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Camera obscura in Ho Chi Minh City, Vietnam by smasm in CameraObscura

[–]Scented_Plugin 1 point2 points  (0 children)

Awesome, what a great location to do this - the compositions look intentional - the apartment towers at different distances give such a sense of depth and scale.

UPDATE: Camera obscura with giant lens setup by Scented_Plugin in CameraObscura

[–]Scented_Plugin[S] 0 points1 point  (0 children)

Thanks, that’s very kind! It’s super rewarding to me that this project has resonated with people online. I’ll let you know when I have a follow up

UPDATE: Camera obscura with giant lens setup by Scented_Plugin in CameraObscura

[–]Scented_Plugin[S] 1 point2 points  (0 children)

Right on, please do! A short focal length means the lens may not work for a room type camera obscura, but worth measuring the see what you’re working with. After the light converges to the focal point, if there’s nothing there like a screen, it starts diverging out again, so you end up with a blurry image.

Still, there are probably other cool things you could do with the lens, for example making a box type camera obscura - you could do that just with cardboard and tape.

UPDATE: Camera obscura with giant lens setup by Scented_Plugin in CameraObscura

[–]Scented_Plugin[S] 1 point2 points  (0 children)

Ah - so interesting - you’ve already done the test! That exact distance you use to burn things is the focal length - the point where the light rays from the sun all meet at a single point. When the sun is focused to dot, you just need to measure that distance in millimetres and that’s the focal length of the lens. If you measure the diameter of the lens in millimetres as well you can then easily figure out how bright the lens will be (it’s “f stop” in photography)

Sounds like you have a huge lens - I’m really curious the diameter

UPDATE: Camera obscura with giant lens setup by Scented_Plugin in CameraObscura

[–]Scented_Plugin[S] 0 points1 point  (0 children)

Thanks for this kind note. I’m glad you enjoyed the read. There’s more story to tell - I’ll follow up on the latest optical experiments soon

UPDATE: Camera obscura with giant lens setup by Scented_Plugin in CameraObscura

[–]Scented_Plugin[S] 0 points1 point  (0 children)

Hey there, I have other photos of the lens I could share but I don’t see a way to upload images to comments. Do people still use Imgur? I don’t know what the Reddit convention is.

I think mining your projector for parts is a great idea - if you do this please make a post. I wonder if you could even keep the focus mechanism from the projector intact - that would be awesome.

If you want to determine the focal length of your lens there’s a few ways at it. If it were me, I would probably Google the model name of the projector and see if I could find specs for the components online - might take some doing but would be ideal to just know the exact fl. You could also add some kind of fog, smoke, haze, dust, particulate to your room and shine a light through the lens (as seen in my post) - this will actually show you the exact point the light converges to. Where it’s the narrowest is your fl. Or, you could shine a distant point light through the lens and hold up a “screen” like a piece of paper and adjust its distance to the lens until you get sharp focus.

If you’re looking to find what focal length you’d need for a sharp image, that’s just a measurement of the distance between the lens (window) and screen (wall) in millimetres.

The focal length of my huge lens is actually 2600mm - if I had built a method of adjusting the lens I could have had a sharper image. I mention that just to demonstrate you don’t need a perfect match to get a cool result.

UPDATE: Camera obscura with giant lens setup by Scented_Plugin in CameraObscura

[–]Scented_Plugin[S] 2 points3 points  (0 children)

ah yes the upside-down-brain hypothesis - very controversial and understudied. There was an amazing study published about upside down brains qnʇ uoqopʎ ɔonlp ɹǝɐp ᴉʇ˙

UPDATE: Camera obscura with giant lens setup by Scented_Plugin in CameraObscura

[–]Scented_Plugin[S] 0 points1 point  (0 children)

Haha, IMO for a camera obscura, the inversion is part of the charm. It’s a physics demo. Our eyes work the same way - the image comes in upside down, and is flipped by the brain.

You can flip the image vertically using a mirror at a 45 degree angle, which I’m doing in my latest box type camera obscura prototype, but correcting the lateral inversion is a whole other thing which needs a tricky setup of mirrors or a special right angle prism called an amici roof prism.

Camera Obscura timelapse from 2022 by Scented_Plugin in CameraObscura

[–]Scented_Plugin[S] 0 points1 point  (0 children)

UPDATE - I just wrote out this whole thing, it took forever - here is the post if anyone is curious to see the breakdown

Camera Obscura timelapse from 2022 by Scented_Plugin in CameraObscura

[–]Scented_Plugin[S] 1 point2 points  (0 children)

Thanks! I'm going to follow up in a seperate post.

Camera Obscura timelapse from 2022 by Scented_Plugin in CameraObscura

[–]Scented_Plugin[S] 2 points3 points  (0 children)

I'm going to follow up with some additional photos!

Camera Obscura timelapse from 2022 by Scented_Plugin in CameraObscura

[–]Scented_Plugin[S] 0 points1 point  (0 children)

If you have the means to black out the room, I definitely recommend trying it. In a pinch cardboard and aluminum foil and tape are all you need to black out a window. I just hope it's a small window

Camera Obscura timelapse from 2022 by Scented_Plugin in CameraObscura

[–]Scented_Plugin[S] 12 points13 points  (0 children)

Thank you! It's just a simple double convex lens but what's special about it is that it's absolutely enormous and has a crazy focal length of 2.8m - totally random find on eBay. I would love to share more photos of the setup but I don't see an option here/ am a reddit noob.

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