Sigma 35mm f/1.4 not working with metabones speedbooster xl ef-m4/3

Started 3 months ago | Discussions thread
MOD Tom Caldwell Forum Pro • Posts: 31,040
Re: Sigma 35mm f/1.4 not working with metabones speedbooster xl ef-m4/3

A Furry Peanut wrote:

The aperture seems to only go as far as 1.4, but with the speedbooster xl, this should be larger by 1.3 stops. I checked the metabones website and the lens was not listed in their compatibility list, but they did mention that their speedbooster should work with most ef lenses. Does anyone know if the speedbooster just doesn't work with the sigma 35 or if there is something wrong with my speedbooster?

The aperture that is actually available is rounded by the firmware for display.  Presumably the true calculated aparture is somewhere between f1.3 and f1.4 and has been rounded to f1.4 for display purposes.

I am not an expert but as far as I know it is probably not a given that all lens apertures fall into the convenient accepted stop sizes - expecially at maximum and minimum and therefore the manufacturers will set the normal scales to the nearest standard scale size.

For example a maximum aperture of f1.25 might be reasonably shown on a mechanical scale as the conventional "f1.2" rather than "f1.4".

A camera body might only provide conventional stop read-out and therefore may not be capable of showing f1.3.  But my 50-100mm f1.8 Sigma does show f1.3 when focal reduced on a M4/3 body.

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Tom Caldwell

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