Color numbers


Doug Schafer
 

We all use color numbers frequently.

I made an observation about color wheels and Lab color pickers...

Color wheels tend to start at Red = 0 and divide the spectrum wheel into 360 degrees. But windows 10 and Corel Painter use 255 divisions instead of 360 and Painter starts with Blue = 0.  Thus Painter and windows have same numbers, but offset.

Further, my Lab color pickers (some even in the same program such as Ps) yield different numbers for same colors (started with RGB numbered samples). Not sure why nor which to believe now. Seems similar to issue of looking at .jpg images with different viewers = different results. For now I'm sticking to native Ps as the "correct" numbers for Lab.

So I made a spreadsheet and attached for your use/review...in hopes someone has an answer or can point to clarifying info??? for Lab picker numbers. Comparing numbers, they are not round-off errors, they are different; tho visually the colors are very close. I calibrate my monitors to D65, 120 cd/m2.

Doug Schafer


Raymond St. Arnaud <starnaud@...>
 

One quick comment, Win 10, Painter and Photoshop and a myriad of other programs, all use 256 units, 0 to 255 = 256 units. Count 0 as a unit as it has a real value

Raymond St Arnaud


From: "k d" <k_d@...>
To: "colortheory" <colortheory@groups.io>
Sent: Saturday, May 16, 2020 4:07:42 PM
Subject: [colortheory] Color numbers

We all use color numbers frequently.

I made an observation about color wheels and Lab color pickers...

Color wheels tend to start at Red = 0 and divide the spectrum wheel into 360 degrees. But windows 10 and Corel Painter use 255 divisions instead of 360 and Painter starts with Blue = 0.  Thus Painter and windows have same numbers, but offset.

Further, my Lab color pickers (some even in the same program such as Ps) yield different numbers for same colors (started with RGB numbered samples). Not sure why nor which to believe now. Seems similar to issue of looking at .jpg images with different viewers = different results. For now I'm sticking to native Ps as the "correct" numbers for Lab.

So I made a spreadsheet and attached for your use/review...in hopes someone has an answer or can point to clarifying info??? for Lab picker numbers. Comparing numbers, they are not round-off errors, they are different; tho visually the colors are very close. I calibrate my monitors to D65, 120 cd/m2.

Doug Schafer