Distance of ZOOM lenses on a PTZ camera

[rory 0]

anyone know what a 25X PTZ Camera's furthest zoom distance is in feet please?

 

tanks

Rory

[cctvfan 0]

My understanding is the zoom ratio iteslf (i.e. 25x or 18x) won't tell.

 

For example, a 25x motorized zoom lens' focal length may vary between 3.5mm (wide) and 87.5mm (tele). But a different lens that varies between 4.75mm and 118.75mm is still considered 25x !

 

So you need to first figure out the absolute focal length (at the telephoto end) of your PTZ, i.e. whether its 87.5mm or 118.75mm or sth else. Then the standard lens calculator should tell you what object size (W/H) can be covered at any given distance (of course another input to the calculator is the CCD format, i.e. 1/3 or 1/4, or even 1/2 given the high-end stuff you're using most of the time

[Cooperman 0]

Quite right cctvfan,

 

Just to clarify one point though,

 

Most manufacturers incorrectly use 25x to imply the zoom ratio of the lens.

In practice, 25:1 is the correct way to display a zoom ratio (i.e. longest to shortest focal length), and 25x would normally imply 25 times magnification, when compared to a normal standard focal length lens.

 

So for example, an 8 - 120 mm zoom is a 15:1 optic,

which provides a maximum magnification of 10x on 1/2", and 15x on 1/3".

[dusan 0]

Quite right cctvfan,

 

Just to clarify one point though,

 

Most manufacturers incorrectly use 25x to imply the zoom ratio of the lens.

In practice, 25:1 is the correct way to display a zoom ratio (i.e. longest to shortest focal length), and 25x would normally imply 25 times magnification, when compared to a normal standard focal length lens.

 

So for example, an 8 - 120 mm zoom is a 15:1 optic,

which provides a maximum magnification of 10x on 1/2", and 15x on 1/3".

 

hi

yes and that is why idiots are manufacturing new 1/6" ccd sensors

so can use same lens and call a camera 27x zoom , as you go down

on ccd size you loose light sensitivity and resolution

 

dusan