I have focus problem with my Canon EOS 400D Digital. It does not perform well in low light even using a very fast lens like EF 50mm f/1.4. It have occasional focus hunting in low light environment issue. I am not sure why. It just cannot get a good focus lock. And sometime I did not get a good focus. The photo look like focusing the back of my main object. Therefore, I ran some test on its back focus issue. How to test back focus issue? I use the focus test chart from http://focusTestChart.com. It is very useful.
Here are the result I got.
Little bit back focus?
There result is not consistent. Sometime it is fine but some time it is not. It will have back focus issue in when focus more 5m sometime. This is one of the problem I hate. Another one is focus hunting issue. Will try to find out why it has focus hunting soon.