what does this ratio meant for?

[PamJazz]

I bought a Nikon P80. I know that it's Lens is ranging from 28 - 486 mm (Wide angelled to Telescopic).
But there is a Specification in the Bottom of my camera, it says:
4.7-84.2 mm 1:2.8-4.5
What does that mean? I undersatnd F stop value is mentioned as 2.8 to 4.5 ,but not clear. Can someone explain me what does that ratio meant for?

[KristoferB]

found this over at Digital Camera Review :

4.7-84.2mm refers to the zoom range of the lens.

2.8-4.5 refers to the aperture of the lens as it changes when the lens is zoomed in or out. It's at f/2.8 zoomed out all the way and at f/4.5 when zoomed in all the way.

Your camera has an equivalent or effective range of 28-486mm, but the actual focal length of the lens is 4.7-84.2mm. Why the difference? It has to do primarily with the size of the sensor: because you camera has a smaller sensor than a frame of 35mm film, the lens's actual focal length has to be shorter to perform like a 28-486mm lens would on a 35mm camera.

We use 35mm-equivalent standards (i.e. 28-486mm) rather than absolute focal lengths for convenience, as a way of "speaking a common language" in a sense. But this isn't the actual focal length of the physical lens on your camera; that's 4.7-84.2mm.

credit: What does this Specification Mean ? - Digital Camera Forums and Discussion