This is best done through a filter perforated at its apex by a pin-hole.
The existence of the pin-hole pupil is also a contraindication to its employment.
To sew a button on securely you should make a pin-hole where the button is to be placed.
A pin-hole Camera is another extremely simple yet extraordinarily interesting contrivance (Fig. 100).
A pin-hole or minute sand-crack in the soil-pipe, or a very slight defect in a joint, is far more dangerous than a trap.
Look through a pin-hole in a card at a uniform white surface as the white shade of an ordinary reading-lamp.
With the right eye look through the pin-hole, the left eye being closed.
The pin-hole got larger—blue lights lay along the sides of the tunnel.
The background for the pin-hole should be the sky or other bright surface.
The pin-hole camera is simply a light-tight box with a small aperture in one side.