Toning prints with selenium causes a chemical change to silver molecules that improves the stability of the image
under display conditions. Depending on the materials and the way the toner is used, the color tone of the image may change.

While digital imaging has largely replaced silver-based photography, many still long for the craft of black-and-white darkroom work. Prints made on silver halide papers have good resistance to fading over time when kept out of direct sunlight and bright lighting.

Tech talk
Prints toned generally have higher density and contrast than untoned prints. They also have a higher maximum density.

Aesthetically
The look and feel

Digital toning

Toning can be simulated digitally, either in-camera or in post-processing. The in-camera effect, as well as beginner tutorials given for software like Photoshop or GIMP, use a simple tint. More sophisticated software tends to implement sepia tones using the duotone feature. Simpler photo-editing software usually has an option to sepia-tone an image in one step.