tc-16a on N90s

I'm going to use a TC-16a on my Nikon N90s to see if it really does AF my old manual lenses. Does anyone

have experience with this device? Does it degrade optical qualities? Do lenses have to be a certain speed to

work with it? Also, I assume minimum focusing distance changes a lot with the TC on. True?

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<p>Do lenses have to be a certain speed to work with it?</p>

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<p>Up to 300mm, f/2.8 and faster. "Limited" AF capability - one needs to manual focus to get close and let AF do the rest. See here for more info: http://www.sassmannshausen.eu/lenses-html/other-equipment/</p>

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<p>Also, I assume minimum focusing distance changes a lot with the TC on. True?</p>

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<p>No, focusing distance is unaffected.</p>

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<p>Does it degrade optical qualities?</p>

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<p>Some report vignetting and soft corners - my experience too. Like every TC, it affects optical quality - the extent of which depends on the lens being used. I turns an excellent one into a very good one, a very good one into a good one and a good one into something mediocre.</p>

<p> </p>

<p>The 2X teleconverter I have has a 2:1 gear reduction on the focus coupling, for those lenses that use that for focusing. Using lenses with built-in motors, there is no reduction, and the ones I have tried have a hard time, with the additional reduction in aperture also making it harder.</p>

<p>Using a 1.4X TC, I find that AF usually does work.</p>

<p>The TC takes only the center part of the lens image. That magnifies lens imperfections. Note, though, that for a lens with poor edge performance, it might improve or at least not get worse. </p>

<p>Mostly, you should use TCs when performance is less important than getting the shot at all. </p>