Calculate lens and room dimensions for immersive projections
Distance from the window (lens) to the projection surface.
How far away is the view? (e.g., tree, building)
How tall is the object?
Required Lens Focal Length:
3000 mm
Or Lens Power:
+0.33 Diopters
Tip: You can buy "Close-up Filters" or reading glasses with this diopter strength.
Image Size
30.0 cm
Magnification
0.0300x
For a 10m tall object at 100m distance.
⚠ Image will be inverted (upside down).
🎯 A Simple Example: Turning Your Bedroom into a Camera
You have a spare bedroom that is exactly 3 meters deep (from the window to the opposite wall). You want to darken the room and project the beautiful garden outside onto that back wall. What kind of lens do you need to buy to make the image sharp?
Just do this:
1️⃣ Select "🏠 I have a Room (Find Lens)".
2️⃣ Set "Units" to Metric and "Room Depth" to 3 meters.
3️⃣ Look at the "Required Lens Focal Length": it says 3000mm.
4️⃣ Look at the "Lens Power": it says +0.33 Diopters.
5️⃣ Go to an optical shop or search online for a "+0.33 Diopter" or "3000mm focal length" convex lens. (Tip: Very weak reading glasses or a specific "close-up" filter works well).
Pro tip: The larger the lens diameter, the brighter the image, but the "thinner" the area that will be in focus. A lens about 50-75mm (2-3 inches) wide is usually perfect for a room-sized projection!
Data Source: Natural Magic (Giambattista della Porta, 1558) • Public domain • Solo-developed with AI
The Camera Obscura (Latin for "dark chamber") is the ancestor of all modern photography. In 1558, Giambattista della Porta popularized the device in his book Magia Naturalis, describing it as a tool for artists and philosophers to observe the world.
Light travels in straight lines. Rays from the top of a tree travel down through the lens to hit the bottom of your wall, while rays from the roots travel up to hit the top. This geometric crossing at the "nodal point" of the lens creates a perfectly inverted, full-color moving image of the outside world.
Today, turning a spare bedroom into a giant Camera Obscura is a popular DIY project. By darkening a window completely and leaving just a small hole for a simple meniscus lens (like a spectacle lens or a cheap magnifying glass), you can project the entire street scene onto your walls. This tool helps you match the lens focal length to your room's depth to ensure the projection is in focus.
I tried to make a camera obscura box once. I fit perfectly inside. The image was great, but I couldn't catch the birds projected on the wall. 0/10 very frustrating. 🐈