We show that an extremely accurate tone reproduction curve (TRC), insensitive to noise in the printer and the media, can be measured using a scanner. In the scannerbased approach, two patterns are written. The first contains as many as 15,000 extremely small patches of the 256 addressable gray levels randomly placed on paper. The random placement averages over the noise and the mean of each patch gives an estimate of the TRC. The second pattern consists of 256 narrow strips with a high spatial frequency modulation between two adjacent gray levels for each strip. The scanner response at the modulation frequency for each strip gives the change in gray level between each halftone. The absolute values of the TRC from the first measurement are adjusted to best agree with the slope measurements, resulting in a highly accurate TRC measurement.