What is spatial resolution?
Since we know by now that each digital image is just the collection of pixels in 2D matrix format. Now we define spatial resolution as a term that refers to the number of pixels that are used to construct a digital image. When we say that a particular digital image is having higher spatial resolution than another image, it simply means that the higher spatial resolution image is composed of more pixels than the lower spatial resolution image for the same dimensions of the imaging part. It is important to note that we are talking about the same dimensions of both images.
Spatial resolution can determine the quality of an image and describe how detailed an object can be represented by the image. It has importance in medical images such as ultrasound tomography and CT scan.
How spatial resolution of a digitized image is different from brightness resolution in MATLAB?
A digital image is represented in the form of a 2D matrix of integers/floats, in which each element of the matrix represents pixel intensity. This intensity distribution of images depicted in the form of 2D matrices is called Spatial Domain. The intensity value depends on the bit-depth of the image. For example, if bit-depth is 8bit then pixel intensity can take values from 0 to 255.