Vision · low-contrast demonstration
Explore how faint a symbol can look on your screen with a short, uncalibrated low-contrast demonstration.
A contrast sensitivity test examines how well you distinguish a target from its background as the difference in brightness decreases. This free online demonstration uses 12 gap-direction questions to show that idea on your own screen. It reports your answers, not a clinical contrast threshold, a normal or abnormal result, or a diagnosis.
Visual acuity asks how small a detail you can resolve. Contrast sensitivity asks how faint a target can become before you lose it against its background. A pale object against a pale wall illustrates the second challenge: the object can be large and still hard to pick out. Mars explains the distinction between shrinking letters and fading letters.
Choose the direction of a gap in a ring: up, right, down or left. If you cannot distinguish it, choose “Cannot tell.” There are 12 untimed rounds, with two rings at each of six display settings. The rings become fainter; their direction is randomized independently on every round and on each new run.
Use a steady viewing position, your usual screen-distance glasses or contacts, and both eyes. Keep brightness, browser zoom and orientation unchanged. After each answer, continue when you are ready. The recap shows how many directions matched at each stage, with no pass/fail cutoff. A correct guess is still possible, so two successful answers do not establish a visual threshold.
These methods present different targets and follow different procedures. The named tests have their own materials, settings and evidence; a score belongs to the method used to obtain it.
A gray pixel value does not specify the actual luminance leaving your screen. Display tone response and reflections influence the target you see; physical target size and distance also matter. FrACT’s developer documents size, distance and luminance calibration requirements for contrast testing. Our preparation tips do not perform that calibration. Read the FrACT calibration guidance.
See the idea in action. Experience a fixed-size symbol becoming fainter and review your actual responses.
No clinical threshold. This original exercise is unvalidated. It cannot produce a logCS score, classify eye health or determine the cause of a visual difficulty.
Bring everyday concerns to an eye exam. An answer count cannot explain trouble seeing faint objects. If your everyday vision is changing, discuss the change with an eye-care professional regardless of this recap.
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Last reviewed September 12, 2026. Educational information and an original, uncalibrated demonstration. The cited methods have their own validation; this exercise has not been clinically validated.