12-40 f2.8 - Normal for some corners to be less sharp?

Discussion in 'Native Lenses' started by Tapper, Mar 13, 2015.

  1. Tapper

    Tapper Mu-43 Regular

    184
    Mar 12, 2013
    I recently acquired an EM5II with 12-40 f2.8 Pro.

    I noticed the bottom corners, especially the bottom right corner, is not as sharp as the other corners. Granted this is at 35 - 40mm @ f2.8. I've always heard people rave about this lens so just wondering if that may be within normal tolerances for this lens?

    Please see these examples below. Shot on tripod with IS off.

    Center - P3130961. R Bottom Corner - P3130962. R Top Corner - P3130962. L Bottom Corner - P3130962. L Top Corner - P3130962.
     
  2. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    The corners are normally a little bit soft at 40mm however are you sure you were parallel to the surface? The right top corner looks sharper to the center to me (if you take into account that the distortion correction is going to cause slight damage to the corners, you can see texture in the blue/green areas which you cannot see in the center).
     
  3. Tapper

    Tapper Mu-43 Regular

    184
    Mar 12, 2013
    Eteless, hmm, I'm not 100% sure. It's late and dark here now so tomorrow I will do more tests. Thanks for replying.
     
  4. budeny

    budeny Mu-43 All-Pro

    Mar 4, 2014
    Boulder, CO
    I remember similar thread for 12-40, maps were used for test too. Eventually lens was sent for warranty repair to Olympus and when returned it produced sharp results across whole frame.
     
  5. johnvanatta

    johnvanatta Mu-43 Regular

    181
    Aug 5, 2014
    Oakland, CA
    There's also a bit of forward field curvature at wider angles, I'm not sure about at 40mm. But if the bottom right is much worse than the bottom left it's probably skewed, or the subject isn't planar. It's really quite hard to get completely right-angle to a subject. Whether its "within tolerance" is anyone's guess.

    General consensus is the lens is a bit less sharp at 40mm than at 12mm.
     
  6. atnbirdie

    atnbirdie Mu-43 Regular

    53
    Apr 13, 2013
    Maryland
    If you do a lot of fairly close up copy work then this was a good test for you. If not, take shots of what you typically shoot and pixel peep them. That seems to me a more relevant test.
     
  7. cptobvious

    cptobvious Mu-43 Veteran

    239
    Jan 8, 2013
    It's not normal, but unfortunately most lens manufacturers don't do sufficient quality control for lens centering. I don't think it only affects close copy work; it also has affects deep DOF shooting like landscapes, particularly if the decentering is bad enough to still be noticeable stopped down.

    Assuming your test shots were done correctly (perpendicular to a flat surface) I would exchange for another copy.
     
  8. Tapper

    Tapper Mu-43 Regular

    184
    Mar 12, 2013
    Thank you everyone for your comments.

    So, I did more tests and have been able to get much better corners.

    I previously had the "Constant AF" feature turned on (tonight turned it off), and I think maybe it was negatively affecting final focus. Not absolutely sure, but that feature probably eats battery anyway. I was even able to get a pretty sharp corner-to-corner image *handheld* which amazes me (SEE BELOW). I have also found it's quite hard to get 2 flat planes perfectly aligned. But I think my lens is probably fine.

    The image below is an OOC JPEG.
    40mm, f2.8, ISO 200, 1/30 Second, Handheld with Auto IS

    P3150036.JPG
     
    Last edited: Mar 16, 2015
  9. Tapper

    Tapper Mu-43 Regular

    184
    Mar 12, 2013
    Here are the corners at 100%:

    Bottom Left
    Bot_Left_P3150036.
    Top Left
    Top_Right_P3150036.
    Bottom Right
    Bot_Right_P3150036.
    Top Right
    Top_Left_P3150036.

    Here is part of the center:

    Center_P3150036.
     
    Last edited: Mar 16, 2015
  10. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    I'm not sure how constant AF works however I suspect the problem was getting everything aligned - for testing I've used focus peaking so you can see the plane of focus (and the edges curving away) and getting all the corners roughly equal in falloff of peaking... however in real world I don't worry about it too much at all (I stop down when I can, if I can't it's because it's available darkness and any result is magic).

    TLDR: Yeap, that's sharp.