Following up on what Les posted:
4 1/2 x 6 1/2 is approximately 50 Degrees
6 x 9 - 36 Degrees
6 x 12 - 26 Degrees
6 x 16 - 19 Degrees
6 x 22 - Sorry, I'm forgetting but very close to Strand's 2112, not their 2212 but their 2112.
While not strictly correct, a rule of thumb for the 6 x __ nomenclature is to treat the first number as the diameter of the field and the second number as the distance from the fixture. So a 6 x 16 produces a 6' circle at 16' from the fixture.
While not strictly correct, a rule of thumb for the 6 x __ nomenclature is to treat the first number as the diameter of the field and the second number as the distance from the fixture. So a 6 x 16 produces a 6' circle at 16' from the fixture.
While not strictly correct, a rule of thumb for the 6 x __ nomenclature is to treat the first number as the diameter of the field and the second number as the distance from the fixture. So a 6 x 16 produces a 6' circle at 16' from the fixture.
According to Michael Zinman's Pocket LD for iPhone/Pod:
360Q-4.5 x 6.5 at 6.5' throw: Beam Dia 2'-7", Field Dia 6'-5"
360Q-6 x 9 at 9' throw: Beam Dia 2'-7", Field Dia 5'-12" (!?)
360Q-6 x 12 at 12' throw: Beam Dia 2'-5", Field Dia 5'-7"
360Q-6 x 16 at 16' throw: Beam Dia 2'-4", Field Dia 5'-6"
360Q-6 x 22 at 22' throw: Beam Dia 3'-2", Field Dia 4'-4".
Works pretty good for 6x9, 6x12, 6x16. Not so much for the 4.5x6.5 and 6x22. Still, myth proven.