New-to-me 12-40mm Pro and 40-150mm, testing sharpness performance

Started Nov 10, 2015 | Discussions thread
Astrotripper Senior Member • Posts: 4,896
How to test for lens defects

The easiest test to see if anything is wrong with the lens is as follows:

  1. Pick a target far enough for DOF to not be a problem (you want both center and corners to be inside DOF)
  2. Focus on the centre in S-AF mode and once focused, switch to MF
  3. Take the shot
  4. Rotate the camera 180 degrees along lens axis, you want to have exactly the same scene, but with camera upside down
  5. Take the shot
  6. Load up those two test shots to whatever graphics editor you have available. Rotate the upside down photo so that both have the same orientation.
  7. Switch between the two shots looking at corners
  8. If you see clear differences in sharpness in any of the corners, redo the test to make sure you did not messed up. If you get the same results, that means that lens elements are probably misaligned. Return the lens for a refund or exchange for another copy
  9. If you can't see any clear differences in any of the corners, congratulations, you got a "good copy" of the lens

Note: take the shots in good light, at ISO 200, without IBIS, and preferably with 0-sec anti-shock enabled. If you want to use JPEGs, make sure to disable Noise Filter and turn down Sharpness down to the minimal value, otherwise you'll just end up with sharpened mush. If the lens is busted, you should see that on JPEGs, sharpening can't usually make up for optical flaws.

If you really want to be super sure, shoot RAW and convert without any sharpening, using third party software that actually allows you to turn off sharpening.

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