i am a beginner to photography and i brought rebel xti four months back along with 50mm f 1.8, with no kit lens. slowly realized the limitations of 50mm..they were just good for portraits but if i wanted to take landscape its just impossible. if i made my friends stand in front of a beautiful landscape either i could focus only on the person standing in front or could focus on the landscape behind..then two months back i brought sigma 18-200 with os and realized on the very same day that the outcome was not clear even though the colour and contrast were all fine. so i gave it back very soon. right now i am looking for a lens that meets my following needs 1)has to be under 600$ max 2) clear and crisp image must! 3) ready to buy canon, because i live in ny i have a fascination for taking skyline shots in the daylight and night so after taking the pictures, when i zoom it on my laptop, if the details of the faraway buildings comes out clear then i would love it..like the image below (just for reference , found it on the net). http://farm1.static.flickr.com/48/145844430_526cce201f_b.jpg so all in all i need a lens that takes far away pics clearly that includes cityscape , should do good for landscapes as i travel a lot to national parks and stuff and take good portraits too.