Jostein schrieb: > > Folks, > > During the last solar eclipse, I used a 2x TC on a lens stopped down to > f/45. > > Could anyone help me out on the effective f-stop for this combination?
>From stop to stop you can easily calculate with the square root of two, or approximately 1,41. Try it: 1,4 2 2,8 ... 45 64 90 128 (rounded) So it should be around 90, which is also you TC x F-stop or 2x45 = 90 ! :-) Cheers, Thomas
