Micro four thirds - does the crop factor apply to MFT lenses as well?

Started Dec 29, 2012 | Questions thread
zorgon
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Re: Micro four thirds - does the crop factor apply to MFT lenses as well?
In reply to patrickestarian, Dec 31, 2012

patrickestarian wrote:

To calculate the focal length and the aperture of a non-mft lens on mft sensors we use a crop factor of x2.

Now I wonder how the aperture number on the "original" mft lenses are calculated? are they before considering the crop factor or after that? For example, when an original mft lens is set on 2.8 is it really 2.8? or 5.6? because those lenses are meant to be used for MFT cameras only and you would think that there is no point of printing 2.8 on the lens when it always means nothing but 5.6.

I don't mean to be picky but ; When you mount a non mft lens to a mft camera,

-The focal length stays the same

-The aperture stays the same

-The depth of field (DOF) stays the same

The only thing that changes is the field of view due to the smaller sensor.

e.g it is not accurate to say that a 100mm lens on MFT is the same as a 200mm lens on FF, but you can say that they give an equivalent field of view.

Likewise, it is incorrect to say that MFT reduces the DOF over FF as the lens itself does not change. But e.g. if you were using a 100mm lens on the MFT system, this would have smaller DOF compared to a 200mm lens on FF (given the same aperture).

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