Edges and Microcontrast

Edges and Microcontrast

The effects of this tool are only visible at a preview scale of 1:1 or more. Use a detail window (click on the

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icon under the main preview panel) to inspect a part of the image, or zoom the main preview to 100% (also called 1:1)

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General

• Comparison of sharpening tools
• 

  Unsharp Mask.

• 

  RL Deconvolution.

• 

  Edges.

• 

  Microcontrast.

• 

  Edges and Microcontrast.

• 

  Contrast by Detail Levels.

Unlike Unsharp Mask, Edges is a true sharpening algorithm. It does not introduce halos,it can be used on noisy images and it works in the Lab color space. Edges emphasizes edges only and can be used with Microcontrast to enhance the texture.

The designer of the 2 algorithms (Edges and Microcontrast) is Manuel LLorens (Perfectraw).

Edges

This tool sharpens any edges that have sufficient contrast for them to be considered as an edge. In other words, it sharpens edges that are already sharp, ignoring edges that have too little contrast. As mentioned above, the algorithm is not affected by image noise and does not generate halos.

This type of sharpening can make the edges look a bit unnatural, as if they had been “cut out”. Also, if the settings are too high, the resulting edges may show "aliasing" (staircase effect). This is why you should be careful when applying it to images with curved edges. However, when straight lines predominate (especially if they are not diagonal), it is a useful method of sharpening, especially if you reduce the size of the image at the end of processing.

To get the best results, the following settings are recommended:

1. Iterations (number of iterations carried out by the algorithm): A high number produces an overly sharp effect around the edges. With a value set to 2 this problem can already be observed in some cases. In general, 1 or 2 iterations give the best results.
2. Quantity: number of adjacent pixels to be analyzed when deciding what constitutes an edge. Higher values produce sharper edges and a greater "sawtooth" effect.
3. Luminance only: the tool works in the L*a*b* color space and with this option, only the L component is enhanced.

On the left, the original image. On the right, the image with the default "Edges" settings.The arrows indicate much sharper edges when the image is at full scale (at 100%), but if you open the image to view it at its actual size (equivalent to 200% or 300% in RawTherapee), you can clearly see the sawtooth effect and some slight posterization around the edges

Additional information can be found here:: https://web.archive.org/web/20110625093654/http://www.rawness.es/sharpening/?lang=en

Microcontrast

Quantity

Uniformity

A 3x3 matrix is better suitable for noisier images.