Re: Technical Question: Why does Canon lenses autofocus faste...
I think in lens design, like most things in life, there are trade-offs between motor speed and accuracy. If a motor moves quickly, it\'s probably going to overshoot and hunt a little, because it doesn\'t know where it\'s going up front. the PDAF module is saying \"keep going, keep going, keep going, stop there, nope back up a little...\" until it hits the optimum location. Meanwhile there is a piece of software which decides when focus is \"close enough\" and allows the shutter to fire. If I put a greater emphasis on accuracy, it\'s probably better to drive it a little slower, and to be a little more fussy about what is \"close enough\". If you want both fast AND accurate you can get both with a heavier motor, but most users don\'t want a heavy motor, and then parts wear faster so the lens becomes sloppy sooner. To reduce weight and wear, you can use exotic materials, but price goes though the roof.
I don\'t think it\'s a case of anyone not knowing how to make something fast, they just make different choices in how they balance speed, accuracy, cost, weight, and durability. Canon has also deprecated mounts a few times, not just FD to EF, and if you use the old gear you have to use stop down metering. With Nikon can still use lenses from the 50\'s on modern bodies with full functionality because they valued the customers desire for longevity. It\'s all about choices.
Re: Technical Question: Why does Canon lenses autofocus faste...
I think in lens design, like most things in life, there are trade-offs between motor speed and accuracy. If a motor moves quickly, it\'s probably going to overshoot and hunt a little, because it doesn\'t know where it\'s going up front. the PDAF module is saying \"keep going, keep going, keep going, stop there, nope back up a little...\" until it hits the optimum location. Meanwhile there is a piece of software which decides when focus is \"close enough\" and allows the shutter to fire. If I put a greater emphasis on accuracy, it\'s probably better to drive it a little slower, and to be a little more fussy about what is \"close enough\". If you want both fast AND accurate you can get both with a heavier motor, but most people don\'t want a heavy motor, and then parts wear faster so the lens becomes sloppy sooner. To reduce weight and wear, you can use exotic materials, with a price to match.
I don\'t think it\'s a case of anyone not knowing how to make something fast, they just make different choices in how they balance speed, accuracy, cost, weight, and durablility. Canon has also deprecated mounts from FL to FD to EF, and if you use the old gear you have to use stop down metering. With Nikon can still use lenses from the 50\'s on modern gear with full functionality because that\'s where they placed their priority.
May 20, 2016 at 06:55 PM
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