How to test camera for focus problems?

I bought a T3i from Adorama in the spring and it has a 1 year warranty through them. i've noticed that I frequently get photos less sharp than those I see produced from other users who have cameras of the same sensor. I had thought originally that it was the cheap lens that came with the camera. however, now i have 3 L lenses and my issue seems consistant.

If I focus/zoom in on an object say 20 feet away and snap a photo i get a nice sharp photo that I can look at 100% view in DPP and see a crisp image and detail. The problem is when I zoom in on something further, say 60 feet away or further. The zoom clicks right into place, but if I enlarge, many times the images look fuzzy and not at all sharp. In fact it will look somewhat soft even at 50% view. It is the same with every lens, the 24-105 (new lens), a used 70-200 2.8 IS. and a 300L. In fact, if I use the 300L and look at a parking lot sign from 60-100' away, when I start to look at it 50% view the lettering doesn't look at all sharp. I often find myself needing to sharpen the photos I get in DPP 200+

So I'm wondering if hwat is happening normal to a degree, and if not how can I test the focus and know for sure if the camera is having a problem. perhaps it is just a function of the low end body/software?

BTW, the problem is not at shutter speeds of 1.10 or anything like that. I'm talking 1/200 1/400 or even faster.

Good sticky just a few lines up from your post

https://photography-on-the.net/forum/showthre​ad.php?t=857871

Duh, ok thanks... now for another question. After reading the testing procedures, what aperatures should I test at?

For example, I want to check my camera with the 24-105, 70-200, and 300. Would it be acceptable to set up a tripod in one location and switch lenses? Or does each lens need to have a difference of distance from the object being focused? Also, what aperature settings would be appropriate to take photos at? I would assume a range from the widest to something like f12 may be enough? How many test shots should someone take?

What would be an appropriate test subject, as far as quality goes? The corner of a building? A curb? car? etc...

mikeinctown wrote in post #15075217
. Would it be acceptable to set up a tripod in one location and switch lenses? Or does each lens need to have a difference of distance from the object being focused?

no less than 50 times the focal length

Be aware that the only certain way to rule out camera movement is to mount it on a tripod for the test. I used to get camera shake so often I always use the "2 over the focal length" rule these days as a minimum when handheld. So I'd be at 1/600s or faster with the 300mm lens.

Lowner wrote in post #15075398
Be aware that the only certain way to rule out camera movement is to mount it on a tripod for the test. I used to get camera shake so often I always use the "2 over the focal length" rule these days as a minimum when handheld. So I'd be at 1/600s or faster with the 300mm lens.

Thanks. I will be using a tripod and will set the timer so my hand is not on the camera for the test.

I will also adhere to the 50x distance, and when I figured out the math, even the 300mm lens would be at about 50' focus distance. I would have gone a bit further anyway.