Spatial resolution

Spatial resolution is an imaging system’s ability to distinguish small, closely spaced features. It describes the finest spatial detail that the system can reliably represent.

Point spread function: The image formed by an imaging system from an ideal point source. Its width and shape show how the system blurs fine spatial details.
Spatial frequency: The number of repeating spatial cycles per unit distance, such as alternating light and dark bands. Fine features correspond to higher spatial frequencies, which systems transfer less effectively.
Optical microscopy: Microscopy that uses visible or near-visible light and lenses to magnify small objects. Microscopists assess the smallest structures distinguishable through the objective and imaging chain.
Magnification: The ratio between an image’s apparent or recorded size and an object’s actual size. Magnification enlarges displayed features but does not guarantee that unresolved details become distinguishable.
Modulation transfer function: A measure of how an imaging system transfers contrast at different spatial frequencies. It quantifies how strongly the system preserves fine patterns as their spacing shrinks.
Contrast: The difference in intensity or color between parts of an image or scene. A feature may be spatially present yet indistinguishable when its contrast is too low.
Medical imaging: Techniques that create images of the body for diagnosis, monitoring, or research. Diagnostic detail is measured differently across modalities and must be balanced against noise and exposure.
Image sharpness: The perceived crispness of edges and fine transitions in an image. Sharpening can increase apparent crispness without restoring detail lost during capture.
Nyquist–Shannon sampling theorem: A theorem specifying the sampling rate needed to reconstruct a band-limited signal without aliasing. It sets a sampling condition for representing detail, but does not remove optical blur.
Field of view: The extent of a scene visible through an imaging system. Resolution stated in physical units depends on how much scene area spans the image.

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