Ishihara Plates Explained

The Ishihara test comes in editions of 38, 24 and 14 plates, and its plates do different jobs: from a demonstration plate everyone reads to plates that only colour-blind people can see.

What an Ishihara plate is

An Ishihara plate is a circle filled with dots of different sizes. A figure, usually a one- or two-digit number, is drawn in dots of one set of hues and the background in another. The two sets look clearly different to typical colour vision and alike to red-green colour-deficient vision.

How many plates are in the Ishihara test?

The full test has 38 plates. The 24-plate and 14-plate editions are shorter versions for screening.

Edition	Plates	Includes tracing plates
Full edition	38	Yes
Standard edition	24	Yes
Concise edition	14	Yes

Types of Ishihara plates

Each image below is one of our own plates showing the same idea.

Example of a Demonstration plate — **Demonstration plate**Readable by everyone. It explains the task and spots people who aren't following it.

Example of a Transformation plate — **Transformation plate**Typical vision reads one number; red-green deficient vision reads a different one.

Example of a Vanishing plate — **Vanishing plate**Typical vision reads the number; it disappears for red-green deficient vision.

Example of a Classification plate — **Classification plate**Two digits: red-weak vision sees one, green-weak vision the other. Used to tell protan from deutan.

Example of a Tracing plate — **Tracing plate**A path or shape instead of a number, for children and people who can't read numbers.

Example of a Blue-yellow plate — **Blue-yellow plate**Not part of the Ishihara test, which only screens red-green. Our test adds these to catch tritan deficiency.

Numbers, shapes and paths

The main plates use numbers. People who can't read numbers, including young children, follow winding paths across the plate with a finger or a brush instead. There is no standard Ishihara edition with letters or animals; tests with shapes and pictures are separate tests designed for children.

Why online Ishihara plates look different

Images of the printed plates on websites are scans of a copyrighted book. Scanning and screens change the colours, so the plates may not work as designed. Purpose-built screen tests, like ours, calculate their colours for screens instead.

Plate questions

What does the first Ishihara plate show?

The first plate in every edition is a demonstration plate that everyone, including colour-blind people, should read. It shows the person how the test works and checks they understand it.

Why do I see a number where others see none?

That is a hidden-digit plate. It is designed so that red-green colour-deficient vision picks out a number that typical vision misses.

Are all Ishihara tests the same?

The editions share plates but differ in length. Online copies vary a lot in colour quality, so two "Ishihara tests" on different websites can give different results.

Try our plates for yourself.

Take the colour blind test