associated with the discreteness of the electron charge—whereas quantum photodetection theory is required for the SPDC case, owing to the nonclassical nature of its output state [@Erkmen2008Unified]. Nevertheless, to provide a unified development, we will employ quantum photodetection to characterize both pseudothermal and SPDC ghost imaging. We begin, in Sec. \[sec:Setup\], with the theoretical framework for our analysis. Here we will describe our models for the pseudothermal and SPDC sources, reflection from the target, atmospheric propagation, quantum photodetection, and image formation. In Sec. \[sec:ResCon\] we will derive expressions for the spatial resolution and image contrast for pseudothermal and SPDC ghost images, and in Sec. \[sec:SNR\] we will derive their respective signal-to-noise ratios (SNRs). Then, in Sec. \[sec:Comp\], we shall consider a computational ghost imager, in which the reference beam is calculated instead of measured [@Shapiro2008Comp]. Because the reference beam is not an optical field, we find it convenient in Sec. \[sec:Comp\] to employ the semiclassical theory. This section will also include a quantitative performance comparison between pseudothermal, SDPC, and computational ghost images formed in reflection. We conclude, in Sec. \[sec:Discussion\], with a discussion of our findings, and an assessment of the situations in which reflective ghost-imaging might have practical value.

