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Re: Colour Vision




On 18.02.98 Rob at alegria.com wrote:

<are these tests self-administered, and are they via a print (reflective,
subtractive) medium?>

Both the Ishihara and 100 Hue Test are reflective/subtractive:-

On 18.02.98 tmagic at pop.interport.net wrote:

<The doctor quickly flipped through some book with opposite colors to check
for color blindness, but that was not a very finely tuned test.> - That sounds
like the Ishihara test.

Ishihara takes the form of a book with with coloured numbers printed on
speckled coloured backgrounds - it's the test that most people encounter at
one time or another to determine colour blindness (although that is rather a
vague term which, in fact, encompasses a number of different abnormalities).
The strange thing about Ishihara is that it's quite possible for some subjects
to pass all of the normal tests (ie discriminate the numbers from the
backgrounds that a normal subject would) and then go on the pass the abnormal
tests, too (ie discriminate the numbers in the tests designed to determine
what kind of colour blindness it is - after failing the normal tests - that
you exhibit).

The Farnsworth-Munsell 100 Hue Test involves ordering the progression of
little 'caps' - which look like lipstick lids - such that their hue changes
progressively between two fixed 'caps'. It is designed to be conducted under a
controlled and specified (at university we used something called a 'Verivide'
cabinet) lighting conditions and also has a specified method of tabulating
results which establish a standard deviation from the perfect, when conducted
on a large group of subjects. 

I'm not aware of any CRT display based test, Rob, but one may exist. It would
seem unlikely though, considering the limited colour gamut of colour CRTs.

I wouldn't want to give the impression that I'm any kind of expert on the
subject of colour vision but, if anyone is interested in finding out more
about the subject, a good place to start is R.W.G Hunt's 'The Reproduction of
Colour'. I would also imagine that Kodak have a wealth of information on the
subject tucked away somewhere.

That mandatory testing scheme though... never thought of that... come to think
of it, you could test prospective fighter pilots to determine if they could
see other 'planes and stuff before you let them fly - the possibilities are
endless!

regards,

Adrian Thomas
London, UK

---
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