I am just wondering if anyone would know how to calculate (or if you could calc for me ) the horizontal AOV (and maybe also the diagonal) for a panasonic 20mm lens if shooting in 1:1/6:6/square format.

From wikipedia, the formula is 2 * arctan ( sensor size / 2 * focal length) (that's in radians also). The m4/3 total diagonal is 21.6mm, but cropped to 1:1, it's just sqrt(13^2 + 13^2) = 18.4mm. So normally we get a diagonal AoV of 56.7 degrees, and 36 degrees vertical, and so 36 degrees is also the horizontal angle for a square crop, and for the diagonal for the square crop we get 49.4 degrees.

Thanks. Stupid me! The new horizontal aov would the same as the current vertical. Duh! Thanks so much