Left: Current constraints on the z = 7 luminosity function. The data points and Schechter function fit are taken from an analysis of WFC3/IR imaging of the HUDF (McLure et al. 2009) and include ground-based measurements at the bright end from Ouchi et al. (2009). The yellow, blue and green shaded regions indicate the absolute magnitude ranges which the Wide, Deep and combined surveys will probe. The horizontal lines correspond to counting 10 objects, which is roughly the number needed to reduce Poisson noise below cosmic variance. Right: Current constraints on the z = 8 luminosity function. Points with error bars are from McLure et al. (2009), while the dotted curve is a fit to the z = 8 HUDF luminosity function from Yan et al. (2009). The solid curve is the Schechter function fit from z = 7 shifted to lower normalization by a factor of two.