Back in the day when the wife were taught to shoot wildlife a good default aperture was F8 as it was usually deep enough to get larger animals in focus especially if the AF point was somewhere on the head. So I used a DOF calculator to calculate the DOF for using a 35mm FF body hooked up to a 600mm lens at aperture F8. I then did a second calculation adding a 1.4TC. Then I did a calculation using a m43 body with a 300mm at F4. Compare the DOF to that of the 35mm 600mm lens without a TC. The last calculation adds a 1.4TC to the m43 300m at F4. Compare the DOF to that of the 35mm 600mm lens with a TC. Moving from 35mm FF bodies, due to the differences in sensor size, to get the same field of view and depth of field, you need half the focal length on the m43 lens and you need double the size of the aperture (i.e. from F8 to F4).