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Rebel XSi Autofocus Problem

Mike Gendimenico , Jun 03, 2008; 05:32 a.m.

I normally use a 5D for much of my photography, but wanted something smaller and lighter for general travel photography, so I recently picked up an XSi and a Tamron 28-300 VC lens (also have a Rebel XT).

I've noticed that many photos are out of focus when using the 9 point AF. If I use just manual center point auto focus the pictures are much better (AF Mode is set to One Shot & operating in Program Mode). I used it today on some product girls at a trade show and got the same result - slightly out of focus in 9 point mode, good focus in center point mode.

Never had this problem with the Rebl XT or 5D. Any suggestions?

Thanks!

Responses

Giampi . , Jun 03, 2008; 06:26 a.m.

For one thing: have you used that lens with other cameras? By the same token, have you used DIFFERENT lenses with your XSi?

I have an XSi as well an focus is spot on.

Your post is a bit vague and without and actual sample image it's hard to suggest much.

Chris Adams , Jun 03, 2008; 07:41 a.m.

I will almost always pick my focus point and move it around depending on where the subject is. With the 9 point autofocus on there is no telling what the camera is focusing on. If there is something in the backround with a little more contrast it might pick that up. I would stick to using a single point and your results should be better.

Joseph Carey , Jun 03, 2008; 07:49 a.m.

I totally agree with the two follow up's so far. Multi point AF is for very rare instances in my opinion and those long multi purpose small aperture lenses are never going to focus as fast as a normal length lens...

Alan Burhop , Jun 03, 2008; 12:17 p.m.

SInce you have another camera, try the lens on that camera and see if you have the same problem. If you do it is the lens.

Also try a different lens on the XSi and see if you still have the problem.

maybe it is a compatablity issue with the Xsi and the tamron lens.

Brad - , Jun 03, 2008; 12:36 p.m.

I use an XSi and 9 point AF for street photography (like I've been doing for years with my 20D) and have no issues. It's a great cam...

Steve Dunn , Jun 03, 2008; 05:32 p.m.

On what is the camera focusing when you use automatic focus point selection? I don't know if the XTi shows this in the viewfinder; at least some Canon file viewer/converter utilities can show you (EVU can, for instance). Maybe it's choosing a different part of the picture than what you think the subject is.

Mike Gendimenico , Jun 04, 2008; 07:41 a.m.

Unfortunetley, I got the XSi at the last minute, could only take the Tamron lens, and am 6000 miles from home, so haven't had a chance to interchange cameras and lenses for further testing.

The pictures seem to be much better now that I've changed to center point focus at least. I've uploaded comparison photo crops here. Two different subjects, but same shooting and settings except the right image is 9 point AF, left is center point focus.

I do have to say I'm so used to using my 5D that the Rebel is taking some getting used to.


XSi Focus- Left: center point , Right: 9 point

Xingyuan Wang , Dec 08, 2008; 08:03 p.m.

Did you find out anything more -- has the center AF point worked for you?
I think I'm having some front-focus issues on my XSi.

Neat subject, btw. :)

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