Bohan, thank you for the link. This camera does indeed provide a focal length range in the ball park.
I'll give it a closer look.
Bohan, thanks for sharing! Interesting camera - I do not see a lot with that feature combination.
2Mp Full HD 3x Network PTZ Dome Camera
3.0mm ~ 9.0mm(3x)optical zoom
|Angle of View ||H: 93° ~ 31.7° |
|Closest Focus Distance ||30mm |
Agreed, wide FOV at the expense of zoom range is OKy. This a near field application. 75 degrees to 25 degrees would nice. Similar to an HD fixed dome with remote focus/zoom capability, just add the p/t :) I know, I oversimplify the lens and motion elements. I'm surprised that there hasn't been much call for this. Like John says, most PTZ domes are minimum 10x with an aim to maximize telephoto. The wide end typically is in the neighbourhood of 55 degrees.
How wide do you want? Is 60 degrees good enough? Do you really want 70? etc.
Finding this out systematically is hard because the zoom range (10x, 20x, 30x) does not always coincide with widest zoom ranges. Often, manufacturers care more about max (telephoto) zoom range so give less on the wide side (e.g., a 5 - 100mm zoom range vs a 3 - 60 mm one).
General background: How Far Can a PTZ See? discusses minimum and maximum focal length levels.