A friend of mine had a similar issue with his Canon 10D. His
manually focused exposures were never quite on the money, but AF
exposures were bang on target. After a suitable and similar
round of measurebating, he concluded that the focusing screen
was in need of shimming ... It was representing a focus plane
some small fraction of a millimeter off from where the sensor
was. Autofocus worked fine because it evaluates focusing
distance through a completely different set of optics and
parameters than manual focus.
He had his camera adjusted by Canon and now it focuses
precisely, both in MF and AF. I believe they shimmed the
focusing screen.
Godfrey
--- "Gonz" wrote:
> I need some help with my *istD. For the longest time, I've
been
> having problems with my pics being quite soft wide open. I
> thought that it was just because the lens was wide open. I
have
> alot of manual focus lenses, which I use often. The problem
> showed up mainly with them, so I went back to look at some of
the
> pics more carefully, and I noticed a pretty consistent
pattern.
> There were areas of sharpness alright, but not where I wanted
> them to be. I was consistently back-focusing. So I did some
> tests. I mounted my FA* 85 1.4 on the camera, set it on a
> tripod, and proceded to make some careful experiments to see
if I
> could put the blame where it belonged, on me or the camera.
>
> The setup was your typical measurebating focus test setup. I
had
> a ruler at an angle with a target off to the side of it where
I
> focused. I took pictures with and without autofocus. The
result:
> no matter how carefully I manually focused, the autofocus was
> always right on the money, and I always back focused. I
adjusted
> the diopter after autofocusing to see if I could match the
> camera's focus point, took my glasses off, put my glasses on,
> danced around the camera, but no matter, I always
back-focused.
> What is going on here? Doesnt the autofocus see the same
thing I
> do? Or is something mal-adjusted somewhere? When I look
through
> the viewfinder after I auto focus, it seems to be in decent
> focus, but it looks pretty much the same as when I focus
> manually. If I then switch to manual focus and get it out of
> focus and back in and take the pic, it is back-focused! Am I
> going blind? ...
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