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Old Aug 7, 2011, 11:07 PM   #11
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That looks about right though. Certainly within standard tolerances. Better light will help.
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Old Aug 8, 2011, 7:30 AM   #12
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Originally Posted by Badguy75 View Post
Just got around to testing the focus with some charts, and I seem to have a slight back focus problem with the camers.
I didn't have much light to test with, so I will redo the tests tommorow when there is more natural sunlight.
I agree with peripatetic, that looks pretty good.

Try to get the chart square in the frame. Line the centre of the chart
up with the centre AF indicator point and the two extreme outer
AF indicator points. I know that is easier said than done at 400mm.

Testing indoors at 400mm and maximum aperture is a very stringent
test. DOF is virtually zero at f/5.6 and still only a couple of cm at f/22
unless you have a very big room and a very tall tripod. What is the distance
between the lens and the chart?

The T1i has two independent AF systems. Try comparing live-view
focusing with the main AF system. Use maximum magnification on
the LCD screen. Live-view focusing shows the actual image as seen
by the camera sensor, so it is inherently accurate. You should get
consistent results from the two systems.
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Old Aug 10, 2011, 10:19 AM   #13
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Thanks for the help everyone!

Been having nothing but cloudy days since the weekend, so no test chart tests!

The distance on the posted test chart pic was around 6 feet away, at an angle of about 45 degrees. Yes, the camera was tripod mounted and the tripod was fully extended, with me standing on a small step ladder to make sure of the focus!

Once we get a sunny day and better light, I'll snap up a few more, including some with live view focussing.
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