Originally posted by btnapa Thanks for the info. In that case, it is not a fair comparison. If I do not miss my guess, Pentax is over one stop from wide open, while the Bigma is wide open. To make it a more even match, the Bigma needs to go to f8 or perhaps another 1/3 or 1/2 stop more to get away from the wide open weak spot.
I compared them at the same actual apertures - in the real world, we can't control the illumination created by the Sun and shoot at the apertures we want? Here both lenses were in the same conditions.
As for sharpness "in general", I call Bigma a "fair weather telezoom", since its highest sharpness and contrast at a large focal length develop at a relative aperture of f=11 and higher (very good at f=13). And certainly not less than f = 9.
But, as you understand, shooting in this way, and even from the hands (more precisely, from the side of the photoboat), is quite difficult in real weather. Therefore, I compared exactly at those relative openings on which I would like to work in real life.