Re: Grayscale perception
Re: Grayscale perception
- Subject: Re: Grayscale perception
- From: Ray Maxwell <email@hidden>
- Date: Mon, 05 Dec 2005 19:39:57 -0800
Mark Rice wrote:
One measure of this is the Munsell color test. I took it when I got my first
job in the photo lab business to see what my color discrimination was. It
consisted of 256 color chips, mounted on wooden circles. The examiner mixed
them up, and then asked the examinee to put them in order. They used subtly
different hues - light desaturated green to light desaturated cyan, for
instance. The differences between colors were VERY subtle.
Hi Mark,
I believe that you are referring to the Farnsworth-Munsell 100-Hue test.
See this URL for more information:
http://www.gretagmacbeth.com/index/products/products_color-standards/products_color-vision-tests/products_fm-100-hue-test.htm
One of the ironies of this test is that it contain something like 88
hues. I don't remember the exact number, but I know it was less than
100 hues. If you had 256 hues in this test no one would be able to
perform this test perfectly.
With 88 hues most people make 3 or 4 transpositions if they have good
color perception. The scoring is too complicated to go into in a short
note, however, any score below 70 is considered "normal" color vision.
The ability to distunguish small differences in color has to do with the
magnitude of the color change (hue, lightness, saturation) and the
physical size of each color patch that is adjacent to the next.
Everyone who has made smooth appearing gradients in Illustrator or
InDesign knows that the color change can get larger if the spacing is
smaller.
The magnitude of each unit in CIE Lab space, is supposed to be at the
threshold of a typical standard observer being able to distinguish a
difference.
When it comes to gray scales on reflective media, there are people that
will tell you that anything greater than 64 steps will appear smooth.
The bottom line is that it takes much less than 256 steps to make a
smooth gradient. I would suggest that it is between 64 and 100.
Ray
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