If chromatic aberration is a problem for you, there is a simple method of fixing this lens-based problem in the digital darkroom. Here is our simple guide to fixing color fringing when shooting against white backgrounds.
Isolating a subject against a white background is a familiar stock photography technique utilising simple studio lighting with dedicated lights blowing out the background while a foreground key is balanced for the subject.
However, if your background lights are a few stops higher than the key then you’re increasing the chances of colour fringing occurring on high contrast edge areas.
You may have come across chromatic aberration, as the effect is technically referred to, in snapshots of darkened trees or building edges against a bright sky, or reflected highlights on lapping water.
These items adopt a hazy line of red or blue at the edges of contrast where light wavelengths converge. The distortion is a lens-based issue that even the most expensive lenses can generate in such high contrast situations.
In the studio, you can reduce the chances of this occurring by balancing your key and background lights and reducing the extremes in strength.
If this isn’t possible, there are methods for reducing and even removing this through post-processing in Photoshop.
The most immediate choice is to make use of the dedicated tools in Camera Raw found under the Color tab of the Lens Corrections options.
A simple one-click method is available but be sure to zoom in to at least 100% on a problem area that includes both the blue and red fringing found most commonly along the left and right verticals respectively to determine how effective the automated method is. Manual sliders are available if you feel a little more adjustment is necessary.
An alternative method for more localised problems such as specular highlights in eyes or teeth reflections is to selectively desaturate the problem area.
This can be done by painting black or white onto a newly-created blank Hue/Saturation Adjustment Layer with a soft-edged brush small enough to be effective – just remember to zoom into your image adequately to restrict the removal of colour to the problem areas.
Of course, you could achieve the same results by changing the Blend Mode of the Brush tool to Hue and painting directly onto the image.
With an Adjustment Layer, you have the non-destructive freedom to backtrack if you feel the effect isn’t quite as satisfactory as you’d hoped.
Step-by-step how to fix chromatic aberration on white backgrounds
01 Identify the problem
At 100% magnification, we can see the blue and red fringing running down the vertical edges of the suit trousers of a model wearing a dark suit against a brightly lit white background.
02 A quick fix
From within Adobe Camera Raw, choose the Color tab under Lens Corrections and then check the Remove Chromatic Aberration option. View at 100% and make use of the manual Defringe sliders if necessary.
03 Manual correction
For overlooked areas, create a blank Hue/Saturation Adjustment Layer and paint over any additional problem spots with a black or white brush to desaturate the fringing or specular highlights such as catchlights.
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