The black substance in the black and white photos is silver. Why?

Principle: Silver iodide is easily photodecomposed into silver and iodine, so the black substance in black and white photos is silver.

For most black and white films, the first chemical developer develops black silver grains in areas hit by light. The second liquid fixer used subsequently dissolves the unexposed silver halide, leaving a transparent film. Therefore, the result after rinsing away the chemical by-products and drying is a black and white negative.

Extended information:

The role of black and white photos in photography:

To be specific, photography is about subtraction. Photography is not about showing everything you see, but what you want to see. Converting color to black and white is also subtraction, but it is a subtraction in color rather than composition. Color can convey emotions, there is no need to go into details about this. Deleting color actually reduces part of the information in the photo, and the photo will naturally give people a different feeling.

When the photo has too many colors that interfere with the focus, making it black and white will reduce some interference. But it’s not just a matter of decolorizing black and white photos. It all depends on the retoucher as to what the contrast should be, which areas are bright and which areas are dark, whether the transition should be delicate and oily or as sharp as a knife, and whether a color cast should be done at the end. training.

Black and white can not only highlight the relationship between light and shadow, light and dark changes, and strengthen contrast for good works; it can also erase all color incongruities for bad works.

Baidu Encyclopedia-Black and White Photos