Ratio of the uncertainty in the photometric parallaxes to the TGAS catalog errors for Cepheids in our sample, as a function of apparent G magnitude. The median value of the ratio is 0.072, and the maximum is 0.24, indicating that the photometric errors are negligible in comparison to the TGAS measurement error. The photometric errors are based on an assumed width of P/L relation of 0.08 mag, which combines its intrinsic width with the uncertainties in ground-based magnitudes. The strong correlation is a distance effect: the brighter Cepheids are typically closer, so that a given fractional error in distance (deriving from a constant error in distance modulus) translates to a larger uncertainty in the photometric parallax.