Well folks, I have some good news and not so good news.
I received a new K-5 yesterday (serial # 4033…) and have compared the performance to my K-5 camera (serial # 390…).
The good news is that the performance is of both cameras behaved about the same in dim lit conditions. Perhaps I can conclude my camera is performing within factory specs. Also, I noticed that the image in my viewfinder seems sharper when the image is in focus. But that is unrelated to the ff issue
The bad news is that they both are exhibiting the front focus problem. It doesn’t even have to seem to be that dim for this problem to occur. Also, it occurs when there is still too much light to trigger the focus assist light. It seems that the AF (without AF assist light) starts getting unreliable under 2 EV.
I will try and do a controlled test tonight that might give a little bit more information what is going on.
I also finally found this product:
Photography Lights: Digital Photography and Camcorder Lighting Accessories
It was mentioned in this forum a while back and it could help in some situations (though it might be annoying to some people). Or stop down and make use of the low ISO capabilities of the camera. I hate to sell off all my Pentax gear and switch brands, but these issues with basic features are really getting annoying. I got the impression that Nikon addressed the focus problem on their D7000 and the Canon 5MII was more of a quality control problem. In any case I will keep an eye out on future replacements of the Canon 7D and Nikon D300s.
For those who want to compute the EV of a certain exposure setting, here is the Excel formula:
=LOG(A2^2/B2,2)+LOG(100/C2,2)
A2 = Aperture
B2 = Shutter time
C2 = ISO
This is different from LV (light value) that is nicely explained in:
What are EV and LV © 2005 KenRockwell.com
Although the nice thing about using EV is that to get a proper exposure, the light loss of the lens itself is compensated for.