  We revisit the impact of finite time responses of bolometric detectors used
for deep observations of the cosmic microwave background (CMB). Until now,
bolometer transfer functions have been accounted for through a two-step
procedure by first deconvolving an estimate of their Fourier-space
representation from the raw time-ordered data (TOD), and then averaging the
deconvolved TOD into pixelized maps. However, for many experiments, including
the Planck High Frequency Instrument (HFI), it is necessary to apply an
additional low-pass filter to avoid an excessive noise boost, which leads to an
asymmetric effective beam. In this paper we demonstrate that this effect can be
avoided if the transfer function deconvolution and pixelization operations are
performed simultaneously through integrated maximum likelihood mapmaking. The
resulting algorithm is structurally identical to the artDeco algorithm
introduced by Keih\"anen & Reinecke (2012) for beam deconvolution. We
illustrate the relevance of this method with simulated Planck HFI 143 GHz data,
and find that the resulting effective beam is both more symmetric than with the
two-step procedure, resulting in a sky-averaged ellipticity that is 64 % lower,
and an effective beam full-width-at-half-maximum (FWHM) that is 2.3 % smaller.
Similar improvements are expected for any other bolometer-based CMB experiments
with long time constants.
