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04-16-2016, 02:27 PM   #1
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Tokina AF 210 II (70-210 mm F 4-5.6): F-- at bottom of zoom range

I just acquired (for next to nothing) a Tokina AF 210 II, which seems to be a nice medium telephoto zoom; it's definitely sharper and more sturdily built than the kit DA 50-200, and I really like the colours. But I'm having a strange problem with the connection to my K5 II: at the very bottom of the zoom range, it doesn't report the aperture to the body correctly. I can't give exact numbers because there's no marking on the lens, but within the last 5 degrees or so of zoom rotation, so maybe between 70 and 80 mm, the lens seems to be sending incorrect or no information. As I zoom out, the minimum aperture the body will allow goes from 5.6 to 4.5, as it should, then jumps back up to 5.6, then the body displays "F--". It never gets to 4.0, and consistently reads F-- at 70mm.

Has anyone seen a similar phenomenon? A fix? (I've tried cleaning the contacts, but that didn't help, and it seems to work perfectly through the rest of the zoom range.)

04-16-2016, 02:35 PM - 1 Like   #2
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If it reports apertures smoothly at other focal lengths, it sounds to me like the contacts which report focal length are missing at one end. The focal length chosen affects the aperture for these variable aperture lenses, and if the control unit doesn't know the one, it can't determine the other. A similar thing happens to my old manual focus Sigma 70-210mm f4-5.6 lens on the A setting; the camera tells me there's an f/4 lens fitted even though the viewfinder has darkened markedly on zoom-out.

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