kfreels wrote in post #14901452
Just wanted to add this. MFA has nothing to do with the quality of the AF system. It only adjusts the focus to account for where the sensor lies within the spec range. If your new camera doesn't need MFA while the old one did, it's not the AF performance that changed, but simply the camera being at a better place in the spec range for that particular lens or lenses.
This is exactly what I was going to add. Focus accuracy simply means that the camera will repeatedly focus to the same precise point under a given set of circumstances. A highly accurate focus system does not by itself guarantee sharp pictures. If the calibration between the sensors used for focusing and the sensor used to actually capture a photo is off or individual lenses front or rear focuses, a highly accurate focus system would repeatedly yield out of focus pictures. MFA is used to fix the latter problems. Focus accuracy is a separate issue. The amount of MFA required for any given lens, whether it be -20, 0, or +20) is not an indicator of the accuracy of a focus system.
Think of a highly accurate rifle. With the barrel held in the same position aimed at a wall, repeated shots would create a very tight hole pattern. However, that tight pattern may be above, below, left or right of the target on the wall that you were aiming for. That problem has nothing to do with the accuracy of the rifle but rather it is due to a misalignment of the rifle scope. Sighting in the scope on an highly accurate rifle is similar to using MFA with a lens on a camera with a highly accurate focus system.