Godfrey DiGiorgi wrote:
On Oct 30, 2005, at 7:20 AM, Glen wrote:
The pix that G posted were of my first successful attempt with
trap focus. A very neat feature!
What is "trap focus"?
If you're using a manual focus lens on the *ist DS (and other models
of Pentax cameras, I'm sure) and leave the AF/MF switch set to AF,
the camera will block the shutter release unless the focus indication
registers positive, ie: that a focus sensor has locked in on a target.
(With manual focus lenses, only the center focus sensor is active.)
You can use this backwards: prefocus the camera with the shutter
halfway depressed to set a focus point that lights up the focus
indicator. Now aim the camera at the scene you want to capture,
perhaps a street with moving traffic in it, and depress the shutter
release all the way ... when something enters the focus sensor's zone
and comes into focus, the shutter will trip.
It's called "trap focus" because you've set the camera to fire, like
a trap, when the indicator light is triggered by the focus sensor.
Godfrey
The D will do this when in AF-S mode, at least with non-M42 screw
lenses. My D simply refuses to do reliable focus confirmation with a
screw-mount lens on it (I suspect this is due to the slight gap between
the lens and the contacts on the mount, it will sometimes do AF
confirmation and sometimes I get all AF points lit up on the LCD and no
AF Confirmation.
-Adam
