Determination of the r magnitude of the RGB tip. Left panel: de-reddened CMD for the indicated elliptical annulus. The two parallel dashed lines enclose the RGB stars selected to derive the luminosity function. The pair of horizontal segments mark the level of the tip, the vertical segment marks the average color at the tip. Upper right panel: LF of the RGB. The sharp cut-off corresponding to the TRGB is marked by a vertical segment. Lower right panel: Sobel filter response as a function of r magnitude. The peak corresponding to the TRGB is marked by a vertical segment.