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How to calculate FOV 35mm equivalent with speedbooster and APS-C Lenses??

Started Feb 9, 2017 | Questions thread
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wikid247 New Member • Posts: 1
How to calculate FOV 35mm equivalent with speedbooster and APS-C Lenses??

Hey so I'm trying to understand how to calculate 35mm equivalent focal length so when I buy new lenses I can use them on both my Sony A7S II (full frame) as well as my GH4 (with metabones ultra 0.71x speedbooster). I only have Canon glass so I share it between the two cameras.

I'm trying to understand how to calculate in my head what the 35mm equivalent focal length difference would be on a GH4 with Metabones adapter so I know what camera I want to bring with me on a shoot day.

I know how to calculate 35mm equivalent focal length for full frame glass on a GH4:

FF Lens Focal Length * Speedbooster crop 0.71 * M43 2x crop = 35mm equivalent Focal Length

For example I have a Sigma 35mm f/1.4 (FF), does that mean it's:
35 * 0.71 * 2 = 49.7mm equivalent on 35mm frame?

But I don't know if that applies the same for APS-C lenses, is the formula the same as above or is it different?
I have a Tokina 11mm-16mm (APS-C), so on a gh4 would it be:
15.6mm-22.7mm for 35mm equivalent or am I calculating it wrong?

Thanks all!

ANSWER:
This question has not been answered yet.
Panasonic Lumix DMC-GH4 Sony a7S II
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