Dynax 7D focusing test
updated 2004.11.25 - added comparison with Dynax 7
updated 2004.11.26 - added information about focusing from near limit and infinity
 
Testing procedure
I used the test procedure described here: http://www.photo.net/learn/focustest/.

  • All images is shot with the camera mounted on a tripod, using a cable release.
  • I tested all three AF modes, C, A and S, and could not see any difference, so I used S for the test.
  • In-camera sharpening at 0, no post processing except white balance adjustment.
  • Anti Shake is off.
  • I shot all images three times, focusing on my hand in between shots. There was no big difference between the shots, so the ones shown here is a random pick between the three.

  • Added 2004.11.26: I took some new test shots with the Minolta 24-105(D) and Minota 50mm 1.7 lenses, making sure focusing started both from the near limit and infinity, and sometimes from somewhere in between. Now matter where the camera started focusing, the focus ended up in the same spot. So it seems that the results does not depend on where the lens starts focusing from.

    All the tests were duplicated with my Dynax 7 loaded with Fuji Sensia 100, the film was scanned, and images from film is shown beside the images from the 7D.

    • Dynax 7D - ISO 100 Dynax 7 - Sensia 100 - Scan Dual II
    Minolta 24-105mm @ 70mm, f4.5
    Minolta 24-105mm @ 70mm, f4.5 Film Minolta 24-105mm @ 50mm, f4.5
    Minolta 24-105mm @ 105mm, f4.5
    Minolta 24-105mm @ 105mm, f4.5 Film Minolta 24-105mm @ 105mm, f4.5
    The 24-105 seem to back focus a little bit. Most noticeable at 70mm. The line is however acceptably sharp at both focal lengths. On film the 24-105 the situation is opposite, focus seems to be a little bit to the front. It also seems to be less obvious at the longer focal length.
    (I made a small error here, and shot at 50mm and not 70mm as with the digital image.)

    Minolta 100-300mm @ 200mm, f5.6
    Minolta 100-300mm @ 200mm, f5.6 Film Minolta 100-300mm @ 200mm, f5.6
    Minolta 100-300mm @ 300mm, f5.6
    Minolta 100-300mm @ 300mm, f5.6 Film Minolta 100-300mm @ 300mm, f5.6
    The old 100-300 (non-APO, non-D) is front focusing, but the line is again quite OK. The old 100-300 (non-APO, non-D) is front focusing on film also, but a little less obvious.

    Minolta 50mm, f1.7
    50mm-f1.7 Film 50mm-f1.7
    Slight back focus with the 50mm wide open. Slight front focus on film with the 50mm wide open.

    Cosina 100mm macro, f3.5
    Cosina 100mm, f3.5 Film Cosina 100mm, f3.5
    Cosina 100mm macro, f5.6
    Cosina 100mm, f5.6 Film Cosina 100mm, f5.6
    The cheap, plastic Cosina 100mm macro seem to be almost spot on. Maybe a fraction of back focusing. Same situation on film. Looking at the 100% images I am able to see the tiniest amount of back focusing.

    Conclusion
    Of my four lenses two backfocus a bit, one is front focusing, and one is spot on on the 7D.
    On my film 7 the two lenses which is backfocusing on the 7D is front focusing. The other two are about the same on film as on digital, the slightly better results on the film camera may very well be caused by the larger DOF on the film camera compared to the 7D due to the crop factor.

    All in all the results from both my cameras are pretty equal, and I don't think any of the lenses show unacceptable AF performance on any of the cameras. I think both my 7 and 7D is focusing well within spec, and I will now stop taking pictures of lines on paper and go outside and do som real photography :)

    All images Copyright (C) 2004 - Torstein Vee Haukvik - photo@haukvik.com