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
icon under the main preview panel) to inspect a part of the image, or zoom the main preview to 100% (also called 1:1)
.
General
- Comparison of sharpening tools
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:
- 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.
- Quantity: number of adjacent pixels to be analyzed when deciding what constitutes an edge. Higher values produce sharper edges and a greater "sawtooth" effect.
- Luminance only: the tool works in the L*a*b* color space and with this option, only the L component is enhanced.
Additional information can be found here:: https://web.archive.org/web/20110625093654/http://www.rawness.es/sharpening/?lang=en
Microcontrast
Microcontrast is a concept aimed at the distinction or separation of a pixel from its immediate neighbors, sometimes it is simply called contrast. However, an image with low microcontrast will have a number of neighboring pixels with similar values, meaning that there will be a number of areas without relief and hardly any detail. On the contrary, an image with a lot of microcontrast will allow you to distinguish the smallest details down to the pixel level and you will be able to differentiate a pixel from its neighbors.
For this reason, it is not recommended to consider the Microcontrast tool as another sharpening method, but as a way of improving the tonal graduations of an image i.e. it is about improving the distinction between different tones at the pixel level, so that the image has better textures and more depth in the lighter and darker areas.
Microcontrast is an often difficult to explain image characteristic that depends on several factors:
- the quality of the lens for the most part. There are lenses that are considered excellent but have poor microcontrast.
- the characteristics of the sensor and the demosaicing algorithm - (Amaze, AHD, VNG4, etc.) which have an important impact on the microcontrast (diagonals, colors, noise...).
- whether the sensor is equipped with an anti-aliasing filter or not (it will remove the finest details).
- whether the lens can differentiate details as fine as the sensor can capture them
- the presence of reflections inside the lens or even inside the camera when the image is shot. In these cases, blacks become dark gray and whites become light gray, which reduces contrast.
- whether the aperture has been stopped down to improve the depth of field: the higher the f-number selected, the lower the microcontrast of the photo.
- whether the aperture has been stopped down too much and introduced diffraction.