Originally posted by fletcherkane First, You need have the camera set to Manual focus. .........The LCD should have a screen asking you to enter the focal length of the lens. Select the right focal length, and you should be good to go.
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Good luck.
This is good advice, but I thought I'd add something since I was fiddling around with my K100d and some "A" lenses today. I forgot to switch the AF/MF switch to MF when adding a Pentax SMC-A 28mm lens, and the camera still asked for the focal length after I turned the camera back on. I seem to forget to switch to MF a lot and don't notice anything amiss until I try to focus, then it dawns on me.......