F814W imaging in COSMOS (Koekemoer et al. 2007) and CANDELS (when available, Koekemoer et al. 2011) of the measured sizes for three galaxies in each of four increasing redshift bins from z ~ 2.4 to z ~ 4.1 (top to bottom) in our sample. The green contours show a smoothed version of the segmentation map of the galaxy at the defined threshold, which translates into T₁₀₀ from Eq. (6) measured at k_p = 1.0. The black ellipses are constructed from the values of r_e,b/a and θ_PA derived from GALFIT for those galaxies. The parametric and symmetric 2D profile fitting with GALFIT fails to properly account for the complex irregular morphology when deriving the size of galaxies at these redshifts, while the non-parametric method presented in this paper is able to derive more realistic sizes.