aceO07- I am not saying the Canon "L" lenses are for everyone and you have to decide what kind of shooting you want to do. I currently have the following lenses for my XT:
Sigma 18-125
Sigma 55-200
Canon 18-55 Kit lens
Canon 50 F1.4
Canon 70-200 L F2.8
Canon 100-400 L IS USM
Canon 1.4X TC (teleconverter)
The lens I use the most is the Sigam 18-125 as it is my walking around lens. I quickly ruled out the Canon 17-40 as it was overpriced and the actual quality wasn't much better than the Sigma 18-125. The 18-125 has totally replaced the stock kit lens (which isn't terrible). The Sigma gives me good wideangle (WA) and a decent zoom which the Canon 17-40 didn't. For an everyday lens I also considered the Tamron 28-75 which is an excellent lens but as mentioned is heavy but worst for me is the WA wasn't very useful for me indoors like at a museum or trying to get a big group of people in the shot. The plus Tamron is that a fast lens and has excellent quality.
Unfortunately the laws of physics mean that on the sensor the size of most of the Canon/Minolta etc. dSLR that to be "fast" means you have to gather a lot of light so the lens diameter has to be bigger. Bigger-more glass=heavier. My 70-200 2.8 is a perfect example of a not a lightweight lens but I don't think it is terrible. What I have noticed with one the lenses (about 3lbs) is that the LENS will support the camera and not the camera supporting the lens. You have to adapt a little but with the XT it feels easier to do this than with the 300D (original DReb).
In lenses you truly get what you pay for but you can easily overpay. This is very true of some of the Canon lenses. I am not a lens snob by any means but I did spend some serious cash to buy the lenses I have BUT I carefully weighed my purchases before I bought the lenses I did. Out of the lenses I have the to Canon L lenses I have will sell in about 5 minutes if you put them up for sale because they are that well respected in the photo world and that popular.
The 70-200 2.8 is an amazing indoor sport lens. Take that into your local gym or arena and it will take stunning photos. The 100-400 L with IS (image stabilization) is amazing outdoors with decent light. They are each on my camera about 15% of the time and the Sigma 18-125 is there about 60%. One lens to consider for someone starting out is the Canon 50mm 1.8 AKA the "Plastic Fantastic" as it is available for about $70 and is very fast (great indoors lens and for portraits) and has decent bokeh. I bought the 50 1.4 because I wanted a slightly faster lens that was metal construction.
As I mentioned earlier the stock kit lens is pretty decent but it does have a very limited zoom. The top of range the 55mm is actually is about the equivalent of a 88mm zoom on a normal 35mm. The WA aspect of the lens isn?t bad and it?s not too heavy but 88mm isn?t much of a zoom nor is the lens very fast.
I bought the Sigma 55-200 not because it was a great lens but when I don?t want to put on of my L lenses at risk such as in a dangerous area (risk of theft) or a less than ideal climate such as a lot of dust, dirt, sand, etc. It isn?t a bad lens at all and has good reach. Not very fast but I picked it up at a great price and I find I use it enough to justify keeping it.
aceO07 ? DPReview is a good sight but I can suggest a MUCH better site for people who want to take this hobby seriously or even for pros. I suggest going to
www.FredMiranda.com (AKA FM) if you want a great site with a GREAT forum to buy and sell equipment or lenses. If you put a 70-200 2.8 L lens up for sale here it will typically sell faster than it would take a drunk blonde to find a date at a frat house!
At the FM website it is sort of like AT but for camera geeks of which I am proud to be one. There are people who spent more on 1 lens than probably some of you have spent on your cars. Contrary to what many people think the cameras are NOT the expensive part; then lenses ARE!!! But if you buy good lenses you can easily resell them or use them on your next camera if you keep a similar style of fitment.
If you try different lenses you will actually start to see the variation in lenses. There can be wide differences in the actual quality of the shots the lenses take. You can actually see how the lens affects the contrast and the color of your shots not to mention the resolving power of the lens are how the image may soften up from the center. After a while you may even start to notice the CA (chromatic aberration) of the lens which is evidenced by purple fringing on the sharp borders of object.
For example look at the tops of waves and see if you see purple there when looking closely at the photo OR look at a tree limb where the sun is coming from the back. After a while you will start to see vignetting of the lens where the image has a noticeable drop-off in the brightness near the corners. What you ultimately want is a lens with no CA or vignetting and with sharp corner to corner focusing and with good contrast. You can achieve better sharpness by decreasing the aperture (ie higher f/stop) but then you can?t use as fast a shutter speed. So if you start with a faster lens you have more flexibility.
The problem with only having one lens is it is like playing golf with one club. Even if you have a ?zoom? club you are still going to make sacrifices in some area OR you will pay a lot more $$$. In the real world it is impractical to have all 80+ Canon lens unless this is your profession AND you have REALLY deep pockets!
If you could only buy just 1 lens, I?d suggest the Sigma 18-125 as it is a good WA lens and has a decent zoom AND it doesn?t cost a wad of cash. You can pick it up in the mid $200 range and stopped down a bit it is pretty sharp. Couple that with it isn?t too big or heavy and you have a great all around lens. Other options in this price range don?t have much wide angle coverage or have very anemic zooms. A zoom is a compromise by its nature but very useful. What good is have the best lens in the world if you don?t have it on your camera when you need it!