70-200 Sigma 2.8 EX HSM

[brianhare]

Does anyone have this lense,,,i was wondering if there is a switch on this to turn off the autofocus,when you want to manual focus.i have a D50 and when you leave the camera switched too autofocus and focus on something,,,you can still rotate and manual focus this lense????...seems to me i`m doing something wrong,,,,or the lense will let you adjust the focus even after the camera has focused???...which means you could actually throw this out of focus if you put your hand out too far and moved the focus ring by mistake after the camera already focused???...does anyone understand what i`m saying,lol....clarification on this would be appreciated as the kit lense requires you to switch to manual focus....

Brian

[brianhare]

I guess it`s normal from what i`ve found out on another forum,thought it likely was as there was no switch....



Brian

[NHL]

brianhare wrote:

,,,you can still rotate and manual focus this lense????...seems to me i`m doing something wrong,,,,or the lense will let you adjust the focus even after the camera has focused???...

This is actually a very nice feature resulting from the HSM (ultrasonic) mechanism...

-> It's called full-time manual overide of the AF, and is only available on the silent focus ultrasonic lenses with no need to flip the AF/manual switch first. The switch is there only to permanently disable the AF! :-)