Section 11.2.1. Introduction

Data integration refers to the process of obtaining estimates of diffracted intensities (and their standard deviations) from the raw images recorded by an X-ray detector. As two-dimensional (2D) area detectors are almost universally used to collect macromolecular diffraction data, only this type of detector will be considered in the following analysis.

When collecting data with a 2D area detector, a decision has to be taken about the magnitude of the angular rotation of the crystal during the recording of each image. Two distinct modes of operation are possible: the rotation per image can be comparable to, or greater than, the angular reflection range of a typical reflection (coarse φ slicing), or it can be much less than the reflection width (fine φ slicing). The latter approach allows the use of three-dimensional profile fitting and, providing that the detector is relatively noise-free, improves the quality of the resulting data by minimizing the contribution of the X-ray background to the total measured intensity. However, there are significant overheads associated with recording, storing and processing the relatively large number of images that are required. Three-dimensional profile fitting is described in Chapter 11.3 and will not be discussed here.