Fine art macro photography (Image formed on the film/paper is larger than life size). These images have been made in antique cameras, vintage cameras and DIY cameras, using a variety of processes, but mostly paper negatives.
I use photographic paper instead of the glass plates that would have been used originally. The paper is not sensitive to red light (orthochromatic) so produces an image with a "different' feel. The image produced on the paper is a negative image - back to front, upside down, light areas darken the paper, the darker areas appear light where the white paper has not reacted to light.
See if you can pick out which of the images here are the original negatives - and which have been made into positives - either with Photoshop, or by contact printing onto a second piece of photographic paper. In contact printing a light is shone through the negative image onto photographic paper below so that light areas of the negative let light through and darken the paper below, shadowy areas on the negative prevent light getting to paper below producing the lighter tones and a positive rendering of the original subject.
This process produces images where the textures and structures and overall form of the subject grab the attention rather than its colour.
The greatest challenge is in fact lighting the subject so as to not have really bright highlights from wet and other reflective surfaces.