focus Off in SLR digital cameras

This is not a common problem.

There have been a few cases where a lens will front focus or rear focus with a particular camera.

I don't believe you can fix it yourself.

According to some who have encountered this problem with a new camera, they contacted Canon and they were instructed to send the camera and the lens to Canon.
The problem can be the camera or the lens.
I understand that Canon fixed this for free.

Notice.....It must be a Canon lens, not Sigma, Tamron or other brand.

..........

Front/Back focus means that the lens will autofocus slightly in front or behind the target focus point.

................

You can set up your own test quite easily.

In a room with normal lighting.
Lay a yardstick on the floor.
Set your camera to center focus and autofocus
Put your camera on a tripod, near the one inch end of the yardstick.
Have the tripod high enough that you are looking down on the yardstick at a 45 degree angle.
You will be looking down the length of the yardstick.
Center focus on the 18 inch marking on the yardstick, by pressing the shutter button halfway down.
Press the button the rest of the way down to take the photo.

Examine the photo on a computer monitor.

The sharpest focus should be at the 18 inch marking on the yardstick. If the sharpest focus is at the 16 inch marking, your camera or lens is front focusing.

...
..
.

1. You may choose any focusing spot ( one of 9 spot showing on your focusing screen ). Therefore, you know where to focus and recompose your picture. It helps me when shooting a very bright back-ground picture.

2. Use a manual focus to make sure that the picture is at your required focus. Recheck the focus right after shooting, zoom-in to make sure it's the correct focusing area.