HSM vs SDM vs Screw Drive

Started Feb 4, 2014 | Discussions thread
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edspen Regular Member • Posts: 195
HSM vs SDM vs Screw Drive

After playing the what focuses best game with my gear, I pondered this : All the mechanical linkages in screw drives (body motor, gears, couplings, lens couplings, lens gears, etc.) have their individual tolerances when made. These have to add up to focusing inaccuracy. Electrically coupled lenses have less mechanical play, so wouldn't they have more accurate focusing ability ? When the camera sensor shows you're in focus how close is it really ? And, the hunting that some lenses love to do, is that due to loose tolerances ?

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Ed

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