Instruction: Answer the given question using the supporting document.

Input:
Question: Is this lens compatible with the canon rebel t1i?
Document: I'm using this lens on  Rebel XSi. The XSi records out of focus images routinely so I have no way of knowing if this is a quality lens or not. It's physical quality it great and operates smoothly, the Canon camera is the problem.
Wow am I impressed. I was using the Canon 100-300 zoom on my old Rebel.With my new 30D the 100-300 didn't seem as sharp as it should especially at 300 zoom.This 100-400 lens is a bit heavy, but worth every ounce.It takes clear crisp pictures all the way at 400 zoom.
The up side:This is my first Canon L lens and I have to say I'm really pleased with it. I have it mounted to a Digital Rebel XT and the camera seems to be the weak link in the setup. As far as the lens, the image stabilization is a necessity for hand held shots, the auto-focus is fast and usually accurate. What really impresses me is that I don't have to correct for chromatic aberration... I can't find any at all!
I did a lot of research on the internet for a zoom lens. I wanted a good zoom lens to use for wildlife photography. The Canon 100-400mm lens seems to be the best one out there. So I made the decision to get this lens (which was a hard decision because it is not cheap). I am using the lens on a Canon Rebel XTi. The first few shots I took with the lens did not impress me that much.
Long and short of it? GREAT lens... not so great job on the tension ring mechanism! I would expect better from $1400+ worth of optical hardware.Another Edit: Update March 6, 2013 - I decided to blow a lot of money and get myself a Canon T2i to replace my Rebel XT that shot the picture of the Oyster Catcher in this review. Thus is how I discovered the difference between 8 megapixels and 18.
My camera is the Canon EOS Rebel t5i, so images taken at the extreme telephoto are equivalent to 640mm. My hobby is raptor photography. In particular, the American Bald Eagle. If I could insert a picture here, I would. If zoomed in further than what this lens is capable of on my camera, I would miss the full wingspread on my favorite action - landings. And comparing quality with that of the SX50 hs, almost no comparison. I know, comparing apples to oranges.
I've tried this lens on my Canon Digital Rebel XTI a couple of times in my house since I received it for Christmas. It's been too cold and snowy/rainy to try it outside. From the two photos I took (one of my dog and one of a Christmas wreath) it's not hard to see how incredible and sharp the optics are on this lens. I wanted this lense for outdoor photography rather than indoor shots so I can't attest to how it'll work outside just yet.
Up close with frame filling subjects near wide open aperture the Bokeh is a dream, but shoot at further distances with a cropped sensor camera like a Rebel or Canon 40D/50D etc with branches as a background stopped down so you can see some detail there are weird lines around each item.
The birdies never see it coming, pow.Now, I should add here that my combo is a Canon Digital Rebel XT and of course my new 100mm - 400mm L F5.6 IS USM.The first time I shot at all with this, I was disappointed and worried that I made a big mistake. Yes, I was making a mistake, but not in the purchase, just with what to expect from the lens' behavior compared to the 75-300mm that predeceased it.
I know other people have said the same thing, but it did not become clear to me until I tried to use this lens as a "walk-around" lens. After about 30 minutes it started to become a real problem. And, because I was using this lens on an entry level DSLR (the Canon T1i) it felt as though the lens was not secure in the camera mount.
Answer: Yes; I have both and use them frequently.