Canon flash spread angle question.

Does anyone know the conversion for Canon 430EX or 580EX from 'mm' zoom on flash to approx angle of spread? In other words if I set the flash at 105mm is that a 20 degree spread? If 24mm is it 80 degrees? I find it easier for me to visual angles. This is for when I'm using the strobe off camera where letting the camera set the zoom may be incorrect for the coverage I'm looking for.

If the flash is off camera, the camera will have no control over the zoom position used. When in auto zoom mode, the flash head will automatically zoom to the 35mm position when it is removed from the camera (in normal mode; in master or slave modes it's 24mm). You can zoom the head manually to whatever position you want, though (not sure about the 430EX, though, since I don't have that flash).

I've never seen the flash zoom positions given in terms of degrees coverage but you can get a pretty good idea by checking the angle of coverage of some lenses. For example, a 35mm lens has an angle of view of 63 degrees. This is the diagonal angle of view, though.

Hey, throw in the fact that the 580 and 430 change the flash angle with respect to the crop factor of the camera, and this can get interesting.

Enjoy! Lon

Maybe but that's irrelevant here since the flash will be used off camera.

Thanks PacAce. Great Idea, using lens data that was easy to search for found a chart listing lens data to angle. Distilled down to:
35 mm 35 mm
Focal Angle
Length of View
in Degrees
20mm 84
24mm 74
28mm 65
35mm 54
44mm 44
50mm 40
55mm 36
58mm 34
85mm 24
105mm 19

Just as a reference when setting up an off camera strobe just trying to lower the 'chimp' factor of setup. Thanks all.