The Elusive Sockbird, or, testing the 40-150+TC

Discussion in 'Native Lenses' started by johnvanatta, Feb 25, 2015.

  1. johnvanatta

    johnvanatta Mu-43 Regular

    181
    Aug 5, 2014
    Oakland, CA
    I did some testing of everyone's hopeful new wildlife lens, the 40-150/2.8 TC'ed up to 210/4, today. Since they are easiest to view in sequence, I put them on my webpage.

    Starting with f4, then 1/3 stop increments. There's EXIF on the right to help keep track.

    http://johnvanatta.zenfolio.com/p711656735/h201B1A3F#h201b1a3f

    All are 100% pixel crops, center frame. Focus was, of course, on the eye, though it is easier to see how things work in the "feather detail". Taken with an EM-5 on a tripod in full sunlight, target 2-2.5m away.

    This is pretty impressive performance from a teleconverter. Kinda mucky at f/4, but it cleans up substantially by 4.5, and by f/5 things there's a load of acuity. Beyond f/5.6, there was no further improvement (and my tests got more inconsistent, shutter speed I surmise), just diffraction gradually taking its toll.

    My conclusion (from other tests as well) is that at f/4 things are underwhelming: it's probably worth taking it up to 4.5 and taking the ISO hit. At lower ISOs it's probably worthwhile to further push to get to f/5, maybe <800 or so.

    Considering that a teleconverter is mostly taking advantage of the difference between optical resolving power and sensor resolving power, this implies that the 40-150 should continue to be a high performer for a long time into the future.

    Okay, if you're still unwilling to click the link, here's the f/5 sample.

    2-03 - _OLY0877 q  _.
     
  2. johnvanatta

    johnvanatta Mu-43 Regular

    181
    Aug 5, 2014
    Oakland, CA
    Interesting, the forums automatically further recompressed the image, which had the side effect of getting rid of the digital artifacts present at the zenfolio version. Something to keep in mind.