RF 100-400 and teleconverter, same issue as 100-500?

Started 4 months ago | Discussions thread
Wing2 Regular Member • Posts: 464
Re: RF 100-400 and teleconverter, same issue as 100-500?

John Sheehy wrote:

Wing2 wrote:

The 2x converter sounds like a better match for lens with such wide zoom range

1.4x's main useful range is 400-560, 160mm extra reach

2x's main useful range is 400-800, 400mm extra reach

Yes, 2x is darker, but not a full stop darker between 400-560mm. According to CameraLabs.com's test, this lens has a f number of 7.1 from 156-259mm and f8 from 259 to 400mm

Another way to look at those numbers is that without a TC, 400mm would have a maximum aperture of f/8; with a 1.4x 400mm would be about f/11.3 (8*1.414), and with a 2x, 400mm would be about f/14.254 (7.127*2).

I already pre-ordered this lens for some tele macro application. Am consider getting a tele-converter to further increase its magnification.

2x would give a 0.82 magnification that is quite near 1:1

On further study, I found the 2x converter could  actually be nearly as bright as 1.4x converter between 200-312mm range

This is lens is f5,6 between 100-113mm giving f11 at 200 to 226mm when 2x converter is added

The same zoom range when 1.4x is added the lens a between f6.3. and f7.1, giving f9-f10 brightness

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