Hacker News Reader

Comment by gdubs | Hacker News Reader

When I was in college I spent a summer abroad at an art school in the south of France. It was a medieval village, and so instead of dorms everyone was scattered in various places throughout this village on a hillside.

Anyway, a couple of our classmates turned their entire room into a pinhole camera — a “camera obscura”, where the image of the whole valley was projected upside down on the wall.

It was pretty magical being inside of that.

View on HN

I accidentally turned the bedroom of an apartment I once lived in into a camera obscura. There was an annoying streetlight outside and I wanted it darker at night, and the view was only of a parking lot, so I blocked off the window with a big piece of plywood, but it was about 1 inch too short, and the blinds behind it left also left about 1 inch uncovered, so there was about a 1 inch by 1 inch opening left uncovered. And funny enough, I didn't lose the view of the parking lot, as it was projected upside down on the opposite wall.

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.

https://ibb.co/Lt60R7v

That's incredible!

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).

I think a useful term is "circle of confusion".

http://fslashd.com/2015/04/circles-of-confusion/

http://www.villageinframe.com/how-big-should-the-hole-be-in-...

This is a useful image. https://qph.fs.quoracdn.net/main-qimg-e92438d691243116d52f99...

It’s always there in the same way the Mona Lisa is always there on a wire sheet of paper, and just needs the extra spectrum masked out with paint.

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.

Those are amazing. My 1st year drawing teacher at RISD, Nicholas Evans-Cato (http://www.georgebillis.com/nicholas-evans-cato.html), taught us how to draw using cameras. We built our own camera obscuras from cardboard (about the size of a watermelon) and then made landscape paintings by looking at the image projected inside the camera as opposed to looking at the landscape directly.

With his mentorship I then got into other "primitive photography" methods like pinhole cameras. My favorite thing I made was a camera that had a vertical slit, as opposed to a pinhole, and a gear system that would pull 35mm film across the slit as the camera was rotated on a base. It was effectively a panoramic camera, but the cool thing is you could follow moving objects like cars and stretch them out.

RISD campus: https://i.imgur.com/VoONn1W.jpg

Stretched out cars: https://i.imgur.com/Gm6LMRE.jpg

See how on the far right, the front wheel of the minivan is a regular circle while the back is a long oval.

That was a very fun hobby, I expect to pick it up again when I have more free time.

Not sure if it’s apocryphal or not, but I remember hearing that that was how Vermeer painted.

Tim's Vermeer.

Ha, that's awesome. I will certainly be trying the moving slit trick on my slr in long exposure mode.

Weren't some of the sequences in 2001 shot similarly? https://en.m.wikipedia.org/wiki/Slit-scan_photography

If so, that's really cool and I didn't know that! Thanks for the link.

A Finnish company makes these kits for just that: https://bonfoton.com/

A few lifetimes ago I had a tiny apartment on a busy street in Brooklyn. I slept all hours so I had cardboard over my bedroom windows. There was a hole in the cardboard that on some days with the right light ended up projecting the busy street into my room. It was pretty amazing to hear all the sounds of a busy Brooklyn street below and watch it play out upside down on my dresser.

I accidentally did that in a projection room with a friend when I was aged about 10.

We blocked up the projection hole but missed a bit. Turning round to the see the hall outside projected upside down on the back wall was one of the most magical bits of serendipitous learning I have ever experienced.

There are quite a few historical camera obscura. Examples:

https://www.torretavira.com/en/what-is-a-camera-obscura/#jp-... (uses a mirror to project an image on a table surface, and allows one to rotate the tower containing the pinhole. Uses a lens, so this is a camera obscura, but I’m not sure whether to call it a pinhole camera)

https://en.wikipedia.org/wiki/Camera_Obscura,_Edinburgh

There's on in Santa Monica, California, as well[0]. Tourists walk by it all the time and probably just think it's a café with a funky name.

[0]https://www.santamonica.gov/arts/camera-obscura-art-lab

San Francisco too! The hours are a bit of a mystery to me, but one day I saw someone in the booth collecting entrance fees and finally got to go inside. Probably will have to wait until after covid to go inside again though. https://en.m.wikipedia.org/wiki/Camera_Obscura_(San_Francisc...

I visited this town! SCAD has done a great job and the students were lovely. What a magical place to study abroad.

It's camera obscura, not obscure.

Thanks - typo: fixed.

Reply on news.ycombinator.com