When shooting in high-contrast light, all photographers are faced with the unnatural color-shift of chromatic aberration, and likely well-acquainted with the notorious green or purple fringe lining the edges of objects in our images.
Though a few tools to combat color aberration have been embedded in Adobe’s workflow for some time, cleaning up the lines in our shots has never been easier. Today we’ll take a look at an example and run through a few steps to correct these distracting hues by way of Adobe Camera Raw (ACR) and the Defringe tool.
What is Color-Fringe?
Adobe software developer Eric Chan provides a detailed insight into the challenges of chromatic aberration and the distinct color-fringing native to certain lenses from a software-design perspective at Lightroom Journal. I highly recommend those interested in further research to read the full article.
Here’s the story in a nutshell:
Red-green and blue-yellow fringes at the image periphery result from lateral chromatic aberration. This problem is relatively easy to fix…purple and green fringes in out-of-focus areas and along high-contrast boundaries are much more problematic.
These fringes result from axial chromatic aberration (wave-length dependent focus-shift), aberrations in sensor micro-lenses, and flare. In most cases, purple fringes appear in front of the plane of focus, and green fringes appear behind the plane of focus. The aberrations can happen anywhere in the image, not just the image periphery.
Axial chromatic aberration affects nearly all lenses, from inexpensive cell phone lenses to very expensive top-of-the-line lenses. It is particularly pronounced with fast lenses at wide apertures.
One simple way to diminish lateral aberration is by using a lens hood to block any light reflecting across the face of the lens. In harsh conditions, it helps to supplement the hood and shade by hand (or anything available) to ensure the best capture at the lens level. The closer the subject, the more control we have with shading and blocking. The more distant the subject, the more we find ourselves at the mercy of available light. Axial aberration is another beast entirely.
Removing Color Fringe in ACR
Please note: These steps can be similarly applied in Lightroom (if preferred) by navigating to the Lens Corrections tab in the Develop module.
For this example, I simply chose to point up and shoot directly into my light source to generate a high-contrast exposure. As is visible in the shot at left above, there is a prevailing purple halo, or fringe, located at the point of contrast where light meets dark. The image at right is what we’re after. Here’s how it works:
Step 1 – Open in ACR
Locate and select your image(s) in Bridge; click on the small aperture symbol (or CTRL-R) to edit in ACR.
Step 2 – Zoom to 100%
With the image open in ACR, zoom-in to acquire a closer view or select 100% from the fly-out in the lower-left corner.
Step 3 – Lens Corrections
With a closer view, navigate to Lens Corrections ? Color.
Step 4 – Defringe
First select the ‘Remove Chromatic Aberration’ box, then pan around the image to locate any purple or green fringes and drag the corresponding slider to resolve. In this case, simply drag the Purple Amount slider toward the right to remove the prominent reddish hue.
Images containing a high volume of aberration can be challenging, if not impossible to rectify in post. The more we drag the slider, the more the overall color of the image can be impacted. In some cases, we can crank the sliders, create a new layer and mask the changes in selectively (via Photoshop). In others, the best we can do is grab the camera and try again in a more reliable light.
For more tutorials in regard to this common problem, enter the keyword aberration into the search window above. I would recommend How to Beat Chromatic Aberration by Levi Sim and Reducing Chromatic Aberration in HDR Photos by Rich Harrington for further study. To access these tools in your workflow, be sure to check out the Adobe CC Photography plan and get the creative ball rolling full-steam for only 9.99/month.
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