Hey there, no question is too stupid to ask!
as others have said:
"optical zoom" Is something that is used to market point and shoot digital cameras. It refers to a ratio of the shortest focal length and the longest focal length, for example if a digicam that goes from 20-200mm would have a 10x optical zoom. To convert your lens' focal length into optical zoom you would need to compare it to the focal length of a specific camera.
So if your friend has a digicam with 10x optical zoom that goes out to 225mm, your 450mm equivalent lens has 20x optical zoom.
In other words, forget about optical zoom, just think in focal length.
Thanks, I'm used to motoring forums where you get flamed for asking basic questions!
Am I correct in thinking 300mm on a 70-300 lens will look the same as 300mm on a 18-300 lens? The problem is I am after a budget dslr and an extra lens mainly for motorsport, where I will be stood at the edge of the track and need to get close up to the cars, my current 5x optical zoom compact doesn't get close enough so i want to buy a lens that gets me closer than that!