Image Sensor Format

Image sensor format, sometimes referred to as “optical format” or “sensor size”, refers to the shape and size of the image sensor in a digital camera. The image sensor format is usually listed in the camera’s specifications and is required knowledge for selecting appropriate macro lenses and microscope adapters. There are two ways image sensor format can be described: inch-based format and APS format.

The inch-based image sensor format originated in the 1950’s and stems from the physical size of the vidicon tube sensor used in cameras at that time. The outside diameter of the vidicon tube was equal to 1” and the imaging area of the tube was 16mm diagonal. The sensor was commonly referred to as a 1” sensor and shortly thereafter it was commonly known that a 1” sensor had an imaging diagonal of 16mm. This resulted in the seemingly odd image sensor inch format: 1” = 16mm. This format standard survived the conversion to solid state image sensors (CCD and CMOS sensors) even though the corresponding vidicon tube was gone. The 1” = 16mm conversion factor allows the quick calculation of the modern day inch format sensor diagonals seen in the table below.

Inch-Based Sensor Formats

When image sensors exceed 4/3”, the APS (Advanced Photo System) format standard is used to describe the size of sensors instead of the inch-based format. The APS measurement system originates in 35 mm SLR & DSLR camera standards. Common APS formats are listed in the table below.

APS Sensor Formats