Photovoltaic (PV) collectors are usually deployed in a number of rows facing south (in the northern hemisphere) on horizontal or on inclined planes. The second and subsequent collector rows are subject to shading and masking (expressed by the sky view factor) by the rows in front. Shading affects the direct beam radiation [
1,
2] and masking affects the diffuse incident radiation on the rows [
3]. A design of PV fields must take into account the decrease in the incident radiation caused by these two effects and hence causing losses in the electrical energy generation. Shading of different kinds on PV modules is considered an adversary to PV systems and mitigating means were devised to reduce its effect, such as increasing the collectors’ row-to-row distance and including bypass diodes in the PV modules. Not much attention has been paid in the past to the masking phenomenon and its effect on the power loss of PV systems. In fact, the amount of masking on the collector varies along the collector width causing uneven incident diffuse radiation on the PV modules. The detrimental effect associated with masking has been addressed in a recent work which established the view-factor as an emerging topic of technical significance [
3]. The article deals with the effect of uneven diffuse incident radiation on the PV cells within the module caused by the effect of the local view factor along the module’s surface. The uneven diffuse radiation inflicts current mismatch between the strips of the module, manifesting by step formation on the I–V characteristic and affecting the output power of the module. The present study investigates the annual incident diffuse, direct beam and global radiation on the first and on the second row for optimized PV fields. An optimal design of a PV field may be formulated mathematically as a constrained optimization problem comprising of an objective function and a set of constraints usually multivariable and nonlinear in both the objective and constraint functions [
4,
5]. Based on this mathematical concept, optimal PV systems were formulated and studied in [
6,
7,
8]. These articles consider row shading and masking in the optimal designs and employ the isotropic diffuse radiation model. Articles dealing with optimal designs of PV systems for different objective functions and different optimization algorithms are mentioned in [
7]. The present study widened the optimal design of PV fields not dealt with in References [
6,
7] by including designs on inclined fields in Tel Aviv, Israel (latitude 32° N) with low diffuse radiation component and in Lindenberg, Germany (latitude 52.2° N) with high diffuse radiation component, for both horizontal and inclined fields. In addition, the effect of isotropic and anisotropic diffuse radiation models on the design is compared in the study. The study emphasizes the importance of the incident diffuse radiation (associated with the sky view factor) on the energy loss of the PV field. The energy loss due to shading and masking may be translated into de-rated power of the PV module and therefore has significant technical consequences for PV field designs.