Upon learning that an Olympus 12-200mm with a 16.6x zoom will not be produce an equivalent or better zoom range as a Canon 70-300mm (see my previous question), I now pose the question:

Would it make sense technically to use an MFT to EF mount speedbooster (metabones 0.64x) on my MFT camera with an EF lens to achieve the zoom I want without exceeding a 1000 US$ budget?

I like the MFT format because the lenses are smaller, lighter and less expensive for the most part, however if an EF lens with a speedbooster will give me more zoom I should consider those too.

Why is this so confusing for me? I know the math seems simple to you guys but it's hard for me to grasp anything in the beginning. Give me time and I will get it, but right now I'm still working on 'getting it'.

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    \$\begingroup\$ idk about for MFT specifically, but you can buy a 150-600mm zoom for 1000 bucks. \$\endgroup\$
    – Tetsujin
    Mar 2, 2021 at 20:11
  • \$\begingroup\$ After much contemplation I think I'm going to go with an mft lens instead of a full frame one. \$\endgroup\$ Mar 4, 2021 at 0:32

2 Answers 2


A speed booster increases aperture at the expense of magnification. “Speed” comes at the expense of magnification. Wider aperture for shorter focal length. 0.64 times the given focal length in this case.

A teleconverter provides magnification at the expense of aperture. At a constant distance a 1.4x teleconverter doubles the number of pixels of the subject at the cost of one stop of light. A 2x teleconverter quadruples the number of pixels at the expense of two stops of light.

A 300mm f4 lens with a 2x teleconverter becomes a 600mm f8 “lens.”

  • \$\begingroup\$ Awesome, thanks Bob. I'm starting to get it, finally lol:) \$\endgroup\$ Mar 2, 2021 at 20:39

If, as you suggest in your comment to the question, you get a 120-600mm EF mount lens and attach it to a 0.64X speedbooster attached to a Micro Four-Thirds camera, it would give the same diagonal angle of view as a 96-480mm lens on the Canon 80D (which you mentioned in your previous, related question).

To get the same diagonal angle of view that you're getting with 300mm on the Canon 80D (mentioned in your other question), you need a 240mm lens on a Micro Four-Thirds camera.

For any focal length, all you need to do is multiply the focal length of a MFT lens by 1.25X to get the lens you'd need for the same view on a Canon 1.6X APS-C body such as the 80D.

Conversely, you can take the focal length of any lens used on the Canon 80D and multiply it by 0.8X (which is the reciprocal of 1.25X) to see the focal length lens you'll need to get the same diagonal angle of view on an MFT camera.

With a 0.64X speedbooster on the MFT camera the conversion factors are:

Multiply the the focal length of the lens attached to the speedbooster and MFT camera by 0.8 (0.64 x 1.25 = 0.8) to find the focal length you'd need to get the same angle of view on an 80D or other 1.6X APS-C camera.

Multiply the focal length of a lens used on the 80D by 1.25 (1/.64 x 0.8 = 1.25) to see what focal length lens you'd need to use to get the same angle of view when using a lens plus speedbooster on the MFT camera.

  • \$\begingroup\$ Thanks for the clear explanation Michael!:) What an awesome group of people here. I wish I would have found this community a year ago when I started this journey. I'm just grateful I'm here:). \$\endgroup\$ Mar 3, 2021 at 9:31

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