A better contrast sensitivity test.

For years, the only widely-known online visual contrast sensitivity (VCS) test was vcstest.com — a port of the printed FACT chart from the mid-2010s. It is the de facto reference in some patient communities (mold/CIRS, concussion recovery, MS-tracking), and it is also genuinely flawed: a nine-step contrast quantization with documented ceiling effects, no real per-device calibration, mandatory email signup, and a paywall after the first run.

The science underneath contrast sensitivity is solid and clinically useful. The implementation people actually use online is not. That gap is what this project exists to close.

VCS-Test is free, calibrated to your screen and viewing distance, runs on a phone, uses an adaptive psychophysical staircase (instead of the coarse FACT step ladder), and tells you what your curve does and doesn’t mean. The methodology and the source are open. If we get something wrong, we want it pointed out.

VCS-Test is built by a small team that thought the existing options were both medically real and badly executed. We are not a clinic. We make no medical decisions. We try to write about vision science the way we’d want it written for ourselves — with the sources cited and the uncertainty on the page.

We publish under the VCS-Test team name rather than a single author byline: the work is collaborative, and the science — not the messenger — is the point.