Dennis ..... It looks like I was writing my note when you posted.
Here is how the numbers compare on the SF 10X42 and the Swaro SV EL 10X50 when calculated using the same method.
Swaro 10X50:
FOV at 1,000 per Swaro is 345 feet
Calculated Angle of View is 345 feet divided by 52.5 feet, giving a 6.6 (rounded) degee viewing angle.
Calculated Apparent Field of View using the simple method is 10 power times 6.6* view angle giving 66 degrees.
Zeis 10X42 SF:
FOV at 1,000 per Zeiss is 360 feet
Calculated Angle of View is 360 feet divided by 52.5 feet, giving a 6.9 (rounded) degee viewing angle.
Calculated Apparent Field of View using the simple method is 10 power times 6.9* view angle giving 69 degrees.
This is a 69 degree AFOV for the SF and 66 degree AFOV for the SV using the simple method.
Follow-up on seeing the last post from Dennis:
Dennis, note that the Swaro USA site lists a 62 degree AFOV for the SV EL 10X50. It looks like that is a more precise number (as also used by Zeiss England) than the 66 degrees using the simple method. If you were to back into the Angle of View like it appears Zeiss USA did, then the Swaro Angle of View would be 6.2 degrees, not 6.6 degrees.
http://www.swarovskioptik.com/nature/el-50-c21011003/el-10x50-p5222918
Method 1 comparison AFOV as stated on the web sites:
Zeiss SF AFOV - 65 degrees, Swaro SV - 62 degrees.
Method 2 comparison AFOV using the simple calculation:
Zeiss SF AFOV - 69 degrees, Swaro SV - 66 degrees.