Each star variance ${\sigma }_{R,i}^2(k,R)$ as a function of field size R (dots; sizes are proportional to star brightness) for each reduction mode, their average $⟨{\sigma }_{R,i}^2(k,R)⟩$ for each R (large circles), fit functions Eq. (36) (solid), and the DIM variance ${\sigma }_{\mathrm{F}}^2(k,R)$ (Eq. (26)) based on the atmospheric model (dashed lines). For better visualization, the plots for each k > 6 are shown with a negative offset. The dots are dispersed horizontally for different star fields.