70-200 4 L Focus Tests

[yb98]

I have made some test shots to see if my 70-200 4L has back focusing problem or not, and it seems ok at all focal lengths except the 70mm length...
Is it possible to have back focus at a particualr focal length only ??? or is it because the focus region is bigger in the case of 70mm ?

Here are the 100% crop test shots. All shots were taken at ISO 400, f4.0 focus on the center line.

70mm
http://bellik.free.fr/70.jpg

100mm
http://bellik.free.fr/100.jpg

135mm
http://bellik.free.fr/135.jpg

200mm
http://bellik.free.fr/200.jpg

Yacine.

[KennyG]

Your test is flawed. You can not test on a target that is at an angle. You should use a target that is flat face on to the camera and angle the ruler so that you can see if it has front or rear focus.

This has been mentioned many times, please do a search.

[Jehel]

Yes, it is possible to get back focus or front focus at a specific value.
However, the test tou ran is not the best.

[Kabz]

:roll: come on....
you should know better :lol: