L series walk around lens

[snap]

I bought a Canon Rebel XT several weeks ago. The kit lens 18-55mm came with it, almost at a give away price. The picutures are OK, and much better than my previous point and shoot, of course. I am looking for a better walk around lense. Sigma seems to be a popular choice. I am also thinking about the Canon EF 24-105mm f/4L IS USM. Yes, it is expensive. As a novice I don't know how to evaluate lense quality, as photos I have seen on various web sites and magazines are taken under a variety of settings with a variety of lenses. My question is: Is the Canon 4L that much superior to the Sigma (of about the same focal lenght plus or minus) for the price difference? Under what circumstances is there a noticable difference between the lenses?

[coldrain]

What Sigma are you referring to? The 24-105mm L is on the moment not available because there is a little problem that Canon is fixing first.

If you refer to the 18-125mm Sigma, the Sigma has a wider angle and that may be nice for walk around lens. But the optics of the 24-105 are very much better, resulting in better colours, better contrast, sharper photos and nicer depth of field and bokeh. There are other lenses to consider that give better quality than the 18-125, and cost less than the 24-105 L.

Sigma 18-50 f2.8 EX DC,
Tamron 17-35 f2.8-4,
Tamron 28-75 f2.8,
Canon 28-135 IS,
Canon 17-40 f4 L for example.

Decide first what focal lengths you want to cover, and then what lens/lens combinations are possible. And do not forget to see if there are prime lenses that may be interesting too...

In this case you get what you pay for, also the law of diminishing returns applies. The more expensive lenses get, the smaller differences get too. It is upto the individual to decide if it is worth it.

[Rhys]

I went for the Tamron 17-35 and 28-75. I'm looking toward the Sigma 70-200 f2.8 as well.

[ReF]

if you are willing to carry two lenses instead of one you'll give yourself much more flexibility. carrying just one lens around is VERY restricting on many different levels IMO.

[cdifoto]

if you are willing to carry two lenses instead of one you'll give yourself much more flexibility. carrying just one lens around is VERY restricting on many different levels IMO.

Better yet, get 2 bodies and 2 lenses. Sling one over your left shoulder and the other over your right shoulder...assuming you have 2 shoulders. If not, get a prosthetic. :D