> Putting a 500mm lens in front of a 400mm lens focussed at infinity,
> produces a magnification of 500/400 = 1.25 times. If you focus at
> 500mm, the field of view should be 1.25 x [36mm,24mm] = [45mm,30mm]
>
> If you had indeed used enough extension tubes or bellow to let the
> 400mm lens focus to 0.5m, the effective aperture is a mere f/28 !!!
Just wanted to note that with my EF 75-300 and Kenko 2X I can get 1:1 at
1.5 metres minimum focus distance at 300mm. Wide open aperture is F11.
Manual focus only, but it's a great way to get in close, cheaply. (as well
as giving me a 600mm lens for distant subjects) Nit-picking
sharpness freaks note: I'm very very pleased with the sharpness of this
setup :-)
I might try adding an extension tube and go shoot something really
small... waiting for the bugs to come out right now though...
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