Keld Helmer-Petersen was a Danish photographer who used the technique of thresholding in his photography.

At the start of his career, his aim was to make pictures that would only work in colour, and not in black and white. When he began focusing on architectural photography, he then used the black and white effect .

The simplest thresholding methods replace each pixel in an image with a black pixel if the image intensity is less than some fixed constant or a white pixel if the image intensity is greater than that constant.