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Old Jul 29, 2007, 4:59 AM   #31
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Now I am more familiar with Canon equipment and the AF cutoff at ~f/6.3 for prosumer bodies is built into the cameras firmware. As soon as a lens/TC combination reports a smaller available max f/number the cameras just shut AF off.
Nikon seems to do the same and I suspect similar is built into the Pentax to prevent the camera from doing endless seeks.
Nope, Tamron et al all say you shouldn't use them below F/4 on 1.4x or 5.6 on 2x, but there s no cut off and glad there isn't.... I'll take slow AF to no shot at all any day.... and with the internal SR, the slow shutter not a real issue either usually. And even under those values in low light, have noticed no real AF speed difference (maybe SLIGHT) on the K!0D even in waining sunset light.

And when light gets real low K10D just fails and says so.... not endless seek.... but retry, almost always still works until things get real dark.... and there is always thatold fashioned thing called MF :idea:
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