Why is there a different field of view for different makers of scopes at the same magnfication? In some cases the difference is very small and in otheres it's rather large. For example S&B 3-12*56 [email protected] [email protected] vs. Zeiss 3-12*56 [email protected] [email protected] or NF 5.5-22 [email protected] vs. bush 3200 5.5-15 [email protected]