Root-mean-square continuum contrast δI_rms as a function of the Fried parameter R₀ at wavelength λ = 10827 Å. Dotted, dashed, and solid curves correspond to the telescope diameters 0.7, 1.5, and 4 m, respectively. The δI_rms contrast for observations affected only by the diffraction limit of the VTT(D = 0.7 m), GREGOR (D = 1.5 m) and EST/DKIST (D = 4.0 m) telescopes (no seeing effects) are indicated in the upper part of this figure. The vertical arrow in the lower right corner marks the δI_rms value for the “perfect” observations corresponding to the case of the original spatial resolution (no smearing caused by the telescope and seeing effects). The calibration curves for the determination of the Fried parameter R₀ were calculated using the radiative transfer formal solution for the continuum intensity in the chosen 3D snapshot model of Rempel (2014).