Image resolution is the level of detail in a photo or video. Film and digital cameras, printing, and projecting images require high-quality lenses for optimal resolution. Film reproduces light patterns, resulting in precise resolution, while digital images are made up of pixels. Enlarging an image does not increase its resolution and can reduce image quality. High-definition images are created by increasing pixel density.
Image resolution refers to the level of detail in a photographic or video image. It applies to creating images with film and digital cameras, reproducing images in print, and projecting images onto screens and monitors. In film photography, image resolution was determined by the size and quality of the film itself. The resolution of digital photography depends on the density of individual image components, called pixels. In both media, high-quality lenses are also required for optimal image resolution.
In all visual media, the ideal is to create an image that contains as much detail as its original source. For much of the 20th century, the motion picture format was vastly superior to television and video in this respect. This is because film reproduces the actual light patterns of an image, just like the eye does, whereas early video produced only an approximation. In the 21st century, digital video formats had reached a level of resolution that the naked eye could not distinguish from film images. This manifested itself in high-resolution cameras and camcorders, high-definition (HD) television screens, and digital effects and animation in big-screen movies.
Film cameras captured images by focusing light through a lens onto a moving or stationary recording surface, known as a frame or negative. The chemicals on this surface took on the exact shape of the light, resulting in a very precise image resolution. The resulting images could often be greatly enlarged, using film projectors or photographic enlargers, without appreciable loss of quality. For large-scale reproduction, photographers preferred a large negative; some fine art photographers used frames 10 times larger than the standard 35mm size. When the small frames were zoomed in, the chemical grains that make up the image could be seen, resulting in what was known as a grainy image.
Digital images, including images from movies that have been scanned into a computer, are made up of tiny squares of color called pixels, short for “picture elements.” Image resolution is determined by the number of pixels in a given area, indicated by measurements such as pixels per inch (PPI or ppi). Televisions and video monitors create images by projecting lines of light onto the screen. High-definition images in all of these media are created by increasing the density of pixels or lines. High resolution is also required for all images that will be published on a print medium.
Enlarging an image does not increase its resolution; in fact, this will make pixels or grain more noticeable, reducing image quality. This process was a key plot point in the influential 1966 film Blow-Up, about a photographer who finds evidence of a crime in the background of a photo. Spy movies and TV crime dramas often gloss over this fact by allowing the characters to enhance the image resolution more than is possible with ordinary software. The sci-fi cartoon Futurama once played on this by having a starship captain ask for an enlarged image to show fine detail. When told this wasn’t possible, he complained that it always worked on TV detective shows.
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