I’ve had a particularly bad experience with a Canon 50mm f/1.4 lens which has led me down the road of trying to understand the lens micro adjustment features on the new high-end Canon Cameras. Below are some references to good information if you are planning on delving into these adjustment. I ended up using the method described in the 3rd reference.
First a reference written December 2008 by
Chuck Westfall in digitaljournalist.org/issue0812/tech-tips.html. See the second question that gets answered.
Here is another one discovered by Ron Matson on photo.net
photo.net/learn/focustest/
(This is the method that I ended up using)
And another which looks quite comprehensive and uses uses a displayed Moire Pattern to set the adjustment
Northlight Images article on Micro Adjustment by Keith Cooper
As an aside, I chalk my experience up to getting a bad copy of the lens combined with my inexperience to realize such before my warranty had expired. If I had dealt with the problem immediately, I would be singing the praises of Canon’s customer service. Since I decided that I was the problem and not Canon and waited 3 years until I got a full frame camera and knew better, I am now stuck with the repair bill. Alas.
iNancy iMages 
Nice work! great website
I just got my 5DmkII, so I’m hoping to solve the same issue with my 50mm f/1.4!
Rick – I strongly suggest that you do some tests with the lens stopped down to f/1.8 or f/2.0 to learn more about the behaviors of this lens. At f/1.4 it is very hard to handle.
Thanks for the heads up, Nancy. I had heard that f/2 was a good setting, so I’m glad that you’re confirming that! I’m doing this this afternoon, before all of the Christmas hubbub starts, so I’ll let you know how it goes.
After testing my 50mm f/1.4 extensively on a couple of different occasions, I came to the conclusion that it was backfocusing by a factor of about 5. This makes sense when I compare it to some of the real world image I have kept around. I tested it at f/2 from ~9 feet away. Now, we’ll see how it holds up with real world shooting. The difference just in the moire pattern method, though, is significant.
Thanks again for posting this! Now I’m doubly glad I upgraded to a 5DmkII.
Just found the adjustment feature on my 5dmkii (only had it 3 months) my 50 1.4 is out by – 10, so glad I upgraded!