« on: February 22, 2014, 11:36:14 PM »
It was so cold my wife had to thaw out the feeder every couple of hours.
Model: Canon EOS 7D
Exposure: 1/200 sec
Focal Length: 105mm
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I've had mine for several years and have never been disappointed with it. I shot the America Cup races with it on a monopod using the 1.4 and 2.0 TC together for 1120 mm total. Shooting the Cats at 50 MPH it did great. You can see the images at FM Forums under sports.
Maybe in the future, but I really need a macro right now.
Here is an example of a "real world" test case where it's pretty easy to tell, without pixel peeping, whether or not you have a issue with front or back focusing.
Canon EOS 7D
Focal Length 400mm
F Number f/5.6
Is it? Its just one image. Things are not quite so simple.
Please consider the following:
The Canon AF system varies from shot to shot, so a thorough test requires that you take several shots setting the lens to infinity or mfd before each shot. Then you need to throw out obvious misfires, and average the others.
That one image that appears to be perfect could, in fact be a misfire, and the other nine be OOF.
2. With a wide aperture lens, the depth of field is very shallow, so its difficult to spot the exact focus on a three dimensional object.
3. You do not "KNOW" exactly where the camera tried to focus, it could have been on the beak, the foot, the tail, or the board the bird is standing on. A properly designed target will insure that the AF system will try to focus on the same spot every time.