How to capture images of non-luminous objects?
The pinhole camera we looked at previously was constructed to capture the image of luminous objects, like the Sun. But for non-luminous objects like a distant tree or a pillar, we have to construct the pinhole camera in a different way.
The pinhole camera is now a rectangular box with a pinhole on one side and a translucent paper fixed as a screen on the other side, from where we will observe the image.
Pinhole camera
How does a pinhole camera work?
Suppose we are observing a distant tree with this pinhole camera. What we obtain on the screen is an inverted image of the tree.
This is because light travels in a straight line. The light from the bottom of the tree reaches the pinhole and onto the screen in a slanting manner. Same with the top of the tree. Hence the final image is an inverted tree.
Inverted image of a tree formed in a pinhole camera
Let us see the changes in the image when we modify our pinhole setting a little bit.
What happens when we change the position of the pinhole camera?
Case 1: Bringing the pinhole camera closer to the objects
The image becomes bigger and dimmer. This is because the light from the object gets spread on a wider area.
An enlarged image formed when the pinhole camera is brought closer to the tree
Case 2: Taking the pinhole camera farther from the objects
The image reduces in size and becomes brighter because the light is getting concentrated in a lesser area of the screen.
What happens when we increase the size of the pinhole?
The image of the tree becomes blurry because the increased pinhole size is allowing multiple light rays to enter the camera. These light rays form multiple images of the tree which makes the overall image distorted and blurry.
A blurry image formed when the pinhole size is increased
