[arvydas]

No, at least not exactly. You can not be sure about the focal length at MFD nor FOV at MFD (those are not linked 1 on 1).

It is very difficult to determine the actual focal length... And even if the focal length stayed constant, you would get a more narrow FOV at MFD than at infinity... 

 

   Hm....  For macro lenses at MFD (_well, usually_) we have ratio 1:1, so 36mm object projects on 36mm sensor at the MFD, and what actually means the same FOV for different macro lenses at this magnification (1:1). Sensor size doesn't change, and we know both MFD and magnification (and thus max. object size, that could be projected on the sensor at that particular distance) for every lens from manufacturer's specifications. So, we have isosceles trapezoid  with further calculations arising from it, instead of classic calculation of the FOV, where we need FL. Of course, indicated magnification may not be very precise (Popphoto tests), but we can measure it more easily than real FL, and on this approach we even do not need focal length of the lens.

    Unfortunately, I am not so good in math to further elaborate that.

 

A.