October 28, 2014 at 8:39AM


Metabones Speedbooster F-Stop Question

I apologize if this has been discussed elsewhere or is simply too much of a "newb" question for some to handle, but I wasn't able to really find any definitive answers elsewhere on the internet to tell me more about the basics of using the Speedbooster and no "guide" was provided with the product. A big reason of making the jump to buying my own gear was to learn as much as possible about the technical side of filmmaking so I am fairly new to many things in this regard.

Currently using the Panasonic GH4 with the Nikon to M43 Speedbooster coupled with the excellent Sigma 18 - 35mm F1.8. My question comes down to how the Speedbooster defines the F-Stop on the adapter and whether or not I've been reading it wrong.

As we all know, the Speedbooster provides another full stop of light, effectively turning my Sigma lens into an f1.2 lens (please correct me if I'm wrong). It's safe to assume that when set to "F" on the adapter we're wide open at f1.2. Now, does each increment onwards represent a full stop or a half stop? Is "1" now f1.8? F1.4? I'm simply trying to find out exactly how to read this while shooting, especially if I'm shooting two cameras with a friend of mine who isn't using the same lens/adapter setup as me to match our exposure as accurately as possible.

Thanks, guys. Any help would be really appreciated!

1 Comment

Yes, your Sigma lens becomes 1 F-stop faster so f/1.8 becomes f/1.3

Each marking on the Metabones Speedbooster represents closing down 1 F-stop, so marking 3 represents 3 F-stops down from Full aperture.

October 28, 2014 at 1:48PM, Edited October 28, 1:48PM

Guy McLoughlin
Video Producer

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