What Is a Tone Map and How Is Is Used When Editing Photographs?

When editing photographs applying a tone map means that you are changing the RGB value for pixels of a certain color or ‘tone’ within an image. Take for example a pixel with the RGB value 0,0,225 or blue; If you were to alter or ‘re-map’ the tone of the blue channel to produce a pixel with the values 0,0,180 and applied this map to all of the pixels with the value 0,0,225 within the image, you have tone mapped the image, drastically altering it’s appearance. Tone mapping is often used to approximate the appearance of HDR images by altering various tones within an image. The most popular way of applying a tone map to an image is by using your image editing software’s tone curve tool.