retina images are NEGATIVES made IN a CAMERA
sun prints are contact prints or photograms.
the images are ephemeral, they are not light safe, they usually turn whtie if fixed
they usually can not be developed or they turn black from the long exposure.
they can be made with dektol soaked paper, and sometimes loolk like they are COLOR photos, not BLACK and WHITE.
there are ways to fix them, but its a lot of trouble so i don’t bother.
EVERY image that i have made is the result of a copying an original
with SCANNER and using PHOTOSHOP.
after the image is scanned, i treat it like any other negative.
invert ( postive>negative or neg>positive)
levels to adjust contrast since they get damaged/degrade from the scanner
cropping /straightening out since i can’t put them perfectly in the scanner,or they were made with a camera i can’t compose with
desaturating/tinting / colorizing i remove tone of the image and add color to make it more like a color image, or painting or something else
i call them retina prints after niepce’s experiments with silver chloride paper
i don’t use silver chloride paper, but made with modern materials, handmade materials.