Hue Tone and Saturation

[Jeffrey Hunt]

Hue Tone and Saturation

I have a question about the definition of color in gemstones inspired by Chrono in an earlier post. Specifically, the definition of Hue, Tone, and Saturation in the following link:

http://www.palagems.com/quality_4cs.htm#color

My question for the experts here - Is this generally accepted terminology for colored stones or simply a definition by the specific author on the Pala page? I’m curious if this is the widely conventional terminology in the colored stone industry at large and what an original reference source might be. I know many have written on the subject.

The reason I ask is I used to teach design and there are slightly different definitions that I am familiar with the description of color.

Hue – the position on any given color wheel, or the visible spectrum
Chroma – the purity, or intensity of color
Tint – Color and White (subtractive color mixing)
Tone – Color and Grey (subtractive color mixing)
Shade – Color and Black (subtractive color mixing)
Value – The degree from light to dark

Of course any description of color in gemstones must take into account the nature of additive color mixing and the transmission of light.

To me the presence of “grey” or “brown” would not be the tone, but the degree away from purity of color – or a lower chroma. Low chroma might describe an orange stone with brown, or a blue stone with a neutralizing color presence - Sometimes referred to as a modifier.

I find all this fascinating, especially the conventions used to describe color.

Kindest Regards,

Jeffrey Hunt

 

[T L]

Hue Tone and Saturation

I have a question about the definition of color in gemstones inspired by Chrono in an earlier post. Specifically, the definition of Hue, Tone, and Saturation in the following link:

http://www.palagems.com/quality_4cs.htm#color

My question for the experts here - Is this generally accepted terminology for colored stones or simply a definition by the specific author on the Pala page? I’m curious if this is the widely conventional terminology in the colored stone industry at large and what an original reference source might be. I know many have written on the subject.

The reason I ask is I used to teach design and there are slightly different definitions that I am familiar with the description of color.

Hue – the position on any given color wheel, or the visible spectrum
Chroma – the purity, or intensity of color
Tint – Color and White (subtractive color mixing)
Tone – Color and Grey (subtractive color mixing)
Shade – Color and Black (subtractive color mixing)
Value – The degree from light to dark

Of course any description of color in gemstones must take into account the nature of additive color mixing and the transmission of light.

To me the presence of “grey” or “brown” would not be the tone, but the degree away from purity of color – or a lower chroma. Low chroma might describe an orange stone with brown, or a blue stone with a neutralizing color presence - Sometimes referred to as a modifier.

I find all this fascinating, especially the conventions used to describe color.

Kindest Regards,

Jeffrey Hunt

I go by the GIA gemsets, and I think that is widely accepted in the trade. Yes, tone is a separate thing from saturation, but tone does affect saturation or "chroma" because if a stone is too light or dark in tone, it loses saturation. A long time ago, I used to think that dark toned stones were the best because I confused tone with saturation, and I suspect a lot of newbies to gem collecting do the same thing as well. Unfortunately, the GIA gemset does not give enough ranges of saturation for each hue, but it is a simplistic method. GIA describes brown and grey as modifiers and cool hues tend to show grey, and warm stones tend to show brown, which differs a bit from what you described above, but it's the same general concept.

If you think of color as a three dimensional thing, then tone, saturation, and hue are the dimensions, and there can be an infinite arrangement of these three dimensions. This is unrealistic for grading purposes, and hence the reason GIA has simplified it with only about 5 or 6 (I forget) levels for satuaration, and another limited amount for tone and hue.

 

[Jeffrey Hunt]

Hi,

TL thank you for the reply. I found the GIA definitions on this page: http://www.gia.edu/research-resources/gia-gem-database/data-acquisition.html Click Color Description.

Tone - I see the GIA definition as the one that is most inadvertently misused. GIA describes it as the lightness or darkness of a stone - simply. I did not find another reference to tone as describing color, also, a change in hue or saturation of course would change tone.

Gemwizard http://www.gemewizard.com/ Is this the gemwizard software you refer too? It's very fun and useful, but in the demo I see no method to view stones that move towards grey or brown or modified. Perhaps the full version takes this into account.

http://www.gemewizard.com/download_gemesquare.php There is indication in the video that once you start the stone color comparison process that you can match a brown garnet or example, simply by matching and narrowing down the choices. Does this work well in practice?

This is also interesting reading that additionally defines color conventions in gemstones: http://www.gemguide.com/news/GMN200705.htm This also implies that different labs may have different systems.

Kind Regards,

Jeff

 

[T L]

Hi,

TL thank you for the reply. I found the GIA definitions on this page: http://www.gia.edu/research-resources/gia-gem-database/data-acquisition.html Click Color Description.

Tone - I see the GIA definition as the one that is most inadvertently misused. GIA describes it as the lightness or darkness of a stone - simply. I did not find another reference to tone as describing color, also, a change in hue or saturation of course would change tone.

Gemwizard http://www.gemewizard.com/ Is this the gemwizard software you refer too? It's very fun and useful, but in the demo I see no method to view stones that move towards grey or brown or modified. Perhaps the full version takes this into account.

http://www.gemewizard.com/download_gemesquare.php There is indication in the video that once you start the stone color comparison process that you can match a brown garnet or example, simply by matching and narrowing down the choices. Does this work well in practice?

This is also interesting reading that additionally defines color conventions in gemstones: http://www.gemguide.com/news/GMN200705.htm This also implies that different labs may have different systems.

Kind Regards,

Jeff

I like the idea of gemewizard, but unfortunately not everyone's monitors are properly calibrated to see online representations of hue,tone and saturation. Gemewizard has failed for me when some vendors tried to describe a color. The actual GIA gemset was probably better since most eyes can be trusted to see the colors of a real object, and not one in virtual world of a computer monitor. Also, one must remember that the species of gemstone dictates what GIA or AGL would deem vivid saturation. A vivid red spinel will never ever be the same as a vivid red Burmese ruby of top color, nor will a tsavorite green be the same as an emerald green. RI, internal silk, and chemical content have a lot to do with what the eye sees. Mr. Zeolite is the resident genius on this information as far as I'm concerned. His background in physics helps to explain the concepts of light and color in a very scientific way.