Digital Focus

Advanced Editing in LR (Last Part)–

Chromatic Aberration

 

Chromatic Aberration  is a common defect caused by the failure of the lens to focus different colors to the same spot. In one type of chromatic aberration, the image from each color of light is in focus, but each image is a slightly different size. This type of aberration is seen as a complementary color fringing in areas away from the center of the image. See Image 26.

To see the chromatic aberration, zoom in to an area that contains very dark or black detail (hair of a person) against a very light of white background (sky).  In the Chromatic Aberration pane of the Detail panel (Image 27), adjust any of the following depending on the color of the fringes:

Red/Cyan adjusts the size of the red channel relative to the green channel. The slider compensates for red/cyan color fringing. Blue/Yellow adjusts the size of the blue channel relative to the green channel. It compensates for blue/yellow color fringing.

To  see better the color fringing you are trying to remove, press Option (Mac OS) or Alt (Windows) as you move a slider to hide any color fringe corrected by the other color slider.

Instead of using the color sliders, you can also use the Defringe (Image 28). When you click the double arrow opposite it, you have access to Off, which turns off defringing; All Edges, which corrects color fringing for all edges, including any sharp change in color values; and Highlight Edges, which corrects color fringing only in the edges of highlighting where fringing is most likely to occur. Choose Highlight Edges if choosing All Edges results in thin gray lines or other undesired effects

 

Vignettes Panel               

This panel addresses the issue of vignetting. Vignetting is a lens defect that causes the edges of an image, especially the corners, to be darker than the center. It is particularly noticeable when the photo contains a subject that is supposed to be an even shade or tone, such as the sky in a landscape photo. Vignetting can also be caused by using a wrong hood or overstocking of filters.

The sliders under the Lens Corrections pane (Image 29) are meant to correct these apparent lens distortion. Lens corrections can be applied only to original, uncropped photo edges. Move the Amount slider to the right (positive values) to lighten the corners of the photo. Moving it to the left (negative values) gives  opposite result. Use the Midpoint slider to control the Amount adjustment. When removing the vignette, drag it to the left (lower value) to apply the adjustment to a larger area from the corner. Dragging it to the right (higher value) restricts the adjustment to an area closer to the corners.

Ironically, in the first version of LR, most photographers use this panel not to remove the vignette, but to add a vignette to a photo as an artistic effect (Image 30). At that time, however, adding a vignette was only possible for an original photo. If the photo was cropped, adding a vignette was no longer possible and whatever vignette was applied to the original photo disappeared. So in LR 2, the developers of LR added the Post-Crop vignetting option (Image 31), which allows a vignette to be applied to a cropped or uncropped photo.

The options under the Post-Crop vignette are: Amount and Midpoint which  works exactly like the Lens Correction sliders; Roundness which defines the shape of the circle—lower value for oval and higher values for more circular effect; and Feather which softens the edges of the vignette—lower values reduces the softening, higher values increases the softening.

 

 

Camera Calibration Panel           

LR uses two camera profiles for every camera model it supports to process raw images. (Profiles are like the “bio-data” of a device that defines its behavior (how it produces or captures colors). The profiles are produced by photographing a color target under different white-balanced lighting conditions. When you set a white balance, LR uses the profiles for your camera to extrapolate color information. These camera profiles are the same ones developed for Adobe Camera Raw. They are not ICC color profiles and may or may not reflect the real profile of your specific camera.

To make the profile more camera specific, you can use the Camera Calibration panel (Image 32) to adjust how LR interprets the color from your camera.

The panel is broken down into Profile, Shadows, Red Primary, Green Primary and Blue Primary.

 

Profile

In the panel, you can choose a profile that you think best suits your photos (Image 33). The options are:

ACR (version).  These profiles are compatible with older versions of Camera Raw and Lightroom. The version corresponds to the version of Camera Raw in which the profile first appeared. Choose an ACR profile if you want consistent behavior with legacy photos (photos taken before LR2).

Adobe Standard.  These profiles significantly improve color rendering, especially in warm tones such as reds, yellows, and oranges, from earlier Adobe camera profiles. The Profile pop-up menu displays only one Adobe Standard profile for your camera.

Camera Matching. These profiles attempt to match the camera manufacturer’s color appearance under specific settings (for example, Canon’s Picture Style). Use a Camera Matching profile if you prefer the color rendering offered by your camera manufacturer’s software. Camera Matching profiles include the prefix Camera in the profile name.

Embedded.  Indicates that the current file (a FIFF, JPEG, or PSD photo) has an embedded profile.

Note:  Adobe Standard and Camera Matching profiles are based on the DNG 1.2 specification.  If they do not appear in the Profile pop-up menu, download the latest LR update.

 

Shadows

Use this to correct for any green or magenta cast in the shadow areas of the photo.

 

Red, Green, and Blue Primaries

You can use this sliders to calibrate your camera and save the calibration as a Develop preset. Shoot a standard color target under the lighting you want and then try to match the result with the standard by moving the sliders. The process, however, is not plug and play. It is really more like plug and pray. So I will not even attempt to discuss the process here.

This completes the advanced editing features of the Develop Module. In the next issue, I will discuss the various tools found in the Tool Strip.

 

(Jun Miranda is the first Philippine-based Adobe Certified Instructor,  Adobe Certified Expert for Photoshop CS, and CompTIA’s Certified Technical Trainer. He is also the President and Program Director of the Philippine Center for Creative Imaging, Past President of the Camera Club of the Philippines, the founding president of the Club de Camera Digital and a member of the National Association of Photoshop Professionals.)