How is spatial resolution measured?

How is spatial resolution measured?

• A. lp/mm (line pairs per millimeter)
• B. dpi
• C. PPI
• D. Bits per pixel

Answer: (A)

Spatial resolution is about how finely a picture can hold detail—the smallest features you can still distinguish. The standard way to quantify this in imaging is line pairs per millimeter. A line pair is one dark line and one light line; if you can resolve a certain number of line pairs in every millimeter, you can separate features as small as about 1/(2 times that number) millimeters. That unit directly measures how finely the system can differentiate adjacent structures, which is what you care about when judging sharpness and detail. Dpi and PPI describe how densely dots or pixels are arranged on a page or on a screen, which is about sampling or display density rather than the optical ability to resolve fine details. Bits per pixel, meanwhile, tells you how much color or gray levels a image can store, not how much spatial detail it can convey. So line pairs per millimeter is the appropriate measure of spatial resolution.

Spatial resolution is about how finely a picture can hold detail—the smallest features you can still distinguish. The standard way to quantify this in imaging is line pairs per millimeter. A line pair is one dark line and one light line; if you can resolve a certain number of line pairs in every millimeter, you can separate features as small as about 1/(2 times that number) millimeters. That unit directly measures how finely the system can differentiate adjacent structures, which is what you care about when judging sharpness and detail.

Dpi and PPI describe how densely dots or pixels are arranged on a page or on a screen, which is about sampling or display density rather than the optical ability to resolve fine details. Bits per pixel, meanwhile, tells you how much color or gray levels a image can store, not how much spatial detail it can convey. So line pairs per millimeter is the appropriate measure of spatial resolution.