  We present a new method to estimate shear measurement bias in image
simulations that significantly improves the precision with respect to current
techniques. Our method is based on measuring the shear response for individual
images. We generated sheared versions of the same image to measure how the
galaxy shape changes with the small applied shear. This shear response is the
multiplicative shear bias for each image. In addition, we also measured the
individual additive bias. Using the same noise realizations for each sheared
version allows us to compute the shear response at very high precision. The
estimated shear bias of a sample of galaxies is then the average of the
individual measurements. The precision of this method leads to an improvement
with respect to previous methods concerned with the precision of estimates of
multiplicative bias since our method is not affected by noise from shape
measurements, which until now has been the dominant uncertainty. As a
consequence, the method does not require shape-noise suppression for a precise
estimation of shear multiplicative bias. Our method can be readily used for
numerous applications such as shear measurement validation and calibration,
reducing the number of necessary simulated images by a few orders of magnitude
to achieve the same precision.
