Image resolution

Image resolution measures the spatial detail represented in an image, commonly by its pixel dimensions or the number of pixels per unit length.

Pixel: A pixel is a discrete sample in a digital image or the smallest addressable element of a display. Image dimensions count pixels along each axis.
Nyquist–Shannon sampling theorem: The Nyquist–Shannon sampling theorem states the conditions under which a band-limited signal can be reconstructed from samples. It sets a sampling-rate condition for representing spatial detail without aliasing.
Digital camera: A digital camera captures images with an electronic sensor and stores them as digital data. Sensor sampling and optics jointly determine captured detail.
Megapixel: A megapixel is one million pixels, a unit commonly used to describe digital image size. Megapixel counts summarize dimensions but do not specify sharpness or print density.
Image sampling: Image sampling converts a continuous scene or signal into discrete spatial measurements. Sampling determines which spatial details can be represented in a digital image.
Aliasing: Aliasing occurs when sampling makes distinct signal patterns indistinguishable, producing false frequencies or visual artifacts. Insufficient sampling can make fine image detail appear incorrectly.
Image sensor: An image sensor converts incoming light into electrical signals used to form a digital image. Its sampling grid contributes to an image's pixel dimensions.
Dots per inch: Dots per inch measures the number of printer dots placed in one inch. Printer dots are not the same as image pixels per inch.
Spatial frequency: Spatial frequency describes how rapidly image intensity varies across space, often in cycles per unit distance. Resolution limits the finest patterns an image can represent.
Optical resolution: Optical resolution is an imaging system's ability to distinguish nearby points as separate. A sensor's pixel grid cannot recover detail the optics fail to resolve.

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