Tuesday 7 August 2018

post processing - Is pincushion or barrel distortion really all that bad in a lens?


Given that software can pretty trivially fix pincushion and barrel distortion patterns if you're shooting in RAW (Lightroom did the right thing just by knowing what lens I used with the given EXIF information), does it really matter if a lens has these types of distortion (so long as the are not so significant that the post processing does not lead to other significant artifacts of course)?


Reasoning for asking this:
I've found the distortion with the D7000's kit lens to be really bad -- but optically it's fine on pretty much every other front. Lightroom makes this go away, but I want to be aware of possible issues this might cause while I'm actually shooting...




Answer



No, it's not all that bad. On most shots, you won't be able to tell by eye if the curvilinear distortions have been corrected for or not - you'll need straight lines adjacently parallel to each other or to edge to tell. In nature, you won't have those lines. In portraiture, it will exaggerate some parts and diminish others, but perspective distortion and lighting has much more effect on result.


The reason you've heard so much about them is that you've read many lens reviews, and distortion is rather easy to measure and write about.


Possible downsides of shooting distorted and correcting in post:



  • you'll spend more time setting up and verifying your workflow;

  • in your heart, you might want to do as much as possible in camera (many cameras can correct JPEGs for manufacturer's brand lenses);

  • some contests have quite strict rules against manipulation in digital post-processing;

  • as Jerry Coffin already commented, slight loss of sharpness;

  • as you mentioned in your question, it's easy to correct if you're shooting RAW and your software knows the lens. These conditions might not be true for various reasons.



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