Using a zoom for a macro lens has more than distance drawbacks. Image quality can't match that of a fixed focal length zoom. Doesn't Canon have a real macro lens in the same focal length of the Sigma? That's what I would consider.

Canon has a large selection of macro lenses including a compact 50mm f/2.5. But I doubt it would cost as little as Sigma's. However, I would not assume you would obtain significantly less image performance with the Sigma with an APS-C dSLR camera.

I did look at the Canon 50mm Macro Lens, it a little cheaper then the Sigma, I did not consider the Canon because (this may sound silly)it has a 52mm filiter size and the Macro flash that I'll be getting uses a 55mm as the smallest adapter. And some of the reviews said it performed better the the Canon lens. I guess I could use a step up ring to make the flash fit. Maybe a better question might have been is a 50mm Macro lens a good one for Macro shots of flower and the like, I'm not all the big on pictures of insects unless it might be a Bee on the flowers im shooting. I do want a Macro lens were I can be with in say 2 to 9 inchs of the subject.

I personally use the long time standard Canon macro 100MM f/2.8, but I also shoot a full-frame dSLR, the Canon 5D. I do a lot of flower shooting, and have an upcoming article in Shutterbug on one kind of flower photography. As long as you can focus the lens optics really don't make much difference as it did with film photography. If you ever examined a truly raw unsharpened image direct off a camera sensor, you would know why I say that, without in-camera post-exposure sharpening the raw images are extremely soft and low contrast.

I'm not sure just what you are talking about. I will watch for the issue of Sutterbug about shooting flowers. I did find of other posts on other forums and it seams that a 100MM Macro is what most people use. Maybe if I go to a good camrea shop they might let me try out some of the MAcro lens they have in the store to see which one might be good for me. I just subscribed to Shutterbug I'm hoping to can learn more and improve the quality of the pictures I take. Some people say I take great pictures and should sell them, I'm not sure if they are that good.

Your XTi is a typical dSLR with a APS-C size sensor, so being smaller than full-frame (1.5X lens factor) the100m f/2.8, originally made for 35mm film cameras, will have an effective focal length of 150mm. With your XTi camera to get a similar focal length effect, a 70mm macro lens would be needed to be ideal.

The other comment I said about sharpness, instead of spending large amounts of money for premium "sharp" lenses, you would get the same result with a cheaper lens by increasing the in-camera sharpening option available on the LCD menu controls of your camera.