Originally posted by Framed Do you think it's possible that missing focus occassionally, be it back focus/front focus whatever, is just a problem that can't be avoided with dSlrs? Yes some of it is user error but I know from my own experience there are times when it is not. It's worse on some lenses than others, but again I am starting to think it's just the nature of dslrs.
Framed - The focus issues being discussed (of the K-5) are not occasional focus misses, but repeatable front focussing issues in dim light. The users who have this issue can reproduce it. There is a very informative thread going on in dp_review, in which Roland has been doing some controlled experiments with graduated ND filters. The issue being discussed is why does K-5 front focus more than K20D in low light. Gordon B Good discusses a hypothesis there.
He says that the + part of the new SAFOX+ autofocus system is programmed to figure out the WB of given light, and make AF adjustments. This was done to improve the AF performance. The problem arises when light levels go down to a level where there is not enough color information available to make the correct WB estimate. Camera then makes the wrong compensation and front focuses by a big margin. And since K20D doesn't have the + system, it does not suffer from the same margin of error.
That discussion and test is still continuing on. I think they are trying to pin down whether the front focus error in k-5 varies with the color of light.
Hope it helps.