eli5: Tintype photography


How does it work?

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This is kinda too specific/technical for an ELI5 but basically: a box camera is set up in front of a subject. In a low-light setting a photographer coats a tin plate with light sensitive chemistry. When the plate is ready its placed in a special holder with a sliding cover that prevents it from being exposed to light. The subject is readied, the camera focus is set, and then the holder is inserted in the camera. The film holder slide is pulled, and then the lens is opened while the photographer times the exposure. When the exposure is done, the lens is closed, the slide is set back in the holder, and the holder is brought back into the darkroom where it is chemically processed. After processing the resulting tintype is the only copy. Unlike glass or film negatives, tintypes area a “direct positive” process like a Polaroid, making an image suitable for viewing without a reproducible negative that requires printing.

Normally, when taking a film picture, silver crystallizes at the areas exposed to light, and these crystals form the dark parts of a negative. Then a picture of the negative is taken, flipping the dark and light parts around and giving you a recognizable image.

On a tintype, the initial reaction happens on a blackened metal sheet, so the areas without silver crystals look black. Extra chemical processing brightens the silver crystals, thus directly forming a black-and-grey image without any need for a negative.

Tintypes are kind of like old-timey Polaroids, in the sense that they are one-off (you don’t create a negative that you then print) and “instant.” This is called a “direct positive” — one of a kind, and created directly in the camera.

**The funny thing about tintypes is that they are actually, technically, negatives.** The metal plate that a tintype is made on is dark in color, which makes the light-sensitive substance that forms the image appear to be a “positive” image instead of a negative.

If you are interested in the actual mechanics of how cameras work….

The beginning of the tintype process is similar to other forms of analog photography, in many ways:

– Find a material that is reactive to light (like film in a typical analog camera). In the case of tintypes, metal plates are coated with special chemicals known as a “collodion emulsion.”

– Put your light-reactive material into a camera.

– Open up the camera lens to allow light in for a certain amount of time. This is the “exposure.” The camera lens allows light to hit the light-reactive material. The lightest spots in the scene make the light-reactive material very dark, and the darkest spots in the scene stay light.

So now, you have a piece of metal with a “negative” image on it (dark parts are light, and vice versa).

Here’s where tintypes are different than most analog photography. With a typical film camera, at this point you’d use the _negative_ that you created to produce one or more _prints._

With a tintype, you don’t use a negative to create a print. The image is created directly on the metal plate:

– Put the metal plate into another chemical, a “fixer.”