A true macro can cost quite a bit.

As for the whole crisp and sharp thing, thats really up to you, and to some extent the settings in the camera. That kit lens can actually get pretty sharp zoomed to about the middle (not all the way in and not all the way out) and the aperture somewhere in the f/8 to f/16 range. Set your camera to Av, roll the wheel behind the shutter button until you set your aperture to 11 (just a number in the middle), press the shutter button half way and see what speed it gives you. If its less than 1/50th you will need to increases your ISO, just increase one step at a time as the higher ISO's give a lot of noise. Find a happy medium and shoot.

The first lens i recomend is the http://www.bhphotovideo.com/c/product/169267-USA/Canon_6473A003_75_300mm_f_4_0_5_6_III_Autofocus.html it's a bigger zoom than your kit lens.
The second lens I suggest is the http://www.bhphotovideo.com/c/product/12142-USA/Canon_2514A002_Normal_EF_50mm_f_1_8.html It doesnt zoom at all, but it has an aperture of f/1.8 which is awesome with low light situations. It also is a bit sharper than your kit lens. It does these things better because it just has to do them at 50mm and not a whole zoom range.

For Macro or close up stuff you could just get one of these http://www.bhphotovideo.com/bnh/controller/home?O=search&A=search&Q=&sb=bs%2Cupper%28ds%29&sq=asc&ac=&bsi=&bhs=t&shs=&ci=158&at=Magnification_Set&at=Size_58mm&basicSubmit=Submit+Query it screws onto your lens just like a filter (you should always have a UV or sky filter on your lens more for physical protection than anything else). They make higher magnification ones as well.
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Im just new to DSLR photography. Initially I was contemplating on buying either Canon's Rebel XTi or EOS 40D. I end up buying the EOS 40D which comes as a kit together with EF-S 17-85mm F4-5.6 IS USM zoom lens. Based on what I read and learned from the dealer, you could actually use this lens for general photography and macros.
With the camera I bought it with, the price of the lens came out to $350 compared to a retail price of $649.00 if you will buy the zoom lens alone. The dealer said that this lens could also fit into the Rebel XTi as he was initially recommending me to buy the XTi and this particular lens. I would say it will also fit your Rebel XT. Overall, I would say that there are lots of good and quality lenses out there (especially Canon), but the sure thing is, it will really depend on your budget. I would say try to invest with a little bit pricey lens (like the one mentioned above) with features like image stability as the XTi does not have built in image stability feature and Im not sure if the XT model does. This will help you getting clearer and crispier photos especially when you're doing macros. In macro photography, experts also recommend using a small tripod, to prevent from getting blurs in your photos. Handholding your camera may cause slight motions which could blur the shot even if you have lens with image satbility feature. Hope this helps.
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