Chromatic aberration Tab

Please note that this filter is not applied on the tabs where downsized  images are used for faster preview (Brightness, Color, Distortions, Frames tabs). 

To apply all filters and see the final result please switch to the Save tab. If you like the result, you can save it and process the next image. If you don't, you can always switch back to the filter, fine tune the settings and get updated result.

The program remembers the settings for each file you processed. So when you open a file again, the program recalls the most recent settings for this file. You can also save the file settings manually (Menu->Settings->File Settings).

Chromatic aberration (CA) is a complex phenomenon caused by optical effects and processes on camera sensor.

There are two major types of chromatic aberration that appear in digital cameras: first is purple fringing and the second is lateral CA. Helicon Filter fixes both types of CA.

To get better understanding, please read the following articles:
http://www.dpreview.com/learn/?/key=chromatic+aberration

Example of purple/blue fringing (blooming):

To fix this kind of CA the program does the following.
At the first step, it defines the areas with the brightness higher than the threshold.  These overexposed areas can cause blooming effect.
At the second step, the filter desaturates the pixels which are within radius from the bright areas.
 

 Use Lateral CA slider to distort red and blue planes of the image and compensate faults of the lens. Example of lateral CA:  

The Load Settings select box lets you choose one of the predefined settings for this tab. You can also save your current settings for future use.

The Enable CA reduction check box lets you turn the filter on or off.

The Radius slider defines the distance from the overexposed areas which will be desaturated. Try to find the minimum radius, which is sufficient to remove all CA artifacts.

The Brightness threshold  slider sets minimum level of brightness for definition of overexposed areas. The filter assumes that overexposed areas (>=threshold) cause a blooming effect, normal areas (<threshold) cannot cause CA. Try to find the highest suitable threshold value to minimize artifacts in other parts of the image.

The Color tolerance  slider defines precision of the color match for chromatic aberration. The zero level of color tolerance means that only an exact color will be removed (desaturated). Very high color tolerance (100) will include all color in the processing.

The Current CA color image and The Change button let you define the exact color of the CA artifacts by clicking with the mouse pointer on the image. Based on Color tolerance level, the program will look for similar colors and desaturate them.

The Reset button turns CA filter off and sets all sliders to their default values.

The CA Map button lets you switch to special mode, where intensity of blue color corresponds to the degree of desaturation. In this mode you can check where your image is affected.

Recommended workflow

• Reset to default values and turn CA filter on.
• Find the minimum level of radius which removes the most evident CA artifacts.
• Starting from a low threshold, find the maximum threshold, sufficient for removing all CA artifacts.
• Use CA map to check if other parts of the image were not affected.

To show or  hide Help panel of Helicon Filter use button from the toolbar or View->Help panel command in the main menu.