I have the same problem when I go back to my 8700. You have to focus on something solid that is close to where the main point you want is.Holding shutter half way down, slowly move it once it is locked. The moment it finds something brighter in the back ground it will re zoom to that.It does take playing around, and is why I always use manual for macro or with my D70 now.

"The happiness of a man in this life does not consist in the absence but in the mastery of his passions."