Even though Canon's EF 400mm f/5.6 USM is the cheapest super telephoto option out there for auto focus lenses, it's still a little too rich for my blood, especially if I can get a faster lens for less.
That's why I'm considering the Canon FD 400mm f/4.5
or the Tamron Adaptall SP 400mm f/4.0 LD-IF
. For either I would have to buy an adapter of sorts, and for nearly the same price. And I know the FD-to-EF adapter would add some telephoto reach and slower light in order to maintain infinity focus. But, how does the tamron adapter work? Would it behave in a way that I maintain 400mm and f/4.0?
Although both of these lenses are known for sharp resolution, these are old and rare lenses ... but I hope a few of y'all have some valuable feedback.
Personally, I'm leaning towards the Tamron. Anyone suggests differently?