Why does infrared-based Dust and Scratch Removal not work with Black-and-White Film?

Black-and-white film (and also Kodachrome film) is a special case regarding dust and scratch removal. Its film emulsion contains silver halides, which, unlike color slides or color negatives, prevent the infrared light from the scanner to pass through the film emulsion. Infrared-based tools can not be used for black-and-white film and would even produce large artifacts in the image, which would make it completely useless.

SRDx – The Dust and Scratch Removal for Black-and-White Images

The SRDx Plug-in algorithms can easily detect dust and scratches, because their image information differs greatly from the surrounding image area. The algorithms pay attention to typical scratches (elongate and narrow) and are capable to remove them from the image. Unlike other tools for dust and scratch removal, SRDx does not apply a blur filter which would deteriorate the general image quality. The slider controls and options of SRDx enable the user to remove all image defects reliably without destroying any image details.

Photoshop SRDx Plug-in

The new standard for Dust and Scratch Removal