RAW Files

A Basic Outline and Guide to Understanding and Using 'Camera RAW'

Clive R. Haynes FRPS

Compensating for Lens Chromatic Aberration in RAW
Please note image sizes are fairly large to preserve detail, download times may therefore be slow.

An additional benefit of the Camera RAW dialogue-box is the 'Lens' tab.

In the dialogue box that opens one can adjust 'Chromatic Aberration'. This is a condition that often reveals itself where high contrast exists between edges in an image. It's the result of light 'splitting' as it's diffracted by the lens with the result that the light mis-registers when it strikes the sensor array (or the film plane in a conventional film-based camera).
The 'splitting' is caused by the different parts of the visible spectrum, being different frequencies and not 'bending' to the same amount (blue is diffracted less than red for example). 'APO' lenses are designed to overcome this phenomenon. However even 'APO' lenses can display a certain amount of fringing as the digital array reveals the chromatic error to a greater extent than film (the density of film base material tends to gently diffuse light and so mask the aberration).

The good news is that usually the effect is minimal and the better news is that in Camera RAW we can do something about it. Small improvements all add up to improved image fidelity - it's all quite synergistic!

The 'before & after' examples below show how adjustment in Camera RAW can reduce the effects of Chromatic Aberration.
Above: Almost 300% enlargement showing 'Colour Fringing' before Chromatic Aberration Adjustment
Above: Almost 300% enlargement showing reduced 'Colour Fringing' after Chromatic Aberration Adjustment
Next - 'Vignetting Correction' - Click the link below:


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