Section 3.7.2.3. Intensities

Data items in this category are as follows:

ARRAY_INTENSITIES

The bullet () indicates a category key. The arrow () is a reference to a parent data item.

The relationship between the data values for individual image elements and the number of incident photons can be complex. The data items in the ARRAY_INTENSITIES category provide information about this relationship. The value of _array_intensities.linearity states the type of relationship, and the values of _array_intensities.array_id and _array_intensities.binary_id identify the array structure and the image being discussed. The other items are used in different ways depending on the relationship. If the value of _array_intensities.linearity is raw, then the image elements hold uninterpreted raw data values from the detector, e.g. for calibration. If the value of _array_intensities.linearity is linear, then the count in an image element is proportional to the incident number of photons by the value of _array_intensities.gain. The standard uncertainty (estimated standard deviation) of the gain may be given in _array_intensities.gain_esd. The value used for this should be estimated from a good understanding of the physical characteristics of the experimental apparatus. If the value of _array_intensities.linearity is offset, then the value of _array_intensities.offset should be added to the image element value. If the value of _array_intensities.linearity is scaling, scaling_offset, sqrt_scaled or logarithmic_scaled, the necessary scaling factor is given by the value of _array_intensities.scaling. In all cases, the scaling factor is applied to the image element value before the other operations are applied. In the first case, only simple scaling is used. In the second case, the value of _array_intensities.offset is added after scaling. In the third case, the scaled value is squared. In the final case, 10 is taken to the power given by the scaled value.