Multiplier not Autofocussing

I have a Kenko P-AF 1.4x MC4 multiplier that has developed a bizarre problem when paired with my DA*16-50. It simply will not auto-focus - the camera display rapidly 'flickers' between MF & AF but the lens will not autofocus. I have tried cleaning the contacts on both the lens and the multiplier but the problem still occurs.

However, when I use it with any other of my fast lenses it works fine, i.e. it auto-focuses in whichever mode I have selected.

Any suggestions/thoughts?

Phil

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K-5iiS; K-r; ME Super; ME; DA* 16-50 f2.8; DA 18-135 WR; DA 55-300 WR; HD DA 15mm F4 ED AL Limited; FA 50mm f1.4; A50mm f1.7; DAL 18-55mm; M40mm f2.8; + assorted non-Pentax lenses

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I have never got any teleconverter, bar the Pentax 1.4x WR, to autofocus reliably with SDM on Pentax bodies. I have the Kenko 1.5x and although it has the required contacts for SDM it hunts back and forward and rarely locks focus.

Interestingly it used to work a lot better until Pentax issued a firmware update (some time ago) when they released their own 1.4x WR converter.

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Mike

Thanks for pointing me in the right direction. I've tried it with a couple of slower screw drive lenses and it works fine.

it's just not happy on the SDM ones.

Phil

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K-5iiS; K-r; ME Super; ME; DA* 16-50 f2.8; DA 18-135 WR; DA 55-300 WR; HD DA 15mm F4 ED AL Limited; FA 50mm f1.4; A50mm f1.7; DAL 18-55mm; M40mm f2.8; + assorted non-Pentax lenses

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Yes, doesn't work well with Sigma HSM either.

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They won't play with the PLM 55-300 either.

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Both the *istDS and the K5 are incurably addicted to old glass

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