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Comparing f2.8 on different formats is actually more complex than it seems. In terms of exposure settings f2.8 is the same on all formats, therefore if your exposure is 1/1000 f2.8 ISO 200 on m4/3 it will be 1/1000 f2.8 ISO 200 on FF (in theory and assuming the cameras meter the same). However, in terms of total light gathering then the FF camera will gather 4 times more light and hence why FF cameras handle noise better.
Of course then comes the whole DOF/FOV issue, but this isn't really down to the aperture of the lens and due to focal length and subject distances due to the crop factor.
That being said, I'm happy enough to compare say my 12-40mm f2.8 Olympus to my 24-70mm f2.8 Nikon, it's a close enough comparison for me. Both are excellent lenses and both have their pros and cons. |
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