A700 af-speeds

[js1]

Hi folks,

Can anybody tell why there are two selectable af-speeds on the A700?
Is the faster less accurate and vice versa? Does the lower speed save the af-mechanism in the lens?
This is only my guessings, Can anybody tell for sure?

[01af]

I don't know either ... but a third guess might be noise. Slower = more silent (with conventionally driven AF, that is, not SSM). Just speculating.

-- Olaf

[Dr. Harout]

I use that mode whenever I'm using my Macro lens for a more accurate focusing (I think that was the point initially IMHO).
But please don't tell me "why should anyone use AF in Macro" cause I'm not talking 1:1 macro ratio.

[David Kilpatrick]

Accuracy is the official reason, but the technical answer is that some lenses may be damaged by the fast setting. These are, so far, known to be the 80-200mm APO f2.8 Minolta HS (high speed) and the Sigma 70-300mm f4-4.5 APO DG Macro (or earlier versions of this lens). There may be other HS revisions of Minolta lenses which could be damaged by the high speed setting. However, Sony issues no information and no warnings.

David

[Cecco]

Accuracy is the official reason,

Did you ever see a difference yourself?

These are, so far, known to be the 80-200mm APO f2.8 Minolta HS (high speed) and the Sigma 70-300mm f4-4.5 APO DG Macro (or earlier versions of this lens).

Can you give any reference for a 80-200 HS being damaged. I remember quite a few reports concerning the Sigma but never one concerning a Minolta lens.

Cecco

[David Kilpatrick]

80-200mm HS models were most often damaged by the 800si and Dynax 9, both of which have very powerful AF motors. I am not aware of any reports of damage from the A700, but I would set the camera to slow normal AF not fast if using one. I can not confirm more accurate focus with slow versus fast, as I have had both extremely accurate focus and slight errors in both modes with various lenses. I think there are more variables present in the average shooting situation than just slow/fast AF setting, which determine how precise the focusing is.

David

[Cecco]

80-200mm HS models were most often damaged by the 800si and Dynax 9, both of which have very powerful AF motors. I am not aware of any reports of damage from the A700,.
David

Good to hear you haven't heard of any reports of damage from the A700. It is not unlikely, the the newer generation A700 has a more intelligent control of the AF motor in compare to the Dynax cameras as well.

I can not confirm more accurate focus with slow versus fast, as I have had both extremely accurate focus and slight errors in both modes with various lenses.

That is exactly what I found as well. If there are slight errors, switching to slow AF doesn't help either.

Cecco