Index

Focus Specifications (close focus distances are listed under optical specifications)

	Nikon	Tokina	Sigma	Tamron
Auto Focus on D40/D40x?	Yes	NO, manual only	Yes	NO, manual only
AF Mode *	AF-S	Traditional w/clutch	AF-S	Traditional
AF/MF switch	M/A - M	Push-pull clutch.	None.	None.
Focus Ring rotates in AF?	No	No	No	Yes
Focus Direction	Standard	Standard	BACKWARDS	Standard
Manual Focus Gearing	Reduction	Direct	Reduction	Direct
Focus Ring Rotation	1/5 turn	1/4 turn	1/3 turn backwards	1/4 turn
What Moves in MF?	Internal elements rotate.	Internal elements move but do not rotate.	Internal elements rotate.	Internal elements rotate.

* Traditional is a motor in your camera driving the lens through a slotted connection on the lens mount. AF-S is a motor in the lens driven by electronics in your camera. Sigma calls their AF-S "HSM"

Focus Performance

	Nikon	Tokina	Sigma	Tamron
Ease of use	Excellent	Excellent	OK. Requires a lot of rotation for manual focus. Side AF sensors may not work!	OK
AF Speed	Fast	Fast. 1 turn of the AF screw goes from infinity to 3.5 feet.	Medium	S - L - O - W ! 1 turn of the AF screw goes from infinity to only 15 feet. The Tamron requires the camera's motor to spin 3.5 times as far to focus as the Tokina does!
What Moves in AF?	Nothing moves externally. Internal elements move forward and back.	Nothing moves externally. Internal elements move forward and back.	Nothing moves externally. Internal elements move forward and back.	External focus ring rotates. Keep your hands away from it of you can damage your camera! Internal elements rotate. No external elements move
AF Noise?	Almost none	Camera's AF Motor. You can hear it but it's over almost instantly.	Quiet with a little bit of squeaking	Noisy and slow.
Focus Ring rotates in AF?	No.	No.	No.	Yes, beware!
Manual Focus feel	Smooth, damped and mostly dry	Smooth, solid and and greased	Smooth and greased. Long throw.	Fast and dry, just like Nikon's first AF lenses 20 years ago. The AF gears are noisy since they spin fast as it focuses.
Manual Focus Gearing	Reduction	Direct	Reduction	Direct
Focus Direction	Standard	Standard	BACKWARDS	Standard
Focus Ring Rotation	1/5 turn	1/4 turn	1/3 turn backwards	1/4 turn
What Moves in MF?	Internal elements rotate.	Internal elements move but do not rotate.	Internal elements rotate.	Internal elements rotate.

The Nikon and Tokina are excellent. The Tokina is traditional while the Nikon is AF-S. Both are fast and accurate. it's easy to move the Tokina's ingenious manual focus ring forward or back to change between manual and auto focus.

The Nikon and Sigma are AFS, meaning you may just grab the focus ring at any time and take over manually from AF.

The Sigma is slower than the other two. It's "hypersonic" motor isn't. You can hear a high-pitched whine at about 10 kHz if you listen for it. Worse, the mechanics often make some unsavory squeaks as it focuses that don't engender confidence.

The Tokina and Nikon focus as you'd expect with any AF sensor.

The Sigma and sometimes the Tamron can have serious problem when using any sensor on my D200 other than the very center. Sometimes the Sigma won't lock focus with a side sensor. This means your D200 most likely (depending on your settings) won't shoot! In most modes the D200 needs to confirm focus before releasing the shutter. Often the Sigma won't focus perfectly enough with the side sensors, and will lock up the camera. This makes sense: the Sigma is generally the softest lens of the group. The D200 demands quality optics. If the Sigma can't get sharp enough in the sides to convince the D200 that it's in focus then the D200 won't turn on the green focus confirmation dot on the lower left of the finder and won't release the shutter! Look out for this, since when it first happened to me it confused me for quite a while.

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