Hi everyone,

I'm going to move from a Nikon D90 to a Canon 7D in a month or so, so I am pricing up my options. I'd rather get something I can grow into, rather than wishing I got a better lens earlier on. After a good walkaround lens, nothing specialty.

Here are a couple I am looking at:

Canon EF 28-135mm f3.5-5.6 IS USM Lens - http://www.dwidigitalcameras.com.au/...p?idProduct=48

Canon EF 24-105mm f/4L IS USM Lens - http://www.dwidigitalcameras.com.au/...?idProduct=489

When a lens says f/4 - can it do anything outside of this, like f/5.6? I am getting confused because some lenses detail the window of f/range.

I tried Googling to see whether there is a comparison to show the quality difference between L and regular lenses, but couldn't find anything. Did a lot of reading about weather-resistant bodies and the motors, but nothing about the quality of glass. But that's what I've heard L series lenses are known for...

Anyone had any experience with these lenses? What's your opinion on them?

Thanks in advance.