View Full Version : 50-200 SWD focus query

27th December 2011, 12:09 AM
I have the 50-200 swd from new about 10 months now. Great lens. Its done very little work.

Tonight i was messing about with it checking out focus speed etc. I mounted the lens on the E5 left the lens cap on and half pressed the shutter. The lens cycled from infinity to near and back to infinity extremly fast, this was with the lens at 50mm. i then zoomed into 200mm and repeated. The result was a much slower cycle, almost twice as long. when i zoom the lens back out to 150mm all seems fine again. Lens focus's perfectly at all focal lenghts with the lens cap off. it slows considerably between 150mm and 200mm. i then mounted it on my E500, same results but much slower between 150-200mm

Is this normal? any help would be great.

27th December 2011, 09:44 AM

Although I have not performed a test in the way you have, I have noticed AF performance degradation starting at ~150 mm. For instance, when capturing birds in flight with C-AF. Up to ~150 mm, finding and locking AF is usually reliable. Above 150 mm my experience is that risk increases either failing in locking or AF disengaging. For successful lock I usually turn AF to C-AF + Manual.

Same behavior is shown when using the lens on E-520 and E-600/620.

Could be that the behavior is "by design", to workaround the decreased lens speed at longer focal lengths (F2.8-F3.5)?


27th December 2011, 05:01 PM
Is it the aperture and light available to focus?

David M
27th December 2011, 05:12 PM
It's probably the protective filter.