On Jan 11, 2010, at 00:13 , Larry Colen wrote:
On Jan 10, 2010, at 2:23 PM, Rob Studdert wrote:
On 11/01/2010, Joseph McAllister <[email protected]> wrote:
I know. I photograph running and playing dogs almost every day. A
large dog
running towards me from 100 ft away, sunny day, K20D center
focused, high
speed continuous, ƒ4 60-250 @ 135mm, may occasionally result in
one sharp
image. If you don't even shoot, just watch the image through the
finder, you
can see that the camera focuses, stops, focuses, stops, etc.,
sometimes
catching up, and never predicting the location of the subject soon
enough to
actually allow the shutter to trip when it arrives.
It's a travesty.
You might appreciate this little 7D test video:
http://canonfieldreviews.com/7d-cold-winter/
I haven't even fantasized about autofocus that works that well. I
can see that if I were to start photographing fast moving objects
then there is definitely something a lot better than Pentax.
Correct me if I'm wrong, but isn't this a matter of fast computation,
well written code, and tight tolerance of the mechanicals that will
put an image in focus on the sensor, assuming that the sensor stays in
the same plane at all times?
The system speed and the code should be a given, even if Pentax had to
license it from whoever has written the code for N & C.
The lens mechanicals can be iffy, as proven by the poor QC that has
surfaced from time to time coming off the Pentax assembly line.. There
may be inherent slop in the camera body driven focus, but SDM should
be flawless, unless Pentax is trying to get away with an insufficient
number of steps in the stepper motor of SDM.
Having a sensor that wiggles around in an attempt to follow a moving
image at the plane of focus could be part of (my) the problem. Most
all of my images are hand held, and I know for a fact that taking a
breath, letting it half out, and relaxing to take the shot only
removes about 50% of my shake. Damn! It irritates me to see the finder
focus lines dancing around within the image displayed!
However, when I put the camera on my sturdiest tripod, step back and
let it settle after either auto-focus OR critical focusing with a
magnifier, us a two second delay, drape weights over the rig, and
still get soft images at infinity, close, or anywhere in between,
something's wrong.
Not that they never happen. They do. It's just that I can't know if
they are sharp until I get home and d/l to my computer if it was worth
getting out of the house that day that disappoints.
My last hurrah is going to be replacing my K20s with a K7, and getting
a gimbal mount to use when shooting action shots of dogs, birds, and
kids. If that doesn't do it, I'm going to get a job cooking at a
Benihanas to prove my motor skills, one finger at a time!
Joseph McAllister
[email protected]
“ It is still true, as was first said many years ago, that people are
the only sophisticated computing devices that can be made at low cost
by unskilled workers!”
— Martin G. Wolf, PhD
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