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Re: [Canon-10D] Re: Lens no Focus Bruce Ward Thu Apr 05 15:01:24 2012

You didn't do the test correctly.  The camera needs to be on a tripod 
with the lens axis parallel with the floor about 6' from the target.  If 
you Google for this test you'll find some good information on it and 
often including the target you can print and use.  There needs to be a 
small object of high contrast for the camera to focus on and this object 
is placed just to the side of the yardstick or other target and is 
placed exactly perpendicular to the lens axis.   This will aid in 
accurate focus acquisition.  You can also find information that this 
test is not always accurate, no matter how it is run, with cameras with 
only 9 focus points.  It has to do with the accuracy precision (or lack 
of) of the focus points.

Bruce


On 4/4/2012 8:37 PM, gary.chris wrote:
> I tried a version of your test and they were not conclusive because the
> angle of me standing and looking down, at an angle, at a yardstick and a
> book ( for the AF) vertical at the 20" point. I should have angled the
> book backwards a slight bit so to have a flat surface facing the lens.
>
> I took a photo using the auto focus first and 19" was in focus, not 20".
> I took another photo using manual focus and it was right on at 20".
> The lens I used was the 100-400 at 400mm f.5.6.
>
> The problem is that I am not quite sure where the point AF actually
> focus on. If it focused high up on the book, that would put it closer to
> me and 19" might be correct.
>
> I have to do it again and pay attention to the details.
>
> I'll get back to you guys.
>
> Thanks a lot - really helpful.
>
> Gary
>
>



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