Introduction to CornerFix

What is CornerFix?

CornerFix corrects for vignetting effects in digital images. It's most often used to correct for the color vignetting that occurs when wide angle lenses are used with digital sensors that include IR filters, resulting in so-called "Cyan Corners". The two screen shots below show before and after images of a CV12 lens mounted on a Leica M8 with a 486 IR filter. However, CornerFix can also be used to correct for simple optical vignetting, e.g., for stitching together panoramas, as well as to correct more complex effects e.g., "Italian flag" syndrome (green on the left, red on the right) such as found on the Leica M9.

CornerFix For Windows

CornerFix for the Mac

CornerFix was originally written for the Leica M8, but now supports any camera that either:

    • directly produces a DNG format image file, or
    • produces an image that can be converted to DNG.

This covers, for example, the Leica M8, M9, X1 and S2, and converted images from the Sony NEX series, the Sigma DP series, all known DSLRs from Nikon, Canon, Sony, etc, etc. Chances are, CornerFix will work with your camera.

IMPORTANT: CornerFix, Aperture and Mountain Lion........

Got a problem with green images using Aperture on Mountain Lion? See this page.


    • Corrects for multiple vignetting related issues - "cyan corners, "red corners", "Italian flag syndrome", etc, etc
    • Either Mac or Windows versions
    • Works with almost all cameras - any image that can be converted to DNG form
    • Allows the use of lens not supported in the camera's firmware, or not coded
    • Allows corrections to be adjusted separately for luminance and chroma
    • Corrects at the raw data level, so any raw developer can still be used, e.g., C1, Lightroom, etc
    • Profiles for any aperture and/or and lighting can be produced
    • Free – distributed under the GPL. Note that some portions are copyright Adobe.
    • When used with Leica M8 or M9 cameras, decodes the Leica MakerNotes, and can optionally update the DNG file's EXIF data with an estimated aperture value

How does CornerFix work?

CornerFix works by first analyzing a reference image (of a gray card, white wall or whatever) in order to build a lens profile. You then use that lens profile to correct images taken with that combination of lens and camera. So using CornerFix is a two step process:

    1. Take a reference image for your combination of lens and camera, and use that to have CornerFix build a lens profile, then
    2. Use the lens profile to correct whatever images you've taken with that lens and camera.

Note that CornerFix doesn't come with a library of profiles - you have to build your own.

System requirements

CornerFix requires the following:

    • Under Windows: Windows XP or later
    • On the Mac, for Version or later: OS X 10.6 (Snow Leopard) or later, Intel only
    • On the Mac, for Version or earlier: OS X 10.4 (Tiger) or later, Intel or PowerPC


Project hosting

CornerFix is hosted on Sourceforge:

Get CornerFix at Fast, secure and Free Open Source software downloads