TIFF Tag GrayResponseUnit
| IFD |  | Image |
|---|---|---|
| Code | 290 (hex 0x0122) | |
| Name | GrayResponseUnit | |
| LibTiff name | TIFFTAG_GRAYRESPONSEUNIT | |
| Type | SHORT | |
| Count | 1 | |
| Default | 2 (hundredths of a unit) |
Description
The precision of the information contained in the GrayResponseCurve.
Because optical density is specified in terms of fractional numbers, this field is necessary to interpret the stored integer information. For example, if GrayScaleResponseUnits is set to 4 (ten-thousandths of a unit), and a GrayScaleResponseCurve number for gray level 4 is 3455, then the resulting actual value is 0.3455.
Optical densitometers typically measure densities within the range of 0.0 to 2.0.
The specification defines these values:
1 = Number represents tenths of a unit.
2 = Number represents hundredths of a unit.
3 = Number represents thousandths of a unit.
4 = Number represents ten-thousandths of a unit.
5 = Number represents hundred-thousandths of a unit.
LibTiff defines these values:
GRAYRESPONSEUNIT_10S = 1;
GRAYRESPONSEUNIT_100S = 2;
GRAYRESPONSEUNIT_1000S = 3;
GRAYRESPONSEUNIT_10000S = 4;
GRAYRESPONSEUNIT_100000S = 5;
For historical reasons, the default is 2. However, for greater accuracy, 3 is recommended.