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7.1 Overview of FOC Characteristics

Table 7.1 lists certain effects owing to the design of the FOC detector, optics, and electronics that afflict all FOC images and indicates whether the pipeline corrects for them. .

**Characteristics Corrected in Standard Pipeline**
Characteristic	Pipeline Corrected?
Nonlinearity and saturation	No
Geometric distortion	Yes
Flatfield residuals (i.e., blemishes, reseau marks, defects, and video effects)	No
Format-dependent sensitivity	Yes
Background noise	No
Filter-induced image shifts	No
Point spread function	No

The diagram below (Figure 7.1) describes where these various instrumental characteristics arise.

Figure 7.1: Sources of Instrumental Characteristics

The ideal calibration algorithm applies to the raw data the inverse transformation to that which converted the input image to the output image. Each step would apply the corrections in reverse order, starting with the nonlinearity correction. In practice, the individual components of the ideal transformation are not known accurately, so such a process is unrealistic. Therefore, some of these effects are addressed only partially in the pipeline while others are not corrected at all. The following sections describe the limitations of these calibrations and their effects on the uncorrected image characteristics.

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7.1 Overview of FOC Characteristics

Characteristic

Pipeline Corrected?

Figure 7.1: Sources of Instrumental Characteristics