A contact screen is a type of halftone screen used in photographic and printing processes, where the dots consist of slightly soft or unsharp halos. When placed over a photographic image during printing, it breaks the continuous tones into a pattern of dots, creating a halftone effect that allows photographs to be reproduced with varying tonal densities. Contact screens are commonly used in traditional printing, graphic arts, and photo reproduction, helping to achieve detailed, visually appealing images that maintain depth and gradation even in printed formats.