I stayed at a quirky hotel in Amsterdam where all of the rooms had different themes. The theme for this room was camera obscura. One wall had these large windows that had metal doors to totally seal out the light but the door in the middle had a small hole to make the camera obscura. The next morning we had a pretty cool shot of the buildings nearby. I hadn't ever actually seen a camera obscura before so I had no idea it looked as good as it does.
There was a really cool moment in an Nvidia RTX demo (rtx = hardware accelerated raytracing effecs), where they created and showed a camera obscura in the game Minecraft -- https://youtu.be/opCDN2jkZaI?t=432 (7:12 if the timestamp doesn't work).
Supposedly this was something the Nvidia devs were not necessarily expecting to see but happened to stumble upon it. In other words, it arose naturally from their treating light as physical rays rather than being programmed in, and if so I think that's pretty neat.
Is it fair to say that the image is always there, but lost in a wash of additional light, and that a camera obscura filters out the other light, revealing the image that is already there? Or does a camera obscura somehow shape the light in a new way to produce the image?
I might say that there are an infinite number of copies of the image always there, all washing each other out. Each is a slightly different image (each has a slightly different centre of projection, in the jargon). If your pinhole is infinitely small, you get an infinitely-weak shot of a single one of those images. As you enlarge the pinhole, you get a larger collection of images, all added together, so you get more total light, but a bit of blurriness (because the images you're adding are all just a touch different).
https://ibb.co/Lt60R7v