Optical View Finder is not accurate.

[andi]

Hi guys, on the back of my post in this thread - I've run into a problem with my camera that I was hoping you could help me with.

I have a Canon 6D with a 35mm F2 IS. The issue is that what appears to be as in focus in my optical viewfinder is different to what autofocus/live view sees.

1. Camera is setup on a tripod
2. I have an object with text in front of the lens
3. Live view + auto focus brings the text in focus
4. Trigger shutter
5. Review image, text is also in focus

6. Without changing or moving anything, view the object through VF
7. Text appears out of focus, manually focus until text appears in focus through VF
8. Trigger shutter
9. Review image, text is out of focus

10. Without changing or moving anything, view the object through VF
11. Trigger auto focus, text appears out of focus through VF
12. Review image, text is in focus
13. View the object through VF, no dioptre adjustment brings the text into focus

What is confusing is that I can see a perfectly sharp image through the VF, but why is it so misaligned to what LV/autofocus reports?

Thank you in advance.

Cheers,
Andy

- - - Updated - - -

Should also mention that I'm using the standard focus screen, aperture was set to 3.2, shutter speed was set to 1/640.