Found this thread because I also came across the problem of the K20D reporting the Sigma 120-400 as a 70-200, even though it will report correctly what focal length I used, so I get a laugh out of my Sigma 70-20 being able to go all the way out to 400mm. I used Tim Jackson's v.2.00 a focus chart from 2004 (on a cloudy day) and focus for the recently acquired Sigma 120-400 seemed fine at at different focal lengths. I'll retest again on a more sunny day. The softness was readily apparent at the max aperture when zoomed to 400, with a significant improvement at f8, by the way.
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