The most widely spread application of energy filtering transmission electron microscopy (EFTEM) is the determination of elemental distributions in analytical investigations. The new EFTEM techniques are based on data acquisition by electron spectroscopic imaging (ESI), which offers the advantage of fast two-dimensional recording of the inner-shell loss intensities. In a more general framework, the new ESI methods and the standard PEELS technique both aim at exploring the same three dimensional data space. This data space is represented by the spatial coordinates x, y and the energy loss ΔE and the resulting intensity distribution I(x,y,ΔE) is the quantity which is evaluated. It is intuitively clear, that acquiring more than just three consecutive ESI images gives us the possibility to get quantitative information about the spectra and the shape of the ionization edge. The information on the EEL spectrum can be extracted from a series of ESI images for each individual pixel or, by integrating over corresponding pixels, for a given image area and can be quantified by applying standard EELS quantification techniques.