|Exif TIFF Tag FocalPlaneResolutionUnit|
TIFF Tag Reference
TIFF Tag FocalPlaneResolutionUnit
Indicates the unit for measuring FocalPlaneXResolution and FocalPlaneYResolution.
This value is the same as the ResolutionUnit. Thus, the defined values are:
1 = No absolute unit of measurement.
The FocalPlaneResolution tags record the actual focal plane resolutions of the main image which is written as a file after processing instead of the pixel resolution of the image sensor in the camera. It should be noted carefully that the data from the image sensor is resampled.
These tags are used at the same time as a FocalLength tag when the angle of field of the recorded image is to be calculated precisely.