Why does this lens focus so fast on my K10D?

[fpser]

I put this old lens on my K10D: SMC Pentax-FA 28-80mm F3.5-5.6

I feel that it focusses a lot faster than my FA50F1.4, and certainly faster than the DA Kit lenses. More accurate too. I was playing around with it in fairly low light.

Anyone else have this lens and tried it on the K10D? Am I imagining things or do different lenses focus at different speeds on the same body?

Thanks!

 

[airconvent]

I used to have one before I sold it off. Did not feel any faster on the K100D though...

 

[hamustar]

maybe coz the lens component is not so dense and hence lighter=faster AF motor?

 

[kayster]

i think becos of its focus range is shorter... hence it dun need to hunt tat much..

 

[fpser]

i think becos of its focus range is shorter... hence it dun need to hunt tat much..

If by focus range you mean the angle the focussing ring must turn to get from one focussing distance to another, then a shorter focusing range should mean that there is more hunting since a small rotation might mean an overshoot.

Anyway, I'll play with the lens more. I have another 28-80 (the one with the power zoom). I'll try them both. Then when I get my DA lenses back from my sis (that's why I'm playing with the older lenses ), I'll compare them to make sure.

Thanks!