Motorized bodies and AF vs. AF-S lenses

[robert_n_moz]

<p>Hi everybody:<br>

This is a purely technical question that arose as my friend and I were discussing autofocus speed.<br>

AF-type lenses rely solely on the integrated motor of the body it is attached to to achieve automatic focus (right?, please correct me if I'm wrong). Since AF-S-type lenses have their own motor, which one of the two motors has precedence? Does one completely concede the AF process to the other, or do they “collaborate”? If the latter, in which way, and if gain there is, to which extent?<br>

Actually, beyond satisfying our own curiosity, it may help him decide on a zoom for shooting indoor sports, as he found its AF-D 80-200mm f/2.8 (two-ring model)-D90 combination a tad slow.<br>

Thanks!...<br>

Rob</p>

[ShunCheung]

<p>All AF-S lenses (and their predecessor AF-I lenses) have no mechanical connection to the AF motor shaft on the body. Therefore, AF-S lenses cannot use the camera body's AF motor (if there is one).</p>

[georges_pelpel]

<p>In regards to the AF-D 80-200, its AF speed will be different depending on the body it is used on. The D90 has a slower AF motor than say the D300.<br>

The body might not make a huge difference when using small lenses but with a large, heavy one such as the 80-200/2.8D the difference is noticeable.</p>

[frank_skomial]

<p>There is no lens that would incorporate AF and AF-S in the lens, in the same body. So, there is no precedence.<br /> Nothing to concede.</p>

<p>Generally AF-S lenses should be faster than AF, but there are cases with camera/lens combination that this is just opposite.</p>

<p>Each lens/camera focusing speed needs to be evaluated individually. Generalizations could lead to wrong conclusions.</p>

<p> </p>

[robert_n_moz]

<p>Thanks a lot for your pertinent remarks.<br>

It was indeed easy to make assumptions, and when you assume...(!)</p>

[jim_momary]

<p>Case in point, with a Nikkor 50mm 1.8 AF lens ...</p>

<p>on my Nikon F4s, the lens as it focuses, sort of just burps and jumps to the correct point,</p>

<p>whereas on my N90 (which isn't a slouch by any stretch) it takes a noticeable bit longer and seems to have a tad bit of hunting.</p>

<p>May the torque be with you.</p>

[Andrew Garrard]

<p>Some AF-S lenses can benefit in performance from a higher-end body with a higher battery voltage that allows the lens to be driven harder; the single digit D-series cameras are in this category, as are some of the battery grips. The effect is probably minor compared with the advances in AF programming between camera generations. Bigger bodies also often have more powerful drive motors and, as suggested, this affects the performance of screw-drive lenses; how much depends on the lens. The 80-200 is a heavy think to focus (although not as bad as the one-ring mk 1), and I'm sure you'd see a significant difference between a D90 and a D4.<br />

<br />

The 70-200 f/2.8 AF-S lenses are appreciably faster to focus than the 80-200 AF-D; I've heard that the difference between the two-ring 80-200 AF-D and the AF-S version isn't all that great. I've seen this on a D700 and D800; I'd expect, if anything, more of a performance difference on a D90 because of the weaker screw drive motor. I can't vouch for that combination from personal experience, though.</p>