Luminous Landscape Forum
Raw & Post Processing, Printing => Colour Management => Topic started by: lightshiner on May 20, 2015, 08:46:16 am
-
Can a JPEG image with an embedded colour profile still contain image colours that are outside of that profile (i.e. out of gamut)? In other words, is the embedded colour profile ancillary information that doesn't directly limit the image data (i.e. equivalent to using an external colour profile but embedded)?
- David
-
The file doesn't "contain" colors, it contains numbers 0 - 255. The profile determines what those numbers mean, what colors they represent.
Out of gamut means lower than 0 or higher than 255 in any color channel, which isn't possible.
Jpeg or otherwise is irrelevant.
-
The file doesn't "contain" colors, it contains numbers 0 - 255. The profile determines what those numbers mean, what colors they represent.
Out of gamut means lower than 0 or higher than 255 in any color channel, which isn't possible.
Jpeg or otherwise is irrelevant.
Thanks for the clarification. I interpret your comments to mean that, since the (embedded) colour profile defines the gamut, any coordinate (triplet of numbers) specifying a colour must be included in that gamut.
- David
-
A profile can certainly define some (R,G,B) triplets as "colors" which cannot be displayed on a particular monitor or printed by a particular printer. Can it also define "colors" outside the range of human vision? Or is there some definition or convention which limits the color space which can be defined by a profile?
-
Can it also define "colors" outside the range of human vision?
ProPhoto RGB defines device values (not colors since we can't see them) that fall outside the range of human vision.
-
A profile can certainly define some (R,G,B) triplets as "colors" which cannot be displayed on a particular monitor or printed by a particular printer. Can it also define "colors" outside the range of human vision? Or is there some definition or convention which limits the color space which can be defined by a profile?
See https://en.wikipedia.org/wiki/ProPhoto_RGB_color_space (https://en.wikipedia.org/wiki/ProPhoto_RGB_color_space).
Look at the 2nd figure down (click on it to enlarge it if necessary). You can see that sRGB and Adobe RGB are both fully contained within the gamut of human colours, so all possible RGB combinations of values for these colour spaces fall within the range of human vision.
ProPhoto RGB goes beyond, but as Andrew says, values that lie outside the gamut of human vision aren't colours. That doesn't mean they're ultra violet or infra red or whatever - values outside the horseshoe shape don't represent any wavelength or combination of wavelengths. They're mathematical anomalies, if you like.
It's rather like talking of a temperature of -1 Kelvin. You can write down that number, but it doesn't represent a temperature, as temperature can't physically go below 0 Kelvin.
-
It's rather like talking of a temperature of -1 Kelvin. You can write down that number, but it doesn't represent a temperature, as temperature can't physically go below 0 Kelvin.
really ? http://www.nature.com/news/quantum-gas-goes-below-absolute-zero-1.12146
-
Well, I deliberately left out Quantum Color from my reply (where colors can be out of gamut for a fraction of second)...but you have to be real quick to catch it... ;D
-
really ? http://www.nature.com/news/quantum-gas-goes-below-absolute-zero-1.12146
Yes, I read that story too. Very interesting. But to a rough approximation, can we agree that (quantum effects excepted), temperatures below 0K are not defined?