Flikipedia A branching dictionary of the moving image

resolution

noun

The amount of fine spatial detail an image can render — how closely two points can lie and still be distinguished. In digital capture it is stated as a pixel count; in film it is measured as a limit of resolving power.

Origin From Latin resolutio, "a loosening, unfastening," from resolvere ("to loosen, resolve"); the optical sense of separating, or "resolving," two close details into distinct points developed in the physics of optical instruments in the nineteenth century.

  1. Optics The degree of fine spatial detail an imaging system records or displays, set by the smallest separation between two features that remains distinguishable rather than merging into one.

  2. Digital In digital imaging, the number of discrete picture elements across the frame, quoted as horizontal by vertical pixels or by a shorthand for the approximate horizontal count, such as 2K, 4K, or 8K. a 4K master with a pixel grid roughly 4,096 wide

  3. Film In photographic recording, the resolving power of a film or lens, expressed as the number of line pairs per millimeter that can be reproduced as separate lines.

Measuring spatial detail

Resolution describes how much fine detail an image holds — the point at which two neighboring features can no longer be told apart and blur into one. It is a property of a whole imaging chain, not of any single component: the lens that forms the image, the medium that records it, and any later sampling or display all impose their own limits, and the coarsest of them governs the result.

In digital capture the measure is a pixel count: the number of picture elements across the frame, written as width by height or by a rough shorthand for the horizontal figure. 2K denotes roughly two thousand pixels across, 4K roughly four thousand, and 8K roughly eight thousand, with each step approximately doubling the pixel dimensions in both directions. On photographic film, where there is no fixed grid, the equivalent quantity is resolving power, measured in line pairs per millimeter (lp/mm) — the finest alternation of light and dark lines the emulsion and lens together can reproduce as separate.

The limit set by grain

Film’s resolving power is bounded by the size and distribution of the developed silver or dye clumps that form the image. Because these grains are discrete and randomly placed, detail finer than the grain structure cannot be recorded; a faster, more sensitive stock generally has larger grain and therefore lower resolving power, while a slow, fine-grained stock resolves more. The physical area of the recording also matters: a larger film gauge spreads the same scene over more emulsion, so a given grain size subtends finer detail and the frame resolves more overall. On an image sensor the analogous ceiling is the spacing of the photosites, though as below the raw count is not the whole story.

Pixels versus perceived sharpness

A high pixel count does not by itself guarantee a detailed picture. Perceived sharpness depends on how much genuine detail reaches the sensor and how it is processed. A lens that cannot resolve fine detail limits the image before it is sampled, so pixels record blur rather than information. Sampling a continuous image onto a discrete grid can also introduce aliasing, and on a single-chip color sensor each photosite captures only one color, so full-color detail is reconstructed by demosaicing — an interpolation that yields effective resolution below the nominal pixel count. Two cameras quoting the same figure can therefore differ visibly in the detail they deliver.

Spatial and temporal resolution

Resolution in the sense above is spatial — detail within a single frame. Moving images have a second axis, temporal resolution, which is how finely time is sampled: the frame rate, or number of frames recorded per second. The two are largely independent. A sequence may hold great detail in each frame yet sample motion coarsely, producing judder or strobing on fast movement, or sample time finely while each frame is soft. Both contribute to the total information a moving image carries, and each can be traded against the other within the limits of a recording medium or transmission channel.

See also

  • image sensor— The electronic component that captures a digital image, converting light into electrical charge at a grid of photosites — the digital counterpart to photographic emulsion.
  • film gauge— The width of a strip of photographic film, measured in millimeters, and by extension the format defined by that width together with its perforations and frame dimensions.
  • photographic film— A flexible strip coated with a light-sensitive emulsion that records an image as a pattern of developed silver or dye.
  • lens— The optical element or assembly that gathers light and forms an image on photographic film or an electronic sensor, characterized chiefly by its focal length and its maximum aperture.

Sources

  1. Society of Motion Picture and Television Engineers (SMPTE), digital cinema mastering standards
  2. Digital Cinema Initiatives (DCI), “Digital Cinema System Specification”
  3. Ray, “Applied Photographic Optics”

Last revised: September 18, 2026