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Old Dec 29, 2009, 11:24 PM   #1
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Default AF-S vs In body focus motor speed

Which is faster?
If both are present (for example AF-S on a D90), which motor will AF?
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Old Dec 29, 2009, 11:58 PM   #2
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If the lens has a motor, it won't use the camera's motor.
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Old Jan 15, 2010, 8:19 PM   #3
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If the lens has a motor, it won't use the camera's motor.
Thanks. Is AF-S faster than the in body motor?
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Old Jan 15, 2010, 8:48 PM   #4
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Originally Posted by NothingRare View Post
Is AF-S faster than the in body motor?
Actually, there's no way to test that.
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Old Jan 15, 2010, 8:53 PM   #5
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I would suspect the larger motor weather in the lens or the body to be faster, as it will be a stronger and thus AF the lens faster. But I can be completely wrong.
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Old Jan 16, 2010, 8:09 AM   #6
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Originally Posted by NothingRare View Post
Thanks. Is AF-S faster than the in body motor?
You'd have to take performance on a body by body and lens by lens basis.

In some cases, the camera body's focus motor may be better with a similar lens design. For example, I saw a test comparing Autofocus Speed on the D300 using the AF Nikkor 50mm f/1.4 (screw drive via the camera body's focus motor) versus the new Nikkor 50mm f/1.4 AF-S (Silent Wave Motor focusing) lens.

The older 50mm f/1.4 using the camera body's focus motor was faster (although there wasn't a lot of difference) on a D300 body.

But, with a different camera body, the results may have been the opposite, as the speed and torque available from the camera's AF motor comes into the equation, as does the way a lens is geared and more.

As TCav says, there's no way to test that with the same lens, because they're designed to work only one way or the other. IOW, you'd have to look at each lens on a case by case basis to determine the one with faster focusing, and the camera body is also part of that equation.
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Old Jan 16, 2010, 9:43 AM   #7
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Different lenses also behave differently on the same body focusing motor depending on the lens gearing...
For example on my tokina 16-50 f/2.8: This lens can focus from 1ft to infinity in less than 1/4 turn of the focus ring, so this lens just snaps into focus with its screw drive faster than any HSM, AF-S or SSM than I ever used on a D300
On the other hand I tried a screw drive macro the other day and it's so slow on the same D300 body

-> You can say the same about AF-s on two different lens type... regardless of the body
i.e. don't just assume with AF-s a lens will automatically be faster either
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Old Jan 16, 2010, 10:07 AM   #8
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Yep... For example, one thing Sony dSLR users noticed with the Sony 18-250mm versus Tamron 18-250mm lenses was that Sony decided to use different gearing with it's lens (even though the optical designs appear to be the same with both lenses). From reports I've seen from Sony users, accuracy is still fine (despite the tighter gearing).

See this page of a review about it.

http://www.alphamountworld.com/revie...iew?page=0%2C1

Here's a quote:

Quote:
6. Auto focus speed and accuracy- One of the best upgrades this lens has over the Tamron is the AF speed. The simplest technical explanation is that the Tamron takes 21 screw turns to focus from one end of the focus plane to the other, whereas the Sony only takes 12. Just about half! Mated with the A700, this lens has no issues keeping up AF at any focal length, and zips into focus very prompt. Tracking is even faster and this lens has no issues keeping up with moving objects such as birds or cars, or kids. This is a welcome upgrade in my opinion over the Tamron and makes the extra $50.00 well spent.
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