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The effects of seeing on the photometric properties of elliptical galaxies and, in particular, on the |Dₙ-| and fundamental plane distance estimators are studied. A new family of functions for the analytical approximation of the point spread function (psf) is introduced and is shown to fit stellar images better than the widely used Gaussian and Moffat functions. Seeing effects are computed for circular mean surface brightness distributions using the R1/4 law and models with more and less prominent central cusps. A prescription to correct raw half-luminosity radii, Dn diameters, and surface brightnesses at and within Re given. It is shown that seeing effects become important for distant ellipticals | (cz 8000 km \, s^-1) |. Uncorrected |Dₙ-| or fundamental plane distances are systematically too high, leading to spurious negative peculiar velocities of the order of |1000 km \, s^-1| at a distance of |12 000 km \, s^-1|. The large negative peculiar velocities of the most distant clusters of the Faber et al. sample are reduced when seeing effects are taken into account, as is the scatter in the |Dₙ-| relation. Seeing corrections are small for galaxies included in the flow solutions of Lynden-Bell et al. (1988) and are unlikely to affect them.
Saglia et al. (Fri,) studied this question.