The best article that I can find was here, here is link to another chart
And the following has been cut from this topic
But if you still have concerns about focusing accuracy, are not sure if it’s user error etc, are dubious about some of the ruler tests worth (as I am), then this method is very simple to use, requires no special equipment, and takes only a minute to do.
Very quick and easy way to check a number of aspects of your focus system repeatably and accurately using no special equipment:
Mount camera on tripod. Use remote release, or self-timer for taking the test shots. If you don’t use a tripod, I think you should consider your results invalid.
Step 1:
Display something predominantly white, with text all over it on your monitor screen. Maximising your Outlook inbox screen works well.
Ensure your camera back is parallel and centred with respect to your screen. Focus on your computer monitor screen manually. Notice that at the point of exact focus, you see a Moire pattern in the viewfinder. (Squiggly interference lines).
Take a picture.
Step 2:
Move the lens out of focus, and this time use AF to onto the screen again, and you should see the moire pattern in your viewfinder.
Take the picture.
Step 3:
Review the images.
That’s it.
Possible Problem Indicators:
If you can see the moire pattern in the viewfinder when manual focusing, but not when Autofocusing, or not in the resultant image on the CF card, that would indicate that there is some kind of focus alignment issue that might warrant further investigation. The moire is always strongest at the point of exact focus, so the AF and MF tests should appear very similar.
Additional test
Instead of using Outlook for the above test, open up FVU and display one of your previous images with the FVU focus point overlay.
Align your camera at the correct distance and position, so that your in-finder focus boxes, overlay those displayed
Now when you review your images, you can also see if the focus boxes in your camera, correlate with those shown in FVU.
The reason I added this step, was that someone on this forum was concerned that their in-camera focus boxes appeared to disagree with those shown in FVU.
Quick, easy and repeatable check of your finder, sensor, and AF alignment.
