Question

Why are surface of pinhole camera blackened

Answer 1

A pinhole camera is still a camera. On the inside, after the light has passed through the pinhole or lens, it has the opportunity to bounce off the sides of the camera and ruin the image.

Imagine being in a movie theater, with the projector representing the pinhole, and the screen representing the film inside the camera.

In a real movie theater, the image is carefully projected so it only hits the screen and not the sides of the theater or the ceiling, but in a real camera, the lens faces the outside world instead of a rectangle projector gate and rectangle piece of film or projector electronics. The outside world image is a giant circle that hits everything in our theater. If the walls were a bright color, or worse, something shiny like a mirror, the image projected onto them would bounce back into the screen, reducing contrast, and adding reflections. The brighter the walls, the worse the reflections.

Painting the inside of the theater black would drastically cut down on these problems. And it works exactly the same way inside your pinhole camera.

Answer 2

Explanation:

Light from the object goes through the pinhole and produces an inverted image in full colour on the screen. This is because only light from one point on the object can reach a given point on the screen. ... You should notice that the inside of the pinhole camera is painted black to stop unwanted reflections inside