Eli5 How does a darkroom for developing photography work?


Eli5 How does a darkroom for developing photography work?

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It’s dark, because exposure to light will damage the image on undeveloped film or printing paper. Literally a small room with a light switch, and all sources of stray light from the outside sealed. Some will have a special red bulb that can be used without damaging blue-sensitive B&W printing paper.

Then the operator has to manipulate things in the dark, like unloading exposed film from the cassette and putting it in chemical developing tanks. Reloading bulk film into cartridges. Printing developed film onto paper with an enlarger.

Black and white film is developed into photographs in two stages:

1. Develop the negative;

2. Develop the final image.

To develop the negative, the photographer/darkroom tech pops open the cartridge, threads the exposed film into a special developing container, a light-proof canister with a spiral frame inside that suspends the film). This step must be done in complete darkness, by feel alone.

Once the film is safely inside the container, developing fluids are added and the container is agitated. After a certain amount of time the developing fluid is replaced with a fixing fluid (that stops the reaction and prevents over development) and then a rinse fluid (usually water). The result is a negative image of whatever the film recorded.

The negative image is placed in a projector which shines light through the negative onto light sensitive paper. The negative image is projected onto the paper for a specific amount of time. The paper is then processed through successive developing, fixing, and rinsing baths to yield the final image.

The light sensitive paper does not react to deep red light. So once the negatives are developed, the remainder of the darkroom work can be done under a dim red light.

The process for colour photos is a little more complex, so machines usually handle colour photos.