Editing Image resolution (section)

===Spatial resolution===
{{Main|Spatial resolution}}
{{Further|Focus (optics)}}

The terms blurriness and sharpness are used for digital images but other descriptors are used to reference the hardware capturing and displaying the images.

Spatial resolution in radiology is the ability of the imaging modality to differentiate two objects. Low spatial resolution techniques will be unable to differentiate between two objects that are relatively close together.
[[File:1951usaf test target.jpg|thumb|right|250px|The [[1951 USAF resolution test chart|1951 USAF resolution test target]] is a classic test target used to determine spatial resolution of imaging sensors and imaging systems.]]
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| footer=Image at left has a higher ''pixel count'' than the one to the right, but is still of worse spatial resolution.
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| image1=Kostas Martakis - blurred.jpg
| width1=200
| image2=Kostas Martakis 1.jpg
| width2=200
}}

The measure of how closely lines can be resolved in an image is called spatial resolution, and it depends on properties of the system creating the image, not just the pixel resolution in [[pixels per inch]] (ppi). For practical purposes the clarity of the image is decided by its spatial resolution, not the number of pixels in an image. In effect, spatial resolution is the number of ''independent'' pixel values per unit length.

The spatial resolution of consumer displays ranges from 50 to 800 pixel lines per inch.  With scanners, [[optical resolution]] is sometimes used to distinguish spatial resolution from the number of pixels per inch.

In [[remote sensing]], spatial resolution is typically limited by [[diffraction limit|diffraction]], as well as by aberrations, imperfect focus, and atmospheric distortion. The [[ground sample distance]] (GSD) of an image, the pixel spacing on the Earth's surface, is typically considerably smaller than the resolvable spot size.

In [[astronomy]], one{{who|date=February 2025}} often{{when|date=February 2025}} measures spatial resolution in data points per arcsecond subtended at the point of observation, because the physical distance between objects in the image depends on their distance away and this varies widely with the object of interest.  On the other hand, in [[electron microscopy]], line or fringe resolution is the minimum separation detectable between adjacent parallel lines (e.g. between planes of atoms), whereas point resolution is instead the minimum separation between adjacent points that can be both detected ''and interpreted'' e.g. as adjacent columns of atoms, for instance.  The former often helps one detect periodicity in specimens, whereas the latter (although more difficult to achieve) is key to visualizing how individual atoms interact.

In Stereoscopic 3D images, spatial resolution could be defined as the spatial information recorded or captured by two viewpoints of a [[stereo camera]] (left and right camera).