How does one correct magenta cast in Lightroom 1.1?

[etrigan63]

I have some test images with the Leica M8 magenta cast on black issue. Folks here have mentioned that it is easy to correct. Would any care to explain how? Images are DNG adn I develop using Lightroom 1.1.

 

[willie_901]

Lightroom does have Split Toning controls that let you independently adjust the color cast of the highlights and the shadows. Certain images will benefit from this type of processing.

There can not be a universal post-processing fix for IR contamination. It is impossible to know how many of a particular pixel's photon counts are from IR energy. If IR photon contamination could be properly removed with a post-processing software solution, this software would be readily available and used with all digital cameras.

Often the magenta cast is obvious because an object that is know not to be magenta becomes magenta. However altering the IR contaminated pixels will also alter the color cast of pixels with no IR contamination. Faces and other skin areas with blood flow near the surface will also exhibit IR contamination. If you think only synthetic black fabrics have IR color distortion, then look at a gallery of photographs taken with IR film.

 

[Gid]

Shoot B&W 😉

 

[Gid]

Here is something you can try. I used this before I had any IR cut filters and it gives a reasonable result.

Set the white balance using the eye dropper tool if required.

Set vibrance to -20

Go to HSL, click on colour and then magenta (last button on the right)

Set hue=0, saturation=-74 and luminance = -58

Go to camera calibration

set shadows tint to -79

End

The above worked for me in the majority of situations (was good enough), but it is not an exact science and you can use this as a starting point. In some instances just setting the shadows tint to -79 does the job.

Good luck.

PS. Once you have a set up that works then save it as a preset.

 

[jlw]

I have some test images with the Leica M8 magenta cast on black issue. Folks here have mentioned that it is easy to correct. Would any care to explain how? Images are DNG adn I develop using Lightroom 1.1.

[edited once I had Lightroom in front of me]

Here's the hot tip: Use the Camera Calibration section. In the Develop module, scroll down to Camera Calibration. Right at the top of the section, you'll see a slider named Shadows[/i], which you can move toward either green or magenta.

Just move this slider slightly in the green direction until your black areas look neutral. Once you've got a setting that works, save it as a preset so you can apply it easily to other photos of the same subject taken under the same conditions.

I've done this to treat IR contamination of blacks in pictures from my R-D 1 (which doesn't experience this issue as much as the M8 does, but still encounters it occasionally.) It's quick, easy, and usually does all you need to fix it.