Focus issue with 9-18mm f/4.0-5.6 (Four Thirds) - faulty lens...?

Discussion in 'Adapted Lenses' started by jamespetts, Sep 21, 2016.

  1. jamespetts

    jamespetts Mu-43 Top Veteran

    803
    May 21, 2011
    London, England
    I have noticed a rather curious thing in one of my photographs taken with the E-M1 and the Four Thirds 9-18mm f/4.0-5.6:

    29550470520_312e174a6e_h. Hills and stream by James Petts, on Flickr

    The rocks in the foreground and the valley/trees in the background seem to be more in focus than the rocky outcrop/hilltop to the centre left. I am not quite sure how this can be: the focus, I think, was on the rocks, but this was taken at 9mm and f/5.6, so there should be a reasonably decent depth of field. Camera shake seems to me extraordinarily unlikely at 1/125 at 9mm with 5-axis stabilisation.

    Could this be a sign of a faulty lens? I bought it secondhand some years ago when I first got the E-M1. It has never been as good as some of the higher end lenses (I have to add quite a lot of sharpening in post usually), but it can give decent results sometimes.
     
  2. SVQuant

    SVQuant Mu-43 Top Veteran

    857
    Sep 20, 2015
    SF Bay Area, California, USA
    Sameer
    There were a couple of threads about generic 43-m43 adapters being a little off-plane and this effect being most visible in wide lenses. If you are using a generic adapter, that may well be the case here.
     
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  3. jamespetts

    jamespetts Mu-43 Top Veteran

    803
    May 21, 2011
    London, England
    Thank you for your reply. I am actually using a genuine Olympus MMF-3 (as I also use it with the weather sealed 50-200mm f/2.8-3.5 and MC-14), so it is probably not the adapter.
     
  4. barry13

    barry13 Super Moderator; Photon Wrangler

    Mar 7, 2014
    Southern California
    Barry
    Try a brick wall... make sure you're lined up and level.

    Could still be an issue with the adapter btw, wide angle lenses are much more susceptible to being off -plane.
     
  5. jamespetts

    jamespetts Mu-43 Top Veteran

    803
    May 21, 2011
    London, England
  6. PeHa

    PeHa Mu-43 Veteran

    206
    Nov 12, 2013
    Uppsala, Sweden
    I also have the FT 9-18 and two Oly adapters where I've noticed that one is better than the other. It's true as stated above that wide-angle lenses is much more off-plane sensitive than tele which explains why you haven't seen it with the 50-200. I've tried with AF-adjustments in the E-M1 to see if there's a point where it's acceptable alla over the image though it's not a real solution. If you have access to a FT camera you can check if the lens itself is ok (I have an E-620 on the shelf). Otherwise, of course, get another adapter...
     
  7. jamespetts

    jamespetts Mu-43 Top Veteran

    803
    May 21, 2011
    London, England
    Do you think that this is a faulty adapter?
     
  8. PeHa

    PeHa Mu-43 Veteran

    206
    Nov 12, 2013
    Uppsala, Sweden
    Well, the images look weaker on the left side, typical for off-plane caused by the adapter...
     
  9. jamespetts

    jamespetts Mu-43 Top Veteran

    803
    May 21, 2011
    London, England
    I see. I shall have to look into that. Thank you.
     
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  10. jamespetts

    jamespetts Mu-43 Top Veteran

    803
    May 21, 2011
    London, England
    After having read some articles on lens decentring, suggesting that ultra-wide angle lenses, zooms, and lenses with plastic bodies were particularly susceptible to this phenomenon (and noting that this lens is an ultra-wide angle zoom with a plastic body), and that this can cause exactly these symptoms, I took the lens into the London Camera Exchange on the Strand (where I bought the adapter) to see whether anything could be done (and also to try to test the lens with a Four Thirds body, if they had one in stock, to check whether the adapter was the problem).

    They did not have a Four Thirds body in stock, but the assistant noted that the front of the lens seemed to wobble slightly, and noted that even a tiny movement could cause problems with image quality (as indeed I had read in the articles). We managed to get the plastic ring around the outside of the front of the lens off (cracking it in the process; this was my over-enthusiastic removal of it rather than the assistant's; happily, this is only a cosmetic issue) and the assistant found a screwdriver that fitted the tiny little screws that were revealed by the removal of this ring. He found one screw that was a little loose, and tightened it. However, the front of the lens still seemed to wobble. I put the plastic ring back on, and looked at some other of the ultra-wide angle zoom lenses that he had in stock. I did not buy anything immediately, as I wanted to give the matter further consideration, but I did try out the PRO 7-14mm f/2.8 and the m.Zuiko 9-18mm f/4-5.6.

    On returning home and checking my pictures taken in the shop, I was surprised to find that the problem with my own lens did not seem apparent on the one photograph that I took with it (of a display cabinet with filters and boxes of film). It actually appeared sharper at the edges than the photograph of the same scene than I had taken with the 7-14mm PRO lens, but looking at that photograph carefully, it seems to be affected by motion blur at the edges (implied by a directional ghosting in high contrast areas rather than consistent blur, although it is somewhat odd to have had that at 1/60th of a second with the lens at 9mm and 5-axis stabilisation enabled, with the camera resting on the counter). Further photographs taken of my bookshelf just now seem more or less consistent: there is no significant blur on the left hand edge that I can find, although I am not equipped to test this with precision (albeit any problem that can only be spotted by testing with precision is not the most serious of problems in the first place).

    I wonder whether the screw tightening might have helped after all...?
     
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