Here are some gray level gratings with low average (LA) and high
average (HA) luminance and low (LF) and high (HF) spatial
frequency. Furthermore the gratings can have high (HC) or low (LC)
contrast.
LC
HC
HA
LF
HA
HF
LA
LF
LA
HF
Chromaticity Gratings
From Red to Green
From Blue to Yellow
LF
HF
A Moving Grating
Want to See Your Modulation Transfer Function
Grating detection depends on the grating's spatial frequency and its
modulation depth. A function which describes the transfer of the
physical description of a grating into perceived properties may be
called "visual modulation transfer function", a term which is used in
systems theory to describe linear systems. A nice approximation to
ones own visual modulation transfer function can be seen when looking
at a grating whose spatial frequency increases in
the horizontal direction and whose modulation depth decreases in the
vertical direction.
Look at the image and try to see the hull of the area which contains
some intensity modulation. The horizontal axis corresponds to a log
frequency scale while the vertical axis corresponds to decreasing
modulation and thus to sensitivity. The apparent border between
visible and invisible modulation corresponds to your own visual
modulation transfer function.
Where do the gratings come from?
All the gratings on this page have been generated by the program
MVG from the author's
PXL library. The gratings were generated by
using MVG's -G option and then loading the resulting GIF files into
Alchemy Mindworks' GIF Construction Set Animation Wizard.
