80 cost as there are tons of second hand ones in market and I even found out.

Another option is to buy the Sigma new C 100-400 lens as 600 will be too much to carry.

So what you guys think?

please advise and give me your opinions.

cheers
Asif

I don't know about Sigma lenses, but I tried the Canon 70-200 2.8 with a Canon 2x and it was horrible. It slowed AF to the point of being completely useless.

I used the Sigma 70-200 2.8 with the Sigma 2X TC and thought it was OK, using it on a 20D. With a 1D4 or 5D4 it would be significantly better.
Since a used Sigma TC is so cheap you might as well find out if it satisfies you. The old APO EX DG is optically very good.