Friday, December 7, 2012

Sony RX100 Distortion Correction

A not terribly well kept secret: most compact cameras (and many mirrorless cameras) do an enormous amount of image correction in camera after the image is taken.  This is true of cheap compacts and the more expensive as well.  Even cameras like the Canon S100 and Sony RX100 which support RAW are correcting for lens distortion, vignetting, and chromatic aberration in both JPEG and RAW files. 

As an example, here's an image that I took recently with a Sony RX100 processed using Adobe Camera Raw and Photoshop CS6:

DSC01766_DxOSony RX100, 1/640sec at f2.2, ISO125. © Andy Marfia 2012 All Rights Reserved.

And here's the image as the camera lens captured it:

Wonderland ForthcomingSony RX100, 1/640sec at f2.2, ISO125. © Andy Marfia 2012 All Rights Reserved.

Quite a difference, isn't it?  To get this second image, I opened the RAW file in DXO Optics Pro instead of Photoshop and then turned off all distortion correction.  DXO, as I understand it, removes Sony's correction and then applies its own, so by turning it off you can restore the photo to what the lens actually recorded.  Adobe Camera Raw doesn't give you this option.

I find this interesting for a couple of reasons.  For one, photographers used to believe that RAW files were, well, "raw", a more or less a direct capture of what the camera recorded.  This is definitely less true than it used to be.  Also, I suspect that most users of this camera will never know this correction is taking place, and probably never care.  The combination of lens design and software in this case is quite effective, producing extremely straight, sharp images, and 99% of the time that works just fine.  Sometimes though, I like an image that's a little less than perfect, and I'm glad that DXO gives me a way to revert back to that when needed.

Further Reading:
  • For more information on this trend towards in camera correction, I recommend this DPReview article from 2011: "A distorted view? In-camera distortion correction".  
  • I also found this blog post by Gary Friedman which talks specifically about the Sony RX100.  Here's his explanation:

    "Like other late-generation Sony cameras, the RX-100 employs Lens Correction algorithms in its .jpg engine designed to correct for distortion, vignetting, and chromatic aberration in lenses whose optical blemishes were well-understood. In the past it was used to correct mild flaws in existing lenses, but this is the first time I've ever seen an optical team give themselves permission to make a sloppy design, knowing that it can be fixed in software later. They went this route because there was no other way to make a perfect conventional zoom lens with that much reach that could collapse so much."

No comments: