  Achromatic, mean-modulated flicker (wherein luminance increments and
decrements of equal magnitude are applied, over time, to a test field) is
commonly used in both clinical assessment of vision and experimental studies of
visual systems. However, presenting flicker on computer-controlled displays is
problematic; displays typically introduce luminance artifacts at high flicker
frequency or contrast, potentially interfering with the validity of findings.
Here, we present a battery of tests used to weigh the relative merits of two
displays for presenting achromatic, mean-modulated flicker. These tests
revealed marked differences between a new high-performance liquid-crystal
display (LCD; EIZO ColorEdge CG247X) and a new consumer-grade LCD (Dell
U2415b), despite displays' vendor-supplied specifications being almost
identical. We measured displayed luminance using a spot meter and a linearized
photodiode. We derived several measures, including spatial uniformity, the
effect of viewing angle, response times, Fourier amplitude spectra, and
cycle-averaged luminance. We presented paired luminance pulses to quantify the
displays' nonlinear dynamics. The CG247X showed relatively good spatial
uniformity (e.g., at moderate luminance, standard deviation 2.8% versus
U2415b's 5.3%). Fourier transformation of nominally static test patches
revealed spectra free of artifacts, with the exception of a frame response. The
CG247X's rise and fall times depended on both the luminance from which, and to
which, it responded, as is to be generally expected from LCDs. Despite this
nonlinear behaviour, we were able to define a contrast and frequency range
wherein the CG247X appeared largely artifact-free; the relationship between
nominal luminance and displayed luminance was accurately modelled using a
causal, linear time-invariant system. This range included contrasts up to 80%,
and flicker frequencies up to 30 Hz.
