On 10/22/07, karl shah-jenner
<shahjen@xxxxxxxxxxxx> wrote:
October 18, 2007 2:02 PM PDT
Canon has fix for high-end SLR autofocus
Posted by Stephen Shankland
An adjustment to one mirror should fix an autofocus problem that has
tarnished the debut of Canon's high-end EOS-1D Mark III camera, the company
said Thursday.
"We're pretty confident this countermeasure will resolve the issue
completely," said Chuck Westfall, a Canon spokesman and tech guru. "It
feels nice to have a little bit of light at the end of the tunnel and know
it's not another oncoming train."
The US$4,500 camera, geared chiefly for photojournalists who can appreciate
features such as its 10.5-frame-per-second shooting ability, had won
accolades for most of its design. But photographer and consultant Rob
Galbraith dug up problems that cropped up in bright or warm conditions. The
problems were also confirmed by others including Seattle Times photographer
Rod Mar.
Canon was able to reproduce the problems. "What we found out after our
thorough research is this issue seemed to manifest itself more in cases
where the temperature was high," Westfall said.
Not all cameras are affected, but Canon doesn't know which are or aren't,
so anyone having the problem should send the camera in to be repaired,
Westfall said. Once it's ready to begin repairs, Canon will publish
instructions on how what photographers should do, probably in the next two
or three weeks.
New cameras coming off the line don't have the problem, he said.
The problem involves a mirror that directs light to the camera's autofocus
subsystem. "That mirror needs to be adjusted," Westfall said.
Single-lens reflex (SLR) cameras have a main mirror that directs light from
the lens to the viewfinder, so photographers can see what they're shooting.
But some light passes through that mirror, traveling instead to sub-mirrors
that direct light to the autofocus system's sensor. When a photographer
takes a picture, both the main mirror and the sub-mirror for the autofocus
system flip out of the way to let light shine on the camera's main image
sensor.
The problem with the sub-mirror could mean the camera would focus in front
of the subject or behind it, Westfall said. "If that sensor is not
receiving reliable information, it's not able to carry out correct focus
prediction," he said.
(Via Rob Galbraith.)
k
--
Alex Georgiadis
