When you really delve into color you find that there is no such thing as "white".
The basic definition of white being "a combination of all wavelengths of light" - is more a puzzle than a solution.
The human eye has the remarkable ability to adjust to the lightest color in a scene and, barring any saturated tones, consider it white. The only time we realize that what we thought was white was actually say, very light blue, is when we see that color in comparison with another version of white. This then is where the confusion takes place.
You can read from a link below about how we measure white in terms of a theoretical body which is heated (black body), and how "white" can range in color from reddish, through yellowish, and finally into blue. With this in mind, imagine the following scenario:
- You have an image on your computer screen. You have dutifully calibrated the screen to 5000K (which you may know is a yellowish version of white) and profiled the screen properly. You print that image on your carefully profiled printer on paper you consider white and then hold it up next to the computer screen in your office (the nice one you worked so hard to get, with the corner windows). Do they look the same? Probably not.
Well, there are tons of possible reasons why they don't look the same but lets stick to the discussion at hand.
The whitest point in your image when it is displayed on your monitor will be that 5000K yellowish white. If that was all you had to look at, your visual system would adjust and things would be fine. But, consider the print. The whitest point in your image when printed is a complicated thing. First, there's the paper. It may be a very white paper you purchased but white, when referring to paper, really describes how much of the light striking it gets reflected, and how much absorbed. If the amount reflected is distributed evenly across the visible spectrum, then it will appear to be white. Or will it?
It will appear to be close in color to the light striking it. And so enters another part of the riddle. The light striking it (in your nice office) is a mixture of daylight, overhead fluorescent lighting, and that cool designer lamp on your desk. This is the part of the system that you need to control if you want to be able to hold a print up to the screen and see anything resembling similar color.